# WHAT WORKS IN CONSERVATION

# What Works in Conservation 2019

*Edited by William J. Sutherland, Lynn V. Dicks, Nancy Ockendon, Silviu O. Petrovan and Rebecca K. Smith*

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© 2019 William J. Sutherland

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Sutherland, W.J., Dicks, L.V., Ockendon, N., Petrovan, S.O., and Smith, R.K. *What Works in Conservation 2019*. Cambridge, UK: Open Book Publishers, 2019. https://doi.org/10.11647/ OBP.0179

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ISSN 2059-4232 (Print) ISSN 2059-4240 (Online)

ISBN Paperback: 978-1-78374-762-7 ISBN Hardback: 978-1-78374-763-4 ISBN Digital (PDF): 978-1-78374-764-1 ISBN Digital ebook (epub): 978-1-78374-765-8 ISBN Digital ebook (mobi): 978-1-78374-766-5 ISBN Digital (XML): 978-1-78374-767-2 DOI: 10.11647/OBP.0179

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# Contents





















































This book has been created to help you make decisions about practical conservation management by providing an assessment, from the available scientific evidence, of what works and what does not work in conservation. It also tells you if no evidence has been found about whether or not a conservation intervention is effective. This is the 2019 edition of *What Works in Conservation*, which was first published in 2015 and is updated annually.

## Who is *What Works in Conservation* for?

This book is for people who have to make decisions about how best to support or conserve biodiversity. These include land managers, conservationists in the public or private sector, farmers, campaigners, advisors or consultants, policymakers, researchers or people taking action to protect local wildlife. *What Works in Conservation* and the associated synopses summarize scientific evidence relevant to conservation objectives and the actions that could be taken to achieve them. *What Works in Conservation* also provides an assessment of the effectiveness of interventions based on available evidence.

We do not aim to make decisions for people, but to support decisionmaking by providing what evidence there is (or is not) about the effects that your planned actions could have. It is important that you read the full details of the evidence, freely available online at www.conservationevidence.com, before making any decisions about implementing an intervention.

## The Conservation Evidence project

The Conservation Evidence project has four parts, all of which are available from our website conservationevidence.com:

1. An ever-expanding searchable **database of over 5,500 summaries**  of previously published scientific papers, reports, reviews or systematic reviews that document the effects of interventions.


Alongside this project, the Centre for Evidence-Based Conservation (http:// www.cebc.bangor.ac.uk) and the Collaboration for Environmental Evidence (http://www.environmentalevidence.org) carry out and compile systematic reviews of evidence on the effectiveness of particular conservation interventions. We recommend carrying out a systematic review, which is more comprehensive than our summaries of evidence, when decisions have to be made with particularly important consequences. Systematic reviews are included in the Conservation Evidence database.

## Which conservation interventions are included?

Lists of interventions for each synopsis are developed and agreed in partnership with an advisory board made up of international conservationists and academics with expertise in the subject. We aim to include all actions that have been carried out or advised for the conservation of the specific group of species or habitat or for the specific conservation issue.

The lists of interventions are organized into categories based on the International Union for the Conservation of Nature (IUCN) classifications of direct threats and conservation actions (https://www.iucnredlist.org/ resources/classification-schemes). Interventions are primarily grouped

according to the relevant direct threats. However, some interventions can be used in response to many different threats and so these have been grouped according to conservation action.

## How we review the literature

We gather evidence by searching relevant scientific journals from volume one through to the most recent volume. Thirty general conservation journals are regularly searched by Conservation Evidence. Specialist journals are also searched for each synopsis (248 have been searched so far). We also search reports, unpublished literature and evidence provided by our advisory boards. Two of the synopses used systematic mapping exercises undertaken by, or in partnership with, other institutions. Systematic mapping uses a rigorous search protocol (involving an array of specified search terms) to retrieve studies from several scientific databases. Evidence published in languages other than English is included when it is identified. Evidence from all around the world is included in synopses. One exception is farmland conservation, which only covers northern Europe (all European countries west of Russia, but not those south of France, Switzerland, Austria, Hungary and Romania). Any apparent bias towards evidence from some regions in a particular synopsis reflects the current biases in published research papers available to Conservation Evidence.

The criteria for inclusion of studies in the Conservation Evidence database are as follows:


These criteria exclude studies examining the effects of specific interventions without actually doing them. For example, predictive modelling studies and studies looking at species distributions in areas with long-standing management histories (correlative studies) are excluded. Such studies can suggest that an intervention could be effective, but do not provide direct evidence of a causal relationship between the intervention and the observed biodiversity pattern.

For each study we summarise the results that are relevant to each intervention. Unless specifically stated, results reflect statistical tests performed on the data within the papers.

## What does *What Works in Conservation* include?

*What Works in Conservation* includes **only the key messages from each synopsis**, which provide a rapid overview of the evidence. These messages are condensed from the summary text for each intervention within each synopsis. **For the full text and references see www. conservationevidence.com**

Panels of experts have assessed the collated evidence for each intervention to determine effectiveness, certainty of the evidence and, in most cases, whether there are negative side-effects (harms). Using these assessments, interventions are categorized based on a combination of effectiveness (the size of benefit or harm) and certainty (the strength of the evidence). The following categories are used: Beneficial, Likely to be beneficial, Trade-off between benefit and harms, Unknown effectiveness, Unlikely to be beneficial, Likely to be ineffective or harmful (for more details see below).

#### Expert assessment of the evidence

The average of several experts' opinions has been shown to be a more reliable and accurate assessment than the opinion of a single expert. We therefore ask a panel of experts to use their judgement to assess whether evidence within the synopsis indicates that an intervention is effective or not. They are also asked to assess how certain they are of the effectiveness given the quality of evidence available for that intervention (certainty of the evidence). Negative side-effects described in the collated evidence are also assessed (harms). They base their assessment solely on the evidence in the synopsis. We use a modified Delphi method to quantify the effectiveness and certainty of evidence of each intervention, based on the summarized evidence. The Delphi method is a structured process that involves asking a panel of experts to state their individual opinion on a subject by scoring anonymously. They can then revise their own scores after seeing a summary of scores and comments from the rest of the panel. Final scores are then collated. Scores and comments are kept anonymous throughout the process so that participants are not overly influenced by any single member of the panel.

For each intervention, experts are asked to read the summarized evidence in the synopsis and then score to indicate their assessment of the following:

**Effectiveness:** 0 = no effect, 100% = always effective.

The score uses an assessment by independent experts of the effectiveness of this action based on the summarized evidence (0% = not effective, 100% = highly effective). This score is based on the direction and size of the effects reported in each study. Actions with high scores typically have large, desirable effects on the target species/habitat in each study. There is some variation between actions, e.g. 100% effectiveness in adding underpasses under roads for bat conservation will likely have different impacts to 100% effectiveness in restoring marsh habitat. The effectiveness score does not consider the quantity or quality of studies; a single, poorly designed study could generate a high effectiveness score. The effectiveness score is combined with the certainty and harms scores to determine the overall effectiveness category (for more details see https://www.conservationevidence.com/ content/page/79)

**Certainty of the evidence**: 0 = no evidence, 100% = high quality evidence; complete certainty. This is certainty of effectiveness of intervention, not of harms.

An assessment by independent experts of the certainty of the evidence for this action based on the summarized evidence (0% = no evidence, 100% = high quality evidence). How certain can we be that the effectiveness score applies to all targets of the intervention (e.g. all birds for an action in the bird synopsis)? This score is based on the number, quality and coverage (species, habitats, geographical locations) of studies. Actions with high scores are supported by lots of well-designed studies with a broad coverage relative to the scope of the intervention. However, the definition of "lots" and "well-designed" will vary between interventions and synopses depending on the breadth of the subject. The certainty score is combined with the effectiveness and harms scores to determine the overall effectiveness category.

**Harms**: 0 = none, 100% = major negative side-effects to the group of species/ habitat of concern.

An assessment by independent experts of the harms of this action to the target group of species/habitat, based on the summarized evidence (0% = none, 100% = major undesirable effects). Undesirable effects on other groups of species/habitats are not considered in this score. The harms score is combined with the effectiveness and certainty scores to determine the overall effectiveness category.

## Categorization of interventions

After one or two rounds of initial scoring, interventions are categorized by their effectiveness, as assessed by the expert panel. The median score from all the experts' assessments is calculated for the effectiveness, certainty and harms for each intervention. Categorization is based on these median values i.e. on a combination of the size of the benefit and harm and the strength of the evidence. The table and figure overleaf show how interventions are categorized using the median scores. There is an important distinction between lack of benefit and lack of evidence of benefit.

Once interventions are categorized, experts are given the chance to object if they believe an intervention has been categorized incorrectly. Interventions that receive a specified number (depending on the size of the panel) of strong objections from experts are re-scored by the expert panel and re-categorized accordingly. Experts did not see the categories for the farmland synopsis or for the 'Reduce predation by other species' section of the bird synopsis and so those categories are based on the second round of scoring.

## How to use *What Works in Conservation*

Please remember that the categories provided in this book are meant as a guide and a starting point in assessing the effectiveness of conservation interventions. The assessments are based on the available evidence for the target group of species for each intervention and may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence, in order to assess their relevance to your species or system. Full details of the evidence are available at www. conservationevidence.com.

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in our assessment. A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.


#### **Table of categories of effectiveness**

Categories of effectiveness based on a combination of effectiveness (the size of the benefit and harm) and certainty (the strength of the evidence). The top graph refers to interventions with harms <20% and the bottom graph to interventions with harms ≥20%.

# 1. AMPHIBIAN CONSERVATION

#### **Rebecca K. Smith, Helen Meredith & William J. Sutherland**

#### **Expert assessors**

**Ariadne Angulo**, Co-Chair of the Amphibian Specialist Group, Peru **Robert Brodman**, Saint Joseph's College, Indiana, USA **Andrew Cunningham**, Institute of Zoology, Zoological Society of London, UK **Jeff Dawson**, Durrell Wildlife Conservation Trust, UK **Rob Gandola**, University of Southampton, UK **Jaime García Moreno**, International Union for Conservation of Nature, The Netherlands **Trent Garner**, Institute of Zoology, Zoological Society of London, UK **Richard Griffiths**, Durrell Institute of Conservation and Ecology, UK **Sergei Kuzmin**, Russian Academy of Sciences **Michael Lanoo**, Indiana University, USA **Michael Lau**, WWF-Hong Kong **James Lewis**, Amphibian Survival Alliance/Global Wildlife Conservation, USA **An Martel**, Ghent University, Belgium **LeGrand Nono Gonwouo**, Cameroon Herpetology-Conservation Biology Foundation **Deanna Olson**, US Forest Service **Timo Paasikunnas**, Curator of Conservation at Helsinki Zoo, Finland **Frank Pasmans**, Ghent University, Belgium **Silviu Petrovan**, Froglife, UK **Carlos Martínez Rivera**, Philadelphia Zoo, USA **Gonçalo Rosa**, Institute of Zoology, Zoological Society of London, UK **David Sewell**, Durrell Institute of Conservation and Ecology, UK **Rebecca K. Smith**, University of Cambridge, UK **Ben Tapley**, Herpetology Department, Zoological Society of London, UK **Jeanne Tarrant**, Endangered Wildlife Trust, South Africa **Karthikeyan Vasudevan**, Wildlife Institute of India **Victor Wasonga**, National Museums of Kenya **Ché Weldon**, North-West University, South Africa **Sally Wren**, Amphibian Specialist Group Programme Officer, New Zealand

**Scope of assessment**: for native wild amphibian species across the world.

**Assessed:** 2014.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects to the group of species of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

> Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 1.1 Threat: Residential and commercial development


### **Unknown effectiveness (limited evidence)**

## **Legal protection of species**

Three reviews, including one systematic review, in the Netherlands and UK found that legal protection of amphibians was not effective at protecting populations during development. Two reviews found that the number of great crested newt mitigation licences issued in England and Wales increased over 10 years. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 35%; harms 7%).*

## **No evidence found (no assessment)**


# 1.2.1 Engage farmers and other volunteers


## **Likely to be beneficial**

## **Engage landowners and other volunteers to manage land for amphibians**

Three studies, including one replicated and one controlled study, in Estonia, Mexico and Taiwan found that engaging landowners and other volunteers in habitat management increased amphibian populations and axolotl weight. Six studies in Estonia, the USA and UK found that up to 41,000 volunteers were engaged in habitat restoration programmes for amphibians and restored up to 1,023 ponds or 11,500 km2 of habitat. *Assessment: likely to be beneficial (effectiveness 70%; certainty 55%; harms 5%).*

http://www.conservationevidence.com/actions/777

### **Pay farmers to cover the costs of conservation measures**

Four of five studies, including two replicated studies, in Denmark, Sweden and Taiwan found that payments to farmers increased amphibian populations, numbers of species or breeding habitat. One found that amphibian habitat was not maintained. *Assessment: likely to be beneficial (effectiveness 70%; certainty 53%; harms 10%).*

http://www.conservationevidence.com/actions/818

## 1.2.2 Terrestrial habitat management

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for terrestrial habitat management in agricultural systems?**


### **Manage silviculture practices in plantations**

Studies investigating the effects of silviculture practices are discussed in 'Threat: Biological resource use — Logging and wood harvesting'.

### **Unknown effectiveness (limited evidence)**

### **Manage cutting regime**

One before-and-after study in Australia found that restoration that included reduced mowing increased numbers of frog species. *Assessment for 'Change mowing regime' from 'Habitat restoration and creation' section: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/788

### **Manage grazing regime**

Two studies, including one replicated, controlled study, in the UK and USA found that grazed plots had lower numbers of toads than ungrazed plots and that grazing, along with burning, decreased numbers of amphibian species. Five studies, including four replicated studies, in Denmark, Estonia and the UK found that habitat management that included reintroduction of grazing maintained or increased toad populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 39%; harms 10%).*

http://www.conservationevidence.com/actions/780

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 1.2.3 Aquatic habitat management

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for aquatic habitat management in agricultural systems?**


### **Likely to be beneficial**

### **Manage ditches**

One controlled, before-and-after study in the UK found that managing ditches increased toad numbers. One replicated, site comparison study in the Netherlands found that numbers of amphibians and species were higher in ditches managed under agri-environment schemes compared to those managed conventionally. *Assessment: likely to be beneficial (effectiveness 71%; certainty 60%; harms 0%).*

## **Likely to be ineffective or harmful**

## **Exclude domestic animals or wild hogs from ponds by fencing**

Four replicated studies, including one randomized, controlled, beforeand-after study, in the USA found that excluding livestock from streams or ponds did not increase overall numbers of amphibians, species, eggs or larval survival, but did increase larval and metamorph abundance. One before-and-after study in the UK found that pond restoration that included livestock exclusion increased pond use by breeding toads. *Assessment: likely to be ineffective or harmful (effectiveness 31%; certainty 50%; harms 25%).*

# 1.3 Threat: Energy production and mining


#### **Unknown effectiveness (limited evidence)**

### **Artificially mist habitat to keep it damp**

One before-and-after study in Tanzania found that installing a sprinkler system to mitigate against a reduction of river flow did not maintain a population of Kihansi spray toads. *Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 20%; harms 0%).*

# 1.4 Threat: Transportation and service corridors


## **Likely to be beneficial**

### **Close roads during seasonal amphibian migration**

Two studies, including one replicated study, in Germany found that road closure sites protected large numbers of amphibians from mortality during breeding migrations. *Assessment: likely to be beneficial (effectiveness 85%; certainty 50%; harms 0%).*

## **Modify gully pots and kerbs**

One before-and-after study in the UK found that moving gully pots 10 cm away from the kerb decreased the number of great crested newts that fell in by 80%. *Assessment: likely to be beneficial (effectiveness 80%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/782

### **Trade-off between benefit and harms**

## **Install barrier fencing along roads**

Seven of eight studies, including one replicated and two controlled studies, in Germany, Canada and the USA found that barrier fencing with culverts decreased amphibian road deaths, in three cases depending on fence design. One study found that few amphibians were diverted by barriers. *Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 68%; harms 23%).*

http://www.conservationevidence.com/actions/756

#### **Install culverts or tunnels as road crossings**

Thirty-two studies investigated the effectiveness of installing culverts or tunnels as road crossings for amphibians. Six of seven studies, including three replicated studies, in Canada, Europe and the USA found that installing culverts or tunnels decreased amphibian road deaths. One found no effect on road deaths. Fifteen of 24 studies, including one review, in Australia, Canada, Europe and the USA found that tunnels were used by amphibians. Four found mixed effects depending on species, site or culvert type. Five found that culverts were not used or were used by less than 10% of amphibians. Six studies, including one replicated, controlled study, in Canada, Europe and the USA investigated the use of culverts with flowing water. Two found that they were used by amphibians. Three found that they were rarely or not used. Certain culvert designs were found not to be suitable for amphibians. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 75%; harms 25%).*

## **Unknown effectiveness (limited evidence)**

## **Use signage to warn motorists**

One study in the UK found that despite warning signs and human assistance across roads, some toads were still killed on roads. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/841

## **Unlikely to be beneficial**

### **Use humans to assist migrating amphibians across roads**

Three studies, including one replicated study, in Italy and the UK found that despite assisting toads across roads during breeding migrations, toads were still killed on roads and 64–70% of populations declined. Five studies in Germany, Italy and the UK found that large numbers of amphibians were moved across roads by up to 400 patrols. *Assessment: unlikely to be beneficial (effectiveness 35%; certainty 40%; harms 3%).*

# 1.5 Threat: Biological resource use

## 1.5.1 Hunting and collecting terrestrial animals


## **Likely to be beneficial**

### **Reduce impact of amphibian trade**

One review found that reducing trade through legislation allowed frog populations to recover from over-exploitation. *Assessment: likely to be beneficial (effectiveness 76%; certainty 40%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Use legislative regulation to protect wild populations**

One review found that legislation to reduce trade resulted in the recovery of frog populations. One study in South Africa found that the number of permits issued for scientific and educational use of amphibians increased from 1987 to 1990. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 30%; harms 5%).*

http://www.conservationevidence.com/actions/785

### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 1.5.2 Logging and wood harvesting


## **Likely to be beneficial**

## **Retain riparian buffer strips during timber harvest**

Six replicated and/or controlled studies in Canada and the USA compared amphibian numbers following clearcutting with or without riparian buffer strips. Five found mixed effects and one found that abundance was higher with riparian buffers. Two of four replicated studies, including one randomized, controlled, before-and-after study, in Canada and the USA found that numbers of species and abundance were greater in wider buffer strips. Two found no effect of buffer width. *Assessment: likely to be beneficial (effectiveness 50%; certainty 61%; harms 10%).*

http://www.conservationevidence.com/actions/747

#### **Use shelterwood harvesting instead of clearcutting**

Three studies, including two randomized, replicated, controlled, beforeand-after studies, in the USA found that compared to clearcutting, shelterwood harvesting resulted in higher or similar salamander abundance. One meta-analysis of studies in North America found that partial harvest, which included shelterwood harvesting, resulted in smaller reductions in salamander populations than clearcutting. *Assessment: likely to be beneficial (effectiveness 40%; certainty 57%; harms 10%).*

http://www.conservationevidence.com/actions/851

#### **Trade-off between benefit and harms**

#### **Leave coarse woody debris in forests**

Two replicated, controlled studies in the USA found that abundance was similar in clearcuts with woody debris retained or removed for eight of nine amphibian species, but that the overall response of amphibians was more negative where woody debris was retained. Two replicated, controlled studies in the USA and Indonesia found that the removal of coarse woody debris from standing forest did not affect amphibian diversity or overall amphibian abundance, but did reduce species richness. One replicated, controlled study in the USA found that migrating amphibians used clearcuts where woody debris was retained more than where it was removed. One replicated, site comparison study in the USA found that within clearcut forest, survival of juvenile amphibians was significantly higher within piles of woody debris than in open areas. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 60%; harms 26%).*

http://www.conservationevidence.com/actions/843

## **Unknown effectiveness (limited evidence)**

#### **Use patch retention harvesting instead of clearcutting**

We found no evidence for the effect of retaining patches of trees rather than clearcutting on amphibian populations. One replicated study in Canada found that although released red-legged frogs did not move towards retained tree patches, large patches were selected more and moved out of less than small patches. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/847

## **Unlikely to be beneficial**

#### **Leave standing deadwood/snags in forests**

One randomized, replicated, controlled, before-and-after study in the USA found that compared to total clearcutting, leaving dead and wildlife trees did not result in higher abundances of salamanders. One randomized, replicated, controlled study in the USA found that numbers of amphibians and species were similar with removal or creation of dead trees within forest. *Assessment: unlikely to be beneficial (effectiveness 5%; certainty 58%; harms 2%).*

http://www.conservationevidence.com/actions/845

#### **Use leave-tree harvesting instead of clearcutting**

Two studies, including one randomized, replicated, controlled, beforeand-after study, in the USA found that compared to clearcutting, leaving a low density of trees during harvest did not result in higher salamander abundance. *Assessment: unlikely to be beneficial (effectiveness 10%; certainty 48%; harms 11%).*

#### **Likely to be ineffective or harmful**

#### **Harvest groups of trees instead of clearcutting**

Three studies, including two randomized, replicated, controlled, beforeand-after studies, in the USA found that harvesting trees in small groups resulted in similar amphibian abundance to clearcutting. One meta-analysis and one randomized, replicated, controlled, before-and-after study in North America and the USA found that harvesting, which included harvesting groups of trees, resulted in smaller reductions in salamander populations than clearcutting. *Assessment: likely to be ineffective or harmful (effectiveness 33%; certainty 60%; harms 23%).*

http://www.conservationevidence.com/actions/844

#### **Thin trees within forests**

Six studies, including five replicated and/or controlled studies, in the USA compared amphibians in thinned to unharvested forest. Three found that thinning had mixed effects and one found no effect on abundance. One found that amphibian abundance increased following thinning but the body condition of ensatina salamanders decreased. One found a negative overall response of amphibians. Four studies, including two replicated, controlled studies, in the USA compared amphibians in thinned to clearcut forest. Two found that thinning had mixed effects on abundance and two found higher amphibian abundance or a less negative overall response of amphibians following thinning. One meta-analysis of studies in North America found that partial harvest, which included thinning, decreased salamander populations, but resulted in smaller reductions than clearcutting. *Assessment: likely to be ineffective or harmful (effectiveness 35%; certainty 60%; harms 40%).*

# 1.6 Threat: Human intrusions and disturbance

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for human intrusions and disturbance? No evidence found (no assessment)** ● Use signs and access restrictions to reduce disturbance

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Use signs and access restrictions to reduce disturbance

# 1.7 Threat: Natural system modifications


#### **Beneficial**

#### **Regulate water levels**

Three studies, including one replicated, site comparison study, in the UK and USA found that maintaining pond water levels, in two cases with other habitat management, increased or maintained amphibian populations or increased breeding success. One replicated, controlled study in Brazil found that keeping rice fields flooded after harvest did not change amphibian abundance or numbers of species, but changed species composition. One replicated, controlled study in the USA found that draining ponds increased abundance and numbers of amphibian species. *Assessment: beneficial (effectiveness 70%; certainty 65%; harms 10%).*

http://www.conservationevidence.com/actions/833

#### **Unknown effectiveness (limited evidence)**

#### **Mechanically remove mid-storey or ground vegetation**

One randomized, replicated, controlled study in the USA found that mechanical understory reduction increased numbers of amphibian species, but not amphibian abundance. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/781

#### **Likely to be ineffective or harmful**

#### **Use herbicides to control mid-storey or ground vegetation**

Three studies, including two randomized, replicated, controlled studies, in the USA found that understory removal using herbicide had no effect or negative effects on amphibian abundance. One replicated, site comparison study in Canada found that following logging, abundance was similar or lower in stands with herbicide treatment and planting compared to those left to regenerate naturally. *Assessment: likely to be ineffective or harmful (effectiveness 10%; certainty 50%; harms 50%).*

http://www.conservationevidence.com/actions/778

## **Use prescribed fire or modifications to burning regime (forests)**

Eight of 15 studies, including three randomized, replicated, controlled studies, in Australia, North America and the USA found no effect of prescribed forest fires on amphibian abundance or numbers of species. Four found that fires had mixed effects on abundance. Four found that abundance, numbers of species or hatching success increased and one that abundance decreased. *Assessment: likely to be ineffective or harmful (effectiveness 30%; certainty 58%; harms 40%).*

## **Use prescribed fire or modifications to burning regime (grassland)**

Two of three studies, including one replicated, before-and-after study, in the USA and Argentina found that prescribed fires in grassland decreased amphibian abundance or numbers of species. One found that spring, but not autumn or winter burns in grassland, decreased abundance. *Assessment: likely to be ineffective or harmful (effectiveness 10%; certainty 40%; harms 70%).*

# 1.8 Threat: Invasive and other problematic species

# 1.8.1 Reduce predation by other species


### **Beneficial**

## **Remove or control fish by drying out ponds**

One before-and-after study in the USA found that draining ponds to eliminate fish increased numbers of amphibian species. Four studies, including one review, in Estonia, the UK and USA found that pond drying to eliminate fish, along with other management activities, increased amphibian abundance, numbers of species and breeding success. *Assessment: beneficial (effectiveness 80%; certainty 66%; harms 3%).*

http://www.conservationevidence.com/actions/826

#### **Likely to be beneficial**

#### **Remove or control fish population by catching**

Four of six studies, including two replicated, controlled studies, in Sweden, the USA and UK found that removing fish by catching them increased amphibian abundance, survival and recruitment. Two found no significant effect on newt populations or toad breeding success. *Assessment: likely to be beneficial (effectiveness 50%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/827

#### **Remove or control invasive bullfrogs**

Two studies, including one replicated, before-and-after study, in the USA and Mexico found that removing American bullfrogs increased the size and range of frog populations. One replicated, before-and-after study in the USA found that following bullfrog removal, frogs were found out in the open more. *Assessment: likely to be beneficial (effectiveness 79%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/825

#### **Remove or control invasive viperine snake**

One before-and-after study in Mallorca found that numbers of Mallorcan midwife toad larvae increased after intensive, but not less intensive, removal of viperine snakes. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/830

#### **Remove or control mammals**

One controlled study in New Zealand found that controlling rats had no significant effect on numbers of Hochstetter's frog. Two studies, one of which was controlled, in New Zealand found that predator-proof enclosures enabled or increased survival of frog species. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/839

#### **Trade-off between benefit and harms**

#### **Remove or control fish using Rotenone**

Three studies, including one replicated study, in Sweden, the UK and USA found that eliminating fish using rotenone increased numbers of amphibians, amphibian species and recruitment. One review in Australia, the UK and USA found that fish control that included using rotenone increased breeding success. Two replicated studies in Pakistan and the UK found that rotenone use resulted in frog deaths and negative effects on newts. *Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 60%; harms 52%).*

http://www.conservationevidence.com/actions/828

#### **Unknown effectiveness (limited evidence)**

#### **Exclude fish with barriers**

One controlled study in Mexico found that excluding fish using a barrier increased weight gain of axolotls. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/829

#### **No evidence found (no assessment)**


## 1.8.2 Reduce competition with other species



#### **Unknown effectiveness (limited evidence)**

### **Reduce competition from native amphibians**

One replicated, site comparison study in the UK found that common toad control did not increase natterjack toad populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/821

## **Remove or control invasive Cuban tree frogs**

One before-and-after study in the USA found that removal of invasive Cuban tree frogs increased numbers of native frogs. *Assessment: unknown effectiveness — limited evidence (effectiveness 65%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/822

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Remove or control invasive cane toads.

## 1.8.3 Reduce adverse habitat alteration by other species


## **Likely to be beneficial**

### **Control invasive plants**

One before-and-after study in the UK found that habitat and species management that included controlling swamp stonecrop, increased a population of natterjack toads. One replicated, controlled study in the USA found that more Oregon spotted frogs laid eggs in areas where invasive reed canarygrass was mown. *Assessment: likely to be beneficial (effectiveness 60%; certainty 47%; harms 0%).*

http://www.conservationevidence.com/actions/823

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Prevent heavy usage/exclude wildfowl from aquatic habitat.

## 1.8.4 Reduce parasitism and disease – chytridiomycosis


## **Likely to be beneficial**

#### **Use temperature treatment to reduce infection**

Four of five studies, including four replicated, controlled studies, in Australia, Switzerland and the USA found that increasing enclosure or water temperature to 30–37°C for over 16 hours cured amphibians of chytridiomycosis. One found that treatment did not cure frogs. *Assessment: likely to be beneficial (effectiveness 60%; certainty 70%; harms 10%).*

http://www.conservationevidence.com/actions/770

#### **Trade-off between benefit and harms**

#### **Use antifungal treatment to reduce infection**

Twelve of 16 studies, including four randomized, replicated, controlled studies, in Europe, Australia, Tasmania, Japan and the USA found that antifungal treatment cured or increased survival of amphibians with chytridiomycosis. Four studies found that treatments did not cure chytridiomycosis, but did reduce infection levels or had mixed results. Six of the eight studies testing treatment with itraconazole found that it was effective at curing chytridiomycosis. One found that it reduced infection levels and one found mixed effects. Six studies found that specific fungicides caused death or other negative side effects in amphibians. *Assessment: tradeoffs between benefits and harms (effectiveness 71%; certainty 70%; harms 50%).*

http://www.conservationevidence.com/actions/882

### **Unknown effectiveness (limited evidence)**

## **Add salt to ponds**

One study in Australia found that following addition of salt to a pond containing the chytrid fungus, a population of green and golden bell frogs remained free of chytridiomycosis for over six months. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 25%; harms 50%).*

http://www.conservationevidence.com/actions/762

### **Immunize amphibians against infection**

One randomized, replicated, controlled study in the USA found that vaccinating mountain yellow-legged frogs with formalin-killed chytrid fungus did not significantly reduce chytridiomycosis infection rate or mortality. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/765

#### **Remove the chytrid fungus from ponds**

One before-and-after study in Mallorca found that drying out a pond and treating resident midwife toads with fungicide reduced levels of infection but did not eradicate chytridiomycosis. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 25%; harms 0%).*

## **Sterilize equipment when moving between amphibian sites**

We found no evidence for the effects of sterilizing equipment when moving between amphibian sites on the spread of disease between amphibian populations or individuals. Two randomized, replicated, controlled study in Switzerland and Sweden found that Virkon S disinfectant did not affect survival, mass or behaviour of eggs, tadpoles or hatchlings. However, one of the studies found that bleach significantly reduced tadpole survival. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 30%; harms 40%).*

http://www.conservationevidence.com/actions/768

## **Treating amphibians in the wild or pre-release**

One before-and-after study in Mallorca found that treating wild toads with fungicide and drying out the pond reduced infection levels but did not eradicate chytridiomycosis. *Assessment: unknown effectiveness — limited evidence (effectiveness 27%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/767

## **Use gloves to handle amphibians**

We found no evidence for the effects of using gloves on the spread of disease between amphibian populations or individuals. A review for Canada and the USA found that there were no adverse effects of handling 22 amphibian species using disposable gloves. However, three replicated studies in Australia and Austria found that deaths of tadpoles were caused by latex, vinyl and nitrile gloves for 60–100% of species tested. *Assessment: unknown effectiveness — limited evidence (effectiveness 9%; certainty 35%; harms 65%).*

http://www.conservationevidence.com/actions/769

#### **Unlikely to be beneficial**

#### **Use antibacterial treatment to reduce infection**

Two studies, including one randomized, replicated, controlled study, in New Zealand and Australia found that treatment with chloramphenicol antibiotic, with other interventions in some cases, cured frogs of chytridiomycosis. One replicated, controlled study found that treatment with trimethoprim-sulfadiazine increased survival time but did not cure infected frogs. *Assessment: unlikely to be beneficial (effectiveness 38%; certainty 45%; harms 10%).*

http://www.conservationevidence.com/actions/763

## **Use antifungal skin bacteria or peptides to reduce infection**

Three of four randomized, replicated, controlled studies in the USA found that introducing antifungal bacteria to the skin of chytrid infected amphibians did not reduce infection rate or deaths. One found that it prevented infection and death. One randomized, replicated, controlled study in the USA found that adding antifungal skin bacteria to soil significantly reduced chytridiomycosis infection rate in salamanders. One randomized, replicated, controlled study in Switzerland found that treatment with antimicrobial skin peptides before or after infection with chytridiomycosis did not increase toad survival. *Assessment: unlikely to be beneficial (effectiveness 29%; certainty 50%; harms 10%).*

http://www.conservationevidence.com/actions/764

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Use zooplankton to remove zoospores

## 1.8.5 Reduce parasitism and disease – ranaviruses


#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Sterilize equipment to prevent ranaviruses.

# 1.9.1 Agricultural pollution


#### **Unknown effectiveness (limited evidence)**

### **Create walls or barriers to exclude pollutants**

One controlled study in Mexico found that installing filters across canals to improve water quality and exclude fish increased weight gain in axolotls. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 29%; harms 0%).*

http://www.conservationevidence.com/actions/771

## **Plant riparian buffer strips**

One replicated, controlled study in the USA found that planting buffer strips along streams did not increase amphibian abundance or numbers of species. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 30%; harms 0%).*

## **Reduce pesticide, herbicide or fertilizer use**

One study in Taiwan found that halting pesticide use, along with habitat management, increased a population of frogs. *Assessment: unknown effectiveness — limited evidence (effectiveness 71%; certainty 26%; harms 0%).*

http://www.conservationevidence.com/actions/832

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Prevent pollution from agricultural lands or sewage treatment facilities entering watercourses

## 1.9.2 Industrial pollution


#### **Trade-off between benefit and harms**

#### **Add limestone to water bodies to reduce acidification**

Five before-and-after studies, including one controlled, replicated study, in the Netherlands and UK found that adding limestone to ponds resulted in establishment of one of three translocated amphibian populations, a temporary increase in breeding and metamorphosis by natterjack toads and increased egg and larval survival of frogs. One replicated, site comparison study in the UK found that habitat management that included adding limestone to ponds increased natterjack toad populations. However, two before-and-after studies, including one controlled study, in the UK found that adding limestone to ponds resulted in increased numbers of abnormal

eggs, high tadpole mortality and pond abandonment. *Assessment: trade-offs between benefits and harms (effectiveness 47%; certainty 50%; harms 50%).*

http://www.conservationevidence.com/actions/748

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Augment ponds with ground water to reduce acidification.

# 1.10 Threat: Climate change and severe weather


### **Create microclimate and microhabitat refuges**

Studies investigating the effects of creating refuges are discussed in 'Habitat restoration and creation' and 'Threat: Biological resource use — Leave coarse woody debris in forests'.

### **Maintain ephemeral ponds**

Studies investigating the effects of regulating water levels and deepening ponds are discussed in 'Threat: Natural system modifications — Regulate water levels' and 'Habitat restoration and creation — Deepen, de-silt or re-profile ponds'.

## **Beneficial**

## **Deepen ponds to prevent desiccation**

Four studies, including one replicated, controlled study, in France, Denmark and the UK found that pond deepening and enlarging or re-profiling resulted in establishment or increased populations of amphibians. Four before-andafter studies in Denmark and the UK found that pond deepening, along with other interventions, maintained newt or increased toad populations. *Assessment for 'Deepen, de-silt or re-profie ponds' from* 'Habitat restoration and creation' section*: beneficial (effectiveness 71%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/806

#### **Unknown effectiveness (limited evidence)**

#### **Use irrigation systems for amphibian sites**

One before-and-after study in Tanzania found that installing a sprinkler system to mitigate against a reduction of river flow did not maintain a population of Kihansi spray toads. *Assessment for 'Artificially mist habitat to keep it damp' from 'Threat: Energy production and mining' section: unknown effectiveness — limited evidence (effectiveness 24%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/804

#### **No evidence found (no assessment)**


# 1.11 Habitat protection


### **Trade-off between benefit and harms**

#### **Retain buffer zones around core habitat**

Two studies, including one replicated, controlled study, in Australia and the USA found that retaining unmown buffers around ponds increased numbers of frog species, but had mixed effects on tadpole mass and survival. One replicated, site comparison study in the USA found that retaining buffers along ridge tops within harvested forest increased salamander abundance, body condition and genetic diversity. However, one replicated study in the USA found that 30 m buffer zones around wetlands were not sufficient to protect marbled salamanders. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 50%; harms 25%).*

## **Unknown effectiveness (limited evidence)**

## **Protect habitats for amphibians**

One replicated, site comparison study in the UK found that statutory level habitat protection helped protect natterjack toad populations. One beforeand-after study in the UK found that protecting a pond during development had mixed effects on populations of amphibians. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 31%; harms 9%).*

http://www.conservationevidence.com/actions/820

## **Retain connectivity between habitat patches**

One before-and-after study in Australia found that retaining native vegetation corridors maintained populations of frogs over 20 years. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 31%; harms 0%).*

# 1.12 Habitat restoration and creation

## 1.12.1 Terrestrial habitat

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for terrestrial habitat restoration and creation?**


## **Beneficial**

## **Replant vegetation**

Four studies, including one replicated study, in Australia, Spain and the USA found that amphibians colonized replanted forest, reseeded grassland and seeded and transplanted upland habitat. Three of four studies, including two replicated studies, in Australia, Canada, Spain and the USA found that areas planted with trees or grass had similar amphibian abundance or community composition to natural sites and one found similar or lower abundance compared to naturally regenerated forest. One found that wetlands within reseeded grasslands were used less than those in natural grasslands. One before-and-after study in Australia found that numbers of frog species increased following restoration that included planting shrubs and trees. *Assessment: beneficial (effectiveness 70%; certainty 63%; harms 3%).*

http://www.conservationevidence.com/actions/849

#### **Likely to be beneficial**

### **Clear vegetation**

Seven studies, including four replicated studies, in Australia, Estonia and the UK found that vegetation clearance, along with other habitat management and in some cases release of amphibians, increased or maintained amphibian populations or increased numbers of frog species. However, great crested newt populations were only maintained for six years, but not in the longer term. *Assessment: likely to be beneficial (effectiveness 60%; certainty 54%; harms 10%).*

http://www.conservationevidence.com/actions/761

### **Create artificial hibernacula or aestivation sites**

Two replicated studies in the UK found that artificial hibernacula were used by two of three amphibian species and along with other terrestrial habitat management maintained populations of great crested newts. *Assessment: likely to be beneficial (effectiveness 50%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/759

## **Create refuges**

Two replicated, controlled studies, one of which was randomized, in the USA and Indonesia found that adding coarse woody debris to forest floors had no effect on the number of amphibian species or overall abundance, but had mixed effects on abundance of individual species. One before-andafter study in Australia found that restoration that included reintroducing coarse woody debris to the forest floor increased frog species. Three studies, including two replicated studies, in New Zealand, the UK and USA found that artificial refugia were used by amphibians and, along with other interventions, maintained newt populations. *Assessment: likely to be beneficial (effectiveness 45%; certainty 55%; harms 0%).*

## **Restore habitat connectivity**

One before-and-after study in Italy found that restoring habitat connectivity by raising a road on a viaduct significantly decreased amphibian deaths. *Assessment: likely to be beneficial (effectiveness 75%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/840

## **Unknown effectiveness (limited evidence)**

## **Change mowing regime**

One before-and-after study in Australia found that restoration that included reduced mowing increased numbers of frog species. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/783

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Create habitat connectivity.

## 1.12.2 Aquatic habitat

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for aquatic habitat restoration and creation?**



## **Beneficial**

## **Create ponds (amphibians in general)**

Twenty-eight studies investigated the colonization of created ponds by amphibians in general, all of which found that amphibians used all or some of the created ponds. Five of nine studies in Australia, Canada, Spain, the UK and USA found that numbers of species were similar or higher in created compared to natural ponds. Nine studies in Europe and the USA found that amphibians established stable populations, used or reproduced in created ponds. Four found that species composition differed, and abundance, juvenile productivity or size in created ponds depended on species. One study found that numbers of species were similar or lower in created ponds. Sixteen studies in Europe and the USA found that created ponds were used or colonized by up to 15 naturally colonizing species, up to 10 species that reproduced or by captive-bred amphibians. Five studies in Europe and the USA found that pond creation, with restoration in three cases, maintained and increased populations or increased species. *Assessment: beneficial (effectiveness 80%; certainty 80%; harms 0%).*

#### **Create ponds (frogs)**

Six of nine studies in Australia, Italy, Spain, the UK and USA found that frogs established breeding populations or reproduced in created ponds. One study in Denmark found that frogs colonized created ponds. One study in the Netherlands found that pond creation, along with vegetation clearance, increased frog populations. One study in the USA found that survival increased with age of created ponds. *Assessment: beneficial (effectiveness 75%; certainty 70%; harms 0%).*

http://www.conservationevidence.com/actions/865

#### **Create ponds (natterjack toads)**

Five studies in the UK and Denmark found that pond creation, along with other interventions, maintained or increased populations at 75–100% of sites. One study in the UK found that compared to natural ponds, created ponds had lower tadpole mortality from desiccation, but higher mortality from predation by invertebrates. *Assessment: beneficial (effectiveness 75%; certainty 70%; harms 10%).*

http://www.conservationevidence.com/actions/866

#### **Create ponds (salamanders including newts)**

Three studies in France, Germany and the USA found that alpine newts, captive-bred smooth newts and translocated spotted salamanders established stable breeding populations in 20–100% of created ponds. Three studies in France, China and the USA found that alpine newts, Chinhai salamanders and translocated spotted salamanders, but not tiger salamanders, reproduced in created ponds. *Assessment: beneficial (effectiveness 70%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/867

#### **Create wetlands**

Fifteen studies, including one review and seven replicated studies, in Australia, Kenya and the USA, investigated the effectiveness of creating wetlands for amphibians. Six studies found that created wetlands had similar amphibian abundance, numbers of species or communities as natural wetlands or in one case adjacent forest. Two of those studies found that created wetlands had fewer amphibians, amphibian species and

#### **Deepen, de-silt or re-profile ponds**

Four studies, including one replicated, controlled study, in France, Denmark and the UK found that pond deepening and enlarging or re-profiling resulted in establishment or increased populations of amphibians. Four before-andafter studies in Denmark and the UK found that pond deepening, along with other interventions, maintained newt or increased toad populations. *Assessment: beneficial (effectiveness 71%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/817

#### **Restore wetlands**

Seventeen studies, including one review and 11 replicated studies, in Canada, Taiwan and the USA, investigated the effectiveness of wetland restoration for amphibians. Seven of ten studies found that amphibian abundance, numbers of species and species composition were similar in restored and natural wetlands. Two found that abundance or numbers of species were lower and species composition different to natural wetlands. One found mixed results. One global review found that in 89% of cases, restored and created wetlands had similar or higher amphibian abundance or numbers of species to natural wetlands. Seven of nine studies found that wetland restoration increased numbers of amphibian species, with breeding populations establishing in some cases, and maintained or increased abundance of individual species. Three found that amphibian abundance or numbers of species did not increase with restoration. Three of the studies found that restored wetlands were colonized by up to eight amphibian species. *Assessment: beneficial (effectiveness 80%; certainty 73%; harms 0%).*

## **Likely to be beneficial**

## **Create ponds (great crested newts)**

Three studies in Germany and the UK found that great crested newts established breeding populations in created ponds. One systematic review in the UK found that there was no conclusive evidence that mitigation, which often included pond creation, resulted in self-sustaining populations. Four studies in the UK found that great crested newts colonized up to 88% of, or reproduced in 38% of created ponds. *Assessment: likely to be beneficial (effectiveness 60%; certainty 61%; harms 0%).*

http://www.conservationevidence.com/actions/863

### **Create ponds (green toads)**

Two studies in Denmark found that pond creation, along with other interventions, significantly increased green toad populations. One study in Sweden found that green toads used or reproduced in 41–59% of created ponds. *Assessment: likely to be beneficial (effectiveness 73%; certainty 59%; harms 0%).*

http://www.conservationevidence.com/actions/864

#### **Create ponds (toads)**

Five studies in Germany, Switzerland, the UK and USA found that toads established breeding populations or reproduced in 16–100% of created ponds. Two studies in Denmark and Switzerland found that wild but not captive-bred toads colonized 29–100% of created ponds. One study in Denmark found that creating ponds, along with other interventions, increased toad populations. *Assessments: likely to be beneficial (effectiveness 70%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/868

#### **Remove specific aquatic plants**

One before-and-after study in the UK found that habitat and species management that included controlling swamp stonecrop, increased a population of natterjack toads. One replicated, controlled study in the USA found that more Oregon spotted frogs laid eggs in areas where invasive reed canarygrass was mown. *Assessment for 'Control invasive plants' from*  'Threat: Invasive alien and other problematic species': *likely to be beneficial (effectiveness 60%; certainty 47%; harms 0%).*

http://www.conservationevidence.com/actions/815

#### **Restore ponds**

Fifteen studies investigated the effectiveness of pond restoration for amphibians. Three studies, including one replicated, controlled, beforeand-after study in Denmark, the UK and USA found that pond restoration did not increase or had mixed effects on population numbers and hatching success. One replicated, before-and-after study in the UK found that restoration increased pond use. One replicated study in Sweden found that only 10% of restored ponds were used for breeding. Three before-andafter studies, including one replicated, controlled study, in Denmark and Italy found that restored and created ponds were colonized by up to seven species. Eight of nine studies, including one systematic review, in Denmark, Estonia, Italy and the UK found that pond restoration, along with other habitat management, maintained or increased populations, or increased pond occupancy, ponds with breeding success or numbers of amphibian species. One found that numbers of species did not increase and one found that great crested newt populations did not establish. *Assessment: likely to be beneficial (effectiveness 60%; certainty 63%; harms 0%).*

http://www.conservationevidence.com/actions/878

#### **Unknown effectiveness (limited evidence)**

#### **Remove tree canopy to reduce pond shading**

One before-and-after study in the USA found that canopy removal did not increase hatching success of spotted salamanders. One before-and-after study in Denmark found that following pond restoration that included canopy removal, translocated toads established breeding populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 25%; harms 0%).*

## **No evidence found (no assessment)**


Strict protocols should be followed when carrying out these interventions to minimise potential spread of disease-causing agents such as chytrid fungi and Ranavirus.

## 1.13.1 Translocate amphibians


## **Likely to be beneficial**

## **Translocate amphibians (amphibians in general)**

Overall, three global reviews and one study in the USA found that 65% of amphibian translocations that could be assessed resulted in established breeding populations or substantial recruitment to the adult population. A further two translocations resulted in breeding and one in survival following release. One review found that translocations of over 1,000 animals were more successful, but that success was not related to the source of animals (wild or captive), life-stage, continent or reason for translocation. *Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 19%).*

http://www.conservationevidence.com/actions/854

## **Translocate amphibians (great crested newts)**

Four of six studies in the UK found that translocated great crested newts maintained or established breeding populations. One found that populations survived at least one year in 37% of cases, but one found that within three years breeding failed in 48% of ponds. A systematic review of 31 studies found no conclusive evidence that mitigation that included translocations resulted in self-sustaining populations. One review found that newts reproduced following 56% of translocations, in some cases along with other interventions. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 10%).*

http://www.conservationevidence.com/actions/858

### **Translocate amphibians (natterjack toads)**

Three studies in France and the UK found that translocated natterjack toad eggs, tadpoles, juveniles or adults established breeding populations at some sites, although head-started or captive-bred animals were also released at some sites. Re-establishing toads on dune or saltmarsh habitat was more successful than on heathland. One study in the UK found that repeated translocations of wild rather than captive-bred toads were more successful. *Assessment: likely to be beneficial (effectiveness 60%; certainty 56%; harms 10%).*

http://www.conservationevidence.com/actions/859

## **Translocate amphibians (salamanders including newts)**

Four studies in the UK and USA found that translocated eggs or adults established breeding populations of salamanders or smooth newts. One study in the USA found that one of two salamander species reproduced following translocation of eggs, tadpoles and metamorphs. One study in the USA found that translocated salamander eggs hatched and tadpoles had similar survival rates as in donor ponds. *Assessment: likely to be beneficial (effectiveness 70%; certainty 55%; harms 0%).*

### **Translocate amphibians (toads)**

Two of four studies in Denmark, Germany, the UK and USA found that translocating eggs and/or adults established common toad breeding populations. One found populations of garlic toads established at two of four sites and one that breeding populations of boreal toads were not established. One study in Denmark found that translocating green toad eggs to existing populations, along with habitat management, increased population numbers. Four studies in Germany, Italy, South Africa and the USA found that translocated adult toads reproduced, survived up to six or 23 years, or some metamorphs survived over winter. *Assessment: likely to be beneficial (effectiveness 60%; certainty 56%; harms 10%).*

http://www.conservationevidence.com/actions/855

### **Translocate amphibians (wood frogs)**

Two studies in the USA found that following translocation of wood frog eggs, breeding populations were established in 25–50% of created ponds. One study in the USA found that translocated eggs hatched and up to 57% survived as tadpoles in pond enclosures. *Assessment: likely to be beneficial (effectiveness 40%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/856

#### **Trade-off between benefit and harms**

### **Translocate amphibians (frogs)**

Eight of ten studies in New Zealand, Spain, Sweden, the UK and USA found that translocating frog eggs, juveniles or adults established breeding populations. Two found that breeding populations went extinct within five years or did not establish. Five studies in Canada, New Zealand and the USA found that translocations of eggs, juveniles or adults resulted in little or no breeding at some sites. Five studies in Italy, New Zealand and the USA found that translocated juveniles or adults survived the winter or up to eight years. One study in the USA found that survival was lower for Oregon spotted frogs translocated as adults compared to eggs. Two studies in the USA found that 60–100% of translocated frogs left the release site and 35–73% returned to their original pond within 32 days. Two studies in found that frogs either lost or gained weight after translocation. *Assessment: trade-offs between benefits and harms (effectiveness 58%; certainty 65%; harms 20%).*

http://www.conservationevidence.com/actions/861

## 1.13.2 Captive breeding, rearing and releases


## **Likely to be beneficial**

## **Release captive-bred individuals (amphibians in general)**

One review found that 41% of release programmes of captive-bred or headstarted amphibians showed evidence of breeding in the wild for multiple generations, 29% showed some evidence of breeding and 12% evidence of survival following release. *Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 10%).*

http://www.conservationevidence.com/actions/871

## **Release captive-bred individuals (frogs)**

Five of six studies in Europe, Hong Kong and the USA found that captivebred frogs released as tadpoles, juveniles or adults established breeding populations and in some cases colonized new sites. Three studies in Australia and the USA found that a high proportion of frogs released as eggs survived to metamorphosis, some released tadpoles survived the first few months, but few released froglets survived. Four studies in Australia, Italy, the UK and USA found that captive-bred frogs reproduced at 31–100% of release sites, or that breeding was limited. *Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 15%).*

http://www.conservationevidence.com/actions/870

### **Trade-off between benefit and harms**

## **Breed amphibians in captivity (frogs)**

Twenty-three of 33 studies across the world found that amphibians produced eggs in captivity. Seven found mixed results, with some species or populations reproducing successfully, but with other species difficult to maintain or raise to adults. Two found that frogs did not breed successfully or died in captivity. Seventeen of the studies found that captive-bred frogs were raised successfully to hatching, tadpoles, froglets or adults in captivity. Four studies in Canada, Fiji, Hong Kong and Italy found that 30–88% of eggs hatched, or survival to metamorphosis was 75%, as froglets was 17–51% or to adults was 50–90%. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 68%; harms 30%).*

## **Breed amphibians in captivity (harlequin toads)**

Four of five studies in Colombia, Ecuador, Germany and the USA found that harlequin toads reproduced in captivity. One found that eggs were only produced by simulating a dry and wet season and one found that breeding was difficult. One found that captive-bred harlequin toads were raised successfully to metamorphosis in captivity and two found that most toads died before or after hatching. *Assessment: trade-offs between benefits and harms (effectiveness 44%; certainty 50%; harms 28%).*

http://www.conservationevidence.com/actions/836

## **Breed amphibians in captivity (Mallorcan midwife toad)**

Two studies in the UK found that Mallorcan midwife toads produced eggs that were raised to metamorphs or toadlets in captivity. However, clutches dropped by males were not successfully maintained artificially. One study in the UK found that toads bred in captivity for nine or more generations had slower development, reduced genetic diversity and predator defence traits. *Assessment: trade-offs between benefits and harms (effectiveness 69%; certainty 55%; harms 40%).*

http://www.conservationevidence.com/actions/837

## **Breed amphibians in captivity (salamanders including newts)**

Four of six studies in Japan, Germany, the UK and USA found that eggs were produced successfully in captivity. Captive-bred salamanders were raised to yearlings, larvae or adults. One review found that four of five salamander species bred successfully in captivity. Four studies in Germany, Mexico and the USA found that egg production, larval development, body condition and survival were affected by water temperature, density or enclosure type. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 50%; harms 25%).*

http://www.conservationevidence.com/actions/838

### **Breed amphibians in captivity (toads)**

Ten studies in Germany, Italy, Spain, the UK and USA found that toads produced eggs in captivity. Eight found that toads were raised successfully to tadpoles, toadlets or adults in captivity. Two found that most died after hatching or metamorphosis. Two reviews found mixed results with four species of toad or 21% of captive populations of Puerto Rican crested toads breeding successfully. Four studies in Germany, Spain and the USA found that reproductive success was affected by tank location and humidity. *Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 60%; harms 25%).*

http://www.conservationevidence.com/actions/848

### **Head-start amphibians for release**

Twenty-two studies head-started amphibians from eggs and monitored them after release. A global review and six of 10 studies in Europe and the USA found that released head-started tadpoles, metamorphs or juveniles established breeding populations or increased existing populations. Two found mixed results with breeding populations established in 71% of studies reviewed or at 50% of sites. Two found that head-started metamorphs or adults did not establish a breeding population or prevent a population decline. An additional 10 studies in Australia, Canada, Europe and the USA measured aspects of survival or breeding success of released headstarted amphibians and found mixed results. Three studies in the USA only provided results for head-starting in captivity. Two of those found that eggs could be reared to tadpoles, but only one successfully reared adults. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 60%; harms 25%).*

http://www.conservationevidence.com/actions/881

## **Release captive-bred individuals (Mallorcan midwife toad)**

Three studies in Mallorca found that captive-bred midwife toads released as tadpoles, toadlets or adults established breeding populations at 38–100% of sites. One study in the UK found that predator defences were maintained, but genetic diversity was reduced in a captive-bred population. *Assessment: trade-offs between benefits and harms (effectiveness 68%; certainty 58%; harms 20%).*

#### **Release captive-bred individuals (toads)**

Two of three studies in Denmark, Sweden and the USA found that captivebred toads released as tadpoles, juveniles or metamorphs established populations. The other found that populations were not established. Two studies in Puerto Rico found that survival of released captive-bred Puerto Rican crested toads was low. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 50%; harms 20%).*

http://www.conservationevidence.com/actions/875

#### **Use artificial fertilization in captive breeding**

Three replicated studies, including two randomized studies, in Australia and the USA found that the success of artificial fertilization depended on the type and number of doses of hormones used to stimulate egg production. One replicated study in Australia found that 55% of eggs were fertilized artificially, but soon died. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 40%; harms 20%).*

http://www.conservationevidence.com/actions/834

#### **Use hormone treatment to induce sperm and egg release**

One review and nine of 10 replicated studies, including two randomized, controlled studies, in Austria, Australia, China, Latvia, Russia and the USA found that hormone treatment of male amphibians stimulated or increased sperm production, or resulted in successful breeding. One found that hormone treatment of males and females did not result in breeding. One review and nine of 14 replicated studies, including six randomized and/ or controlled studies, in Australia, Canada, China, Ecuador, Latvia and the USA found that hormone treatment of female amphibians had mixed results, with 30–71% of females producing viable eggs following treatment, or with egg production depending on the combination, amount or number of doses of hormones. Three found that hormone treatment stimulated egg production or successful breeding. Two found that treatment did not stimulate or increase egg production. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 65%; harms 30%).*

## **Unknown effectiveness (limited evidence)**

## **Release captive-bred individuals (salamanders including newts)**

One study in Germany found that captive-bred great crested newts and smooth newts released as larvae, juveniles and adults established stable breeding populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 70%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/874

## **Unlikely to be beneficial**

#### **Freeze sperm or eggs for future use**

Ten replicated studies, including three controlled studies, in Austria, Australia, Russia, the UK and USA found that following freezing, viability of amphibian sperm, and in one case eggs, depended on species, cryoprotectant used, storage temperature or method and freezing or thawing rate. One found that sperm could be frozen for up to 58 weeks. *Assessment: unlikely to be beneficial (effectiveness 35%; certainty 50%; harms 10%).*

http://www.conservationevidence.com/actions/876

#### **Likely to be ineffective or harmful**

## **Release captive-bred individuals (green and golden bell frogs)**

Three studies in Australia found that captive-bred green and golden bell frogs released mainly as tadpoles did not established breeding populations, or only established breeding populations in 25% of release programmes. One study in Australia found that some frogs released as tadpoles survived at least 13 months. *Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 50%; harms 20%).*

# 1.14 Education and awareness raising


## **Likely to be beneficial**

### **Engage volunteers to collect amphibian data (citizen science)**

Five studies in Canada, the UK and USA found that amphibian data collection projects engaged up to 10,506 volunteers and were active in 16–17 states in the USA. Five studies in the UK and USA found that volunteers surveyed up to 7,872 sites, swabbed almost 6,000 amphibians and submitted thousands of amphibian records. *Assessment: likely to be beneficial (effectiveness 66%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/760

#### **Provide education programmes about amphibians**

One study in Taiwan found that education programmes about wetlands and amphibians, along with other interventions, doubled a population of Taipei frogs. Four studies, including one replicated study, in Germany, Mexico, Slovenia, Zimbabwe and the USA found that education programmes increased the amphibian knowledge of students. *Assessment: likely to be beneficial (effectiveness 58%; certainty 55%; harms 0%).*

http://www.conservationevidence.com/actions/776

## **Raise awareness amongst the general public through campaigns and public information**

Two studies, including one replicated, before-and-after study, in Estonia and the UK found that raising public awareness, along with other interventions, increased amphibian breeding habitat and numbers of toads. One before-and-after study in Mexico found that raising awareness in tourists increased their knowledge of axolotls. However, one study in Taiwan found that holding press conferences had no effect on a frog conservation project. *Assessment: likely to be beneficial (effectiveness 60%; certainty 51%; harms 0%).*

# 2.  BAT CONSERVATION (2019 Update)

#### **Anna Berthinussen, Olivia C. Richardson & John D. Altringham**

#### **Expert assessors**

**Fabio Bontadina**, SWILD — Urban Ecology & Wildlife Research, Switzerland **Jasja Dekker,** Jasja Dekker Dierecologie, Netherlands **Brock Fenton**, University of Western Ontario, Canada **Winifred Frick**, Bat Conservation International, USA **Alice Hughes**, Xishuangbanna Tropical Botanical Garden, UK/China **David Jacobs**, University of Cape Town, South Africa **Johnny de Jong,** Swedish University of Agricultural Sciences, Sweden **Bradley Law**, Forest Science Centre, New South Wales Department of Primary Industries, Australia **Rodrigo Medellin,** National Autonomous University of Mexico**,** Mexico **Kirsty Park**, University of Stirling, UK **Silviu Petrovan,** University of Cambridge, UK **Paul Racey,** University of Exeter, UK **Orly Razgour,** University of Southampton, UK **Guido Reiter**, Austrian Coordination Centre for Bat Conservation and Research, Austria **Danilo Russo**, Federico II University of Naples, Italy **Ricardo Rocha**, University of Cambridge, UK **Emma Stone,** African Bat Conservation, UK/Malawi

**Scope of assessment**: for native wild bat species across the world.

**Assessed:** 2019. For previous assessments and expert panels please check *What Works in Conservation 2018*.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects to the group of species of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 2.1 Threat: Residential and commercial development


## **Likely to be beneficial**

## **Create alternative bat roosts within developments**

Ten studies evaluated the effects of creating alternative bat roosts within developments on bat populations. Two studies were in the USA and eight studies were in Europe.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (10 STUDIES)

Use: (10 studies): Two replicated studies in the USA and UK found that bats did not use any of the alternative roosts provided in bat houses or a purposebuilt bat wall after exclusion from buildings. One review in the USA and two studies (one replicated) in the UK found that bat boxes or bat lofts/barns were used by bats at 13–74% of development sites, and bat lofts/barns were used by maternity colonies at one of 19 development sites. Three of five before-and-after studies in Ireland, Portugal, Spain and the UK found that bat colonies used purpose-built roosts in higher or similar numbers after the original roosts were destroyed. The other two studies found that bats used purpose-built roosts in lower numbers than the original roost.

*Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 10%).* http://www.conservationevidence.com/actions/949

**Unknown effectiveness (limited evidence)**

## **Retain existing bat roosts and access points within developments**

Two studies evaluated the effects of retaining existing bat roosts and access points within developments on bat populations. One study was in Ireland and one study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (2 STUDIES)

Use (2 studies): One before-and-after study in Ireland found similar numbers of brown long-eared bats roosting within an attic after existing access points were retained during renovations. One replicated, beforeand-after study in the UK found that four of nine bat roosts retained within developments were used as maternity colonies, in two cases by similar or greater numbers of bats after development had taken place.

*Assessment: unknown effectiveness (effectiveness 67%; certainty 27%; harms 0%).* http://www.conservationevidence.com/actions/947

## **Relocate access points to bat roosts within developments**

Two studies evaluated the effects of relocating access points to bat roosts within building developments on bat populations. One study was in Ireland and one in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (2 STUDIES)

Use (2 studies): One before-and-after study in Ireland found that fewer brown long-eared bats used a roost after the access points were relocated, and no bats were observed flying through them. One before-and-after study in the UK found that few lesser horseshoe bats used an alternative access point with a 'bend' design to re-enter a roost in a building development, but the number of bats using the roost increased after an access point with a 'straight' design was installed.

*Assessment: unknown effectiveness (effectiveness 45%; certainty 32%; harms 10%).*

http://www.conservationevidence.com/actions/946

### **Change timing of building work**

One study evaluated the effects of changing the timing of building work on bat populations. The study was in Ireland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One before-and-after study in Ireland found that carrying out roofing work outside of the bat maternity season, along with retaining bat access points, resulted in a similar number of brown long-eared bats continuing to use a roost within an attic.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 12%; harms 0%).* http://www.conservationevidence.com/actions/950

## **Exclude bats from roosts during building work**

One study evaluated the effects of excluding bats from roosts during building work on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Behaviour change (1 study): One replicated, before-and-after study in the UK found that excluding bats from roosts within buildings did not change roost switching frequency, core foraging areas or foraging preferences of soprano pipistrelle colonies.

*Assessment: unknown effectiveness (effectiveness 45%; certainty 23%; harms 17%).*

http://www.conservationevidence.com/actions/1930

## **Create or restore bat foraging habitat in urban areas**

Three studies evaluated the effects of creating or restoring bat foraging habitat in urban areas on bat populations. One study in the USA evaluated restored forest fragments, and two studies in the UK and the USA evaluated green roofs.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, controlled, site comparison study in the USA found no difference in species richness over green roofs and conventional unvegetated roofs.

#### POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): One site comparison study in the USA found higher bat activity (relative abundance) in two of seven restored forest fragments in urban areas than in two unrestored forest fragments. One replicated, controlled, site comparison study in the UK found significantly greater bat activity over 'biodiverse' green roofs than conventional unvegetated roofs, but not over 'sedum' green roofs. One replicated, controlled, site comparison study in the USA found greater bat activity for three of five bat species over green roofs than over conventional unvegetated roofs.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 60%; certainty 36%; harms 0%).*

http://www.conservationevidence.com/actions/954

#### **Protect brownfield or ex-industrial sites**

One study evaluated the effects of protecting brownfield or ex-industrial sites on bat populations. The study was in the USA.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One study in the USA found that five bat species were recorded within a protected urban wildlife refuge on an abandoned manufacturing site.

#### POPULATION RESPONSE (0 STUDIES)

USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/953

#### **Legally protect bats during development**

Three studies evaluated the effects of legally protecting bats by issuing licences during development on bat populations. The three studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (0 STUDIES)

#### OTHER (3 STUDIES)

Impact on bat roost sites (2 studies): One review in the UK found that licenced activities during building developments had a negative impact on bat roosts, with 68% of roosts being destroyed. One replicated, before-andafter study in the UK found that five of 28 compensation roosts provided under licence were used, and two by similar or greater numbers of bats after development.

#### *Bat Conservation*

Change in human behaviour (2 studies): One review in the UK found that the number of development licences for bats more than doubled over three years in Scotland. One review in the UK found that 81% of licensees did not carry out post-development monitoring to assess whether bats used the roost structures installed.

*Assessment: unknown effectiveness (effectiveness 18%; certainty 15%; harms 2%).* https://www.conservationevidence.com/actions/1935

## **No evidence found (no assessment)**


## 2.2.1 All farming systems


## **Likely to be beneficial**

### **Use organic farming instead of conventional farming**

Seven studies evaluated the effects of using organic farming instead of conventional farming on bat populations. Six studies were in Europe and one in the USA.

#### *Bat Conservation*

#### COMMUNITY RESPONSE (4 STUDIES)

Richness/diversity (4 studies): Three of four replicated paired sites or site comparison studies in the UK, USA and France found that the number of bat species did not differ between organic and non-organic farms. The other study found more bat species on organic farms than non-organic farms.

#### POPULATION RESPONSE (7 STUDIES)

Abundance (7 studies): Four of five replicated, paired sites or site comparison studies in Europe and the USA found that total bat activity (relative abundance) and common pipistrelle activity did not differ between organic and non-organic farms. The other study found significantly higher total bat activity on organic farms than non-organic farms. Two replicated, paired sites and site comparison studies in the UK found significantly higher activity of *Myotis* species over water and rivers on organic farms than non-organic farms, but no differences were found for other species or habitats.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 41%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/961

## **Retain remnant forest or woodland on agricultural land**

Six studies evaluated the effects of retaining forest or woodland on agricultural land on bat populations. Four studies were in Australia, one in the UK, and one in Brazil.

#### COMMUNITY RESPONSE (4 STUDIES)

Community composition (2 studies): One of two replicated, site comparison studies in Australia and Brazil found that remnant woodland had a different composition of bat species to plantations and treeless paddocks. The other study found that bat species composition was similar between remnant forest and plantations.

Richness/diversity (4 studies): Three of four replicated, site comparison studies in Australia and Brazil found more bat species in remnant forest and woodland than in plantations or treeless paddocks or pasture. The other study found a similar number of bat species in remnant forest, plantations and paddocks.

#### POPULATION RESPONSE (6 STUDIES)

Abundance (6 studies): Five replicated, site comparison studies in Australia, the UK and Brazil found higher bat activity (relative abundance) or more bats in remnant forest or woodland than in plantations, treeless paddocks or pasture, or on arable land. One replicated study in Australia found higher activity for three of 10 bat species in remnant woodland than in treeless paddocks.

#### USAGE (1 STUDY)

Use (1 study): One replicated, site comparison study in Australia found bats roosting in trees within remnant woodland but not in trees within plantations.

*Assessment: likely to be beneficial (effectiveness 55%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/1947

## **Retain or plant native trees and shrubs amongst crops (agroforestry)**

Seven studies evaluated the effects of retaining or planting native trees and shrubs amongst crops on bat populations. Two studies were in South America, four were in Mexico, and one was in Tanzania.

#### COMMUNITY RESPONSE (7 STUDIES)

Community composition (1 study): One replicated, site comparison study in Tanzania found different compositions of bat species in coffee plantations with different amounts and types of shade cover.

Richness/diversity (7 studies): Four of six replicated, site comparison studies in Columbia, Mexico and Costa Rica found a similar number of bat species in shaded and unshaded coffee plantations, and in coffee plantations with different amounts and types of shade cover. The two other studies found more bat species and higher bat diversity in coffee, cacao and banana plantations with varied shade cover, than in plantations with a single shade species or no shade. One replicated, site comparison study in Tanzania found more bat species in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

#### POPULATION RESPONSE (5 STUDIES)

Abundance (5 studies): Two replicated, site comparison studies in Mexico captured more bats in coffee plantations with varied shade cover than in plantations with a single shade species. One replicated, site comparison study in Mexico found higher activity (relative abundance) of forest bat species in plantations with a varied shade cover than in plantations with a single shade species, but the opposite was true for open habitat bat species.

#### *Bat Conservation*

One replicated, site comparison study in Costa Rica found no difference in the number of bats captured between cacao and banana shade plantations and unshaded monocultures. One replicated, site comparison study in Tanzania found greater bat occurrence in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 0%).* http://www.conservationevidence.com/actions/963

### **Unknown effectiveness (limited evidence)**

#### **Introduce agri-environment schemes**

Three studies evaluated the effects of agri-environment schemes on bat populations. The three studies were in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): Two of three replicated, paired sites study in the UK found that total bat activity (relative abundance) and the activity of six bat species did not differ significantly between farms managed under agrienvironment schemes and those managed conventionally. The other study found significantly lower overall bat activity and activity of pipistrelle species on agri-environment scheme farms than conventional farms.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 35%; certainty 30%; harms 10%).*

http://www.conservationevidence.com/actions/962

#### **Engage farmers and landowners to manage land for bats**

One study evaluated the effects of engaging farmers and landowners to manage land for bats on bat populations. The study was in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One study in the UK found that during a five-year project to engage farmers and landowners to manage land for bats, the overall population of greater horseshoe bats at four maternity roosts in the area increased (but see summary below).

USAGE (0 STUDIES)

OTHER (1 STUDY)

Change in human behaviour (1 study): One study in the UK found that a landowner engagement project resulted in 77 bat-related management agreements covering approximately 6,536 ha of land.

*Assessment: unknown effectiveness (effectiveness 55%; certainty 20%; harms 0%).* http://www.conservationevidence.com/actions/1936

## **Retain unmown field margins**

One study evaluated the effects of retaining unmown field margins on bats populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between unmown field margins managed for wildlife on agri-environment scheme farms and field margins on conventional farms.

USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/1940

#### **Manage hedges to benefit bats**

One study evaluated the effects of managing hedges to benefit bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between hedges managed for wildlife on agri-environment scheme farms and hedges on conventional farms.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 0%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1943

## **Retain existing in-field trees**

Two studies evaluated the effects of retaining existing in-field trees on bat populations. Both studies were in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia found that grazed pasture with scattered trees had more bat species than pasture without trees.

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two replicated studies (one site comparison study) in Australia found that paddocks/pasture with scattered trees had greater overall bat activity (relative abundance) or greater activity for four of 10 bat species than treeless paddocks/pasture.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/1945

## **Create tree plantations on agricultural land to provide roosting and foraging habitat for bats**

Three studies evaluated the effects of creating tree plantations on agricultural land to provide roosting and foraging habitat for bats on bat populations. The three studies were in Australia.

#### COMMUNITY RESPONSE (3 STUDIES)

Richness/diversity (3 studies): Three replicated, site comparison studies in Australia found no difference in the number of bat species in agricultural areas with and without plantations of native trees.

#### POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): Two of three replicated, site comparison studies in Australia found no difference in bat activity (relative abundance) in agricultural areas with and without plantations of native trees. The other study found higher bat activity in plantations next to remnant native vegetation than in isolated plantations or over grazing land. In all three studies, bat activity was lower in plantations compared to original forest and woodland remnants.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 30%; certainty 30%; harms 0%).* http://www.conservationevidence.com/actions/958

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.2.2 Livestock farming


## **Unknown effectiveness (limited evidence)**

## **Remove livestock modifications from water troughs**

One study evaluated the effects of removing livestock modifications from water troughs on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One replicated, paired sites study in the USA found that removing livestock modifications from water troughs resulted in bats drinking from them more frequently.

Behaviour change (1 study): One replicated, paired sites study in the USA found that when livestock modifications were removed from water troughs, bats approached troughs fewer times before successfully drinking from them.

*Assessment: unknown effectiveness (effectiveness 60%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/1951

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.2.3 Perennial, non-timber crops


## **No evidence found (no assessment)**


# 2.3 Threat: Energy production—mining

## 2.3.1 Wind turbines

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for wind turbines?**


#### **Beneficial**

## **Increase the wind speed at which turbines become operational ('cut-in speed') to reduce bat fatalities**

Four studies evaluated the effects of increasing the wind speed at which turbines become operational (cut-in speed) on bat populations. One study was in Canada and three studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (4 STUDIES)

Survival (4 studies): Three randomized, replicated, controlled studies (including one before-and-after study) in Canada and the USA, and one review in the USA found that bat fatalities were significantly reduced when the wind speed at which turbines became operational ('cut-in speed') was increased.

USAGE (0 STUDIES) *Assessment: beneficial (effectiveness 80%; certainty 70%; harms 0%).*

https://www.conservationevidence.com/actions/1960

#### **Likely to be beneficial**

#### **Deter bats from turbines using ultrasound**

Two studies evaluated the effects of deterring bats from wind turbines using ultrasound on bat populations. The two studies were in the USA.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study with a before-and-after trial in the second year in the USA found mixed results. In the first year of the study, 21-51% fewer bats were killed at turbines with an ultrasonic deterrent fitted than at control turbines, but in the second year, from 2% more to 64% fewer bats were killed at turbines with ultrasonic deterrents fitted.

#### USAGE (1 STUDY)

Behaviour change (1 study): One paired sites study in the USA found significantly fewer bats flying near one of two wind turbines with an ultrasonic deterrent compared to turbines without.

*Assessment: likely to be beneficial (effectiveness 40%; certainty 45%; harms 7%).*

http://www.conservationevidence.com/actions/968

## **Prevent turbine blades from turning at low wind speeds to reduce bat fatalities**

Three studies evaluated the effects of preventing turbine blades from turning at low wind speeds on bat populations. Two studies were in Canada and one review was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (3 STUDIES)

Survival (3 studies): Two replicated, controlled before-and-after studies (including one randomized study) in Canada and one review in the USA found that bat fatalities were significantly reduced when turbine blades were prevented from turning at low wind speeds.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 80%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/970

## **Automatically reduce turbine blade rotation when bat activity is high**

Two studies evaluated the effects of automatically reducing turbine blade rotation when bat activity is high on bat populations. One study was in Germany, and one in the USA.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (2 STUDIES)

Survival (2 studies): Two replicated studies (one randomized, controlled and one paired sites study) in Germany and the USA found that automatically reducing the rotation speed of wind turbine blades when bat activity is predicted to be high resulted in significantly fewer bat fatalities for all bat species combined and for little brown bats.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 80%; certainty 55%; harms 0%).*

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.3.2 Mining


## **Unknown effectiveness (limited evidence)**

## **Install and maintain gates at mine entrances to restrict public access**

Four studies evaluated the effects of installing gates at mine entrances on bat populations. Three studies were in the USA and one in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, before-and-after study in the USA found that significantly fewer bat species entered mines after gates were installed.

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, before-and-after study in Australia found fewer bats in mines after gates were installed.

#### USAGE (3 STUDIES)

Use (1 study): One before-and-after study in the USA found that 43 of 47 mines continued to be used 12 years after gates were installed, however bats abandoned four mines with 'ladder' design gates.

Behaviour change (2 studies): Two replicated, before-and-after or site comparison studies in the USA and Australia found that bats at mine entrances circled more and entered mines less after gates were installed.

*Assessment: unknown effectiveness (effectiveness 25%; certainty 30%; harms 20%).*

http://www.conservationevidence.com/actions/1963

#### **Maintain microclimate in closed/abandoned mines**

One study evaluated the effects of maintaining the microclimate in an abandoned mine on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in the USA found that modifying the microclimate of an abandoned mine by closing a man-made entrance resulted in a greater number of bats hibernating within the mine.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 45%; certainty 20%; harms 0%).* https://www.conservationevidence.com/actions/1964

#### **No evidence found (no assessment)**


# 2.4 Threat: Transportation and service corridors


#### **Likely to be beneficial**

#### **Install underpasses as road crossing structures for bats**

Six studies evaluated the effects of installing underpasses or culverts as road crossing structures for bats. Five studies were in Europe and one in Australia.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (0 STUDIES)

#### USAGE (6 STUDIES)

Use (6 studies): Six studies (including four replicated studies) in Germany, Ireland the UK and Australia found that bats used underpasses below roads, and crossed over the roads above them, in varying proportions. One replicated, site comparison study in Australia found that bat species adapted to cluttered habitats used small culverts and underpasses more than bat species adapted to open or edge habitats.

*Assessment: likely to be beneficial (effectiveness 52%; certainty 50%; harms 0%).* http://www.conservationevidence.com/actions/976

### **Install overpasses as road crossing structures for bats**

Three studies evaluated the effects of installing overpasses as road crossing structures for bats. Two studies were in Europe and one in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One site comparison study in Australia found that the same number of bat species were recorded at an overpass and in nearby forest and bushland.

#### POPULATION RESPONSE (0 STUDIES)

#### USAGE (2 STUDIES)

Use (2 studies): One replicated, site comparison study in Ireland found that three bat species used overpasses but up to three-quarters of bats crossed the road below at traffic height. One study in the UK found that an overpass with planters was used by two-thirds of crossing bats, and an unvegetated overpass with a paved road over it was not used by crossing bats.

*Assessment: likely to be beneficial (effectiveness 45%; certainty 42%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Install green bridges as road crossing structures for bats**

One study evaluated the effects of installing green bridges as road crossing structures for bats. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One study in the UK found that a green bridge was used by 97% of bats crossing a road.

*Assessment: unknown effectiveness (effectiveness 70%; certainty 27%; harms 0%).*

http://www.conservationevidence.com/actions/979

## **Divert bats to safe crossing points with plantings or fencing**

One study evaluated the effects of diverting bats using an artificial hedgerow on bat populations. The study was in Switzerland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One controlled, before-and-after study in Switzerland found that up to one fifth of lesser horseshoe bats within a colony flew along an artificial hedgerow to commute.

*Assessment: unknown effectiveness (effectiveness 10%; certainty 10%; harms 5%).* http://www.conservationevidence.com/actions/981

### **Maintain bat roosts in road bridges and culverts**

One study evaluated the effects of maintaining bat roosts within a bridge on bat populations. The study was in Ireland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Use (1 study): One before-and-after study in Ireland found that a maternity colony of Daubenton's bats continued to roost in a road bridge over a river in similar numbers after crevices were retained during repair work.

*Assessment: unknown effectiveness (effectiveness 55%; certainty 20%; harms 0%).* http://www.conservationevidence.com/actions/1966

#### **Unlikely to be beneficial**

## **Install bat gantries or bat bridges as road crossing structures for bats**

Two studies evaluated the effects of installing bat gantries as road crossing structures for bats. Both were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Use (2 studies): Two replicated studies (including one site comparison) in the UK found that fewer bats used bat gantries than crossed the road below at traffic height, and one bat gantry was not used at all.

*Assessment: unlikely to be beneficial (effectiveness 2%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/978

#### **No evidence found (no assessment)**


# 2.5 Threat: Biological resource use

## 2.5.1 Hunting


## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


# 2.5.2 Guano harvesting

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for guano harvesting?**


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Introduce and enforce legislation to regulate the harvesting of bat guano

# 2.5.3 Logging and wood harvesting


## **Likely to be beneficial**

### **Thin trees within forests**

Six studies evaluated the effects of thinning trees within forest and woodland on bat populations. Four studies were in the USA, one study was in Canada, and one in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia recorded the same bat species in thinned and unthinned forest, except for the chocolate wattled bat, which was not recorded in forests with unthinned regrowth.

#### POPULATION RESPONSE (6 STUDIES)

Abundance (6 studies): Four of five replicated, site comparison studies (including two paired sites studies and one controlled study) in the USA and Australia found greater total bat activity (relative abundance) in thinned than unthinned forest. The other study found similar total bat activity in thinned and unthinned stands. One replicated, controlled, site comparison study in Canada found greater activity of silver-haired bats in thinned than unthinned stands, but no difference for little brown bats or long-eared bats.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 55%; certainty 45%; harms 1%).*

http://www.conservationevidence.com/actions/991

#### **Retain forested corridors in logged areas**

Three studies evaluated the effects of retaining forested corridors in logged areas on bat populations. The three studies were in the USA.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 studies): One replicated, site comparison study in the USA found that bat activity (relative abundance) was significantly higher along the edges of forested corridors than in corridor interiors or in adjacent logged stands, which had similar activity levels.

#### USAGE (2 STUDIES)

Use (2 studies): One replicated, site comparison study in the USA found more Seminole bats roosting in forested corridors than logged stands or mature forest. One replicated, site comparison study in the USA found more male but fewer female evening bats roosting in forested corridors than logged stands.

*Assessment: likely to be beneficial (effectiveness 55%; certainty 40%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Use selective or reduced impact logging instead of conventional logging**

Three studies evaluated the effects of using selective or reduced impact logging instead of conventional logging on bat populations. Two studies were in the Neotropics and one study was in Italy.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, controlled, site comparison study in Trinidad found that the composition of bat species differed between selectively logged and conventionally logged forest.

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): A review of 41 studies in the Neotropics found that reduced impact logging had a significantly smaller effect on bat abundance than conventional logging. One replicated, site comparison study in Italy found greater bat activity (relative abundance) at two of three sites that used selective logging techniques to open up the forest canopy rather than leaving the canopy intact.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 58%; certainty 30%; harms 2%).*

http://www.conservationevidence.com/actions/989

### **Use shelterwood cutting instead of clearcutting**

One study evaluated the effects of using shelterwood cutting instead of 'gap release' cutting on bat populations. The study was in Australia. We found no studies that evaluated the effects of shelterwood cutting instead of clearcutting.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Use (1 study): One site comparison study in Australia found more Gould's long-eared bats roosting in remnant trees within forests that had been shelterwood harvested than in forests.

*Assessment: unknown effectiveness (effectiveness 15%; certainty 10%; harms 0%).*

## **Retain residual tree patches in logged areas**

Two studies evaluated the effects of retaining residual tree patches in logged areas on bat populations. The two studies were in Canada.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two replicated, site comparison studies in Canada found no difference in bat activity (relative abundance) along the edges of residual tree patches and the edges of clearcut blocks. One replicated, site comparison study in Canada found that the activity of smaller bat species was higher along the edge of residual tree patches than in the centre of clearcut blocks, but the activity of larger bat species did not differ.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 20%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/995

### **Retain riparian buffers in logged areas**

Two studies evaluated the effects of retaining riparian buffers in logged areas on bat populations. The two studies were in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia found a similar number of bat species in riparian buffers within logged forest, regrowth forest and mature forest.

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Australia found similar total bat activity (relative abundance) in riparian buffers within logged forest, regrowth forest and mature forest.

#### USAGE (1 STUDY)

Use (1 study): One replicated, site comparison study in Australia found that southern forest bats roosted less often in riparian buffers in logged forest than in unlogged forest, but Gould's long-eared bats had a similar number of roosts in riparian buffers in logged forest, remnant trees in logged areas and unlogged forest.

*Assessment: unknown effectiveness (effectiveness 35%; certainty 24%; harms 0%).*

## **No evidence found (no assessment)**


# 2.6 Threat: Human disturbance—caving and tourism


## **Likely to be beneficial**

## **Impose restrictions on cave visits**

Three studies evaluated the effects of imposing restrictions on cave visits on bat populations. One study was in the USA, one in Canada and one in Turkey.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two before-and-after studies in Canada and Turkey found that bat populations within caves increased after restrictions on cave visitors were imposed.

#### USAGE (1 STUDY)

Behaviour change (1 study): One study in the USA found that reducing the number of people within cave tour groups did not have a significant effect on the number of take-offs, landings or overall activity (bat movements) of a cave myotis colony roosting within the cave.

*Assessment: likely to be beneficial (effectiveness 64%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/1002

#### **Trade-off between benefit and harms**

#### **Install and maintain cave gates to restrict public access**

Eleven studies evaluated the effects of installing cave gates on bat populations. Six studies were in the USA and five studies were in Europe.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (7 STUDIES)

Abundance (7 studies): Three of four before-and-after studies (including one replicated study and one controlled study) in the Netherlands, the USA, Spain and Turkey found more or similar numbers of bats in caves and a bunker after gates were installed to restrict public access. The other study found fewer bats in caves after gates were installed. Two before-and-after studies in the USA and Spain found more bats within two caves after the size of the gated entrances were increased. One replicated, before-and-after study in the USA found that installing cave gates resulted in population increases or decreased rates of decline for 13 of 20 colonies of Indiana bat. One replicated, site comparison study in Spain found no difference in the population growth rates of bats roosting in caves with and without cave gates.

Condition (1 study): One site comparison study in the USA found that bats hibernating in a cave with a wall and gate over the entrance lost more body mass than bats in a nearby unmodified cave.

#### USAGE (5 STUDIES)

Use (1 study): One replicated, site comparison study in Spain found no difference in the occupancy rates of bats roosting in caves with and without cave gates.

Behaviour change (4 studies): One replicated, controlled, before-and-after and site comparison study in the USA found that bats at cave entrances circled more and entered caves less after gates were installed. One replicated study in the USA found that bats flew through gates with a funnel design more frequently than gates with a round bar or angle iron design. One randomized, controlled, before-and-after study in the UK found that fewer bats flew through cave gates when the spacing between horizontal bars was reduced. One before-and-after study in the USA found that significantly fewer bats emerged from a cave with a gate installed compared with a cave with a fence.

*Assessment: trade-offs between benefits and harms (effectiveness 70%; certainty 50%; harms 20%).*

http://www.conservationevidence.com/actions/999

#### **Unknown effectiveness (limited evidence)**

## **Install fencing around cave entrances to restrict public access**

Two studies evaluated the effects of installing fencing around cave entrances on bat populations. One study was in the USA and one study was in Spain.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Spain found no difference in the population growth rates of bats roosting in caves with and without fencing or gates installed.

#### USAGE (2 STUDIES)

Use (1 study): One replicated, site comparison study in Spain found no difference in the occupancy rates of bats roosting in caves with and without fencing or gates installed.

Behaviour change (1 study): One controlled, before-and-after study in the USA found that significantly more southeastern myotis bats and gray myotis bats emerged from a cave after a steel gate was replaced with a fence.

*Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1991

## **Restrict artificial lighting in caves and around cave entrances**

One study evaluated the effects of restricting artificial lighting in caves on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Behaviour change (1 study): One controlled study in the USA found that using low intensity white lights or red lights in caves resulted in fewer bat flights than with full white lighting, but the number of bat movements was similar between all three light treatments.

*Assessment: unknown effectiveness (effectiveness 15%; certainty 12%; harms 0%).*

http://www.conservationevidence.com/actions/1994

### **Minimize noise levels within caves**

One study evaluated the effects of minimizing noise levels within caves on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Behaviour change (1 study): One controlled study in the USA found that experimental cave tours with groups that did not talk resulted in fewer bat flights than when groups did talk, but talking did not have an effect on the number of bat movements.

*Assessment: unknown effectiveness (effectiveness 40%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/1995

#### **No evidence found (no assessment)**


# 2.7 Threat: Natural system modification

## 2.7.1 Fire and fire suppression


## **Likely to be beneficial**

#### **Use prescribed burning**

Nine studies evaluated the effects of prescribed burning on bat populations. Eight studies were in the USA and one study was in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Community composition (1 study): One replicated, controlled, beforeand-after, paired sites study in Australia found that the composition of bat species differed between burned and unburned woodland sites.

#### POPULATION RESPONSE (4 STUDIES)

Abundance (4 studies): Two replicated, site comparison studies (including one controlled study) in the USA found that the activity (relative abundance) of open habitat bat species and evening bats increased with the number of prescribed fires, but there was no effect on other bat species, including cluttered habitat bat species. One replicated, controlled, before-and-after, paired sites study in Australia found that prescribed burning resulted in higher overall bat activity. One site comparison study in the USA found that two of seven sites that had been burned alongside other restoration practices had higher bat activity than unrestored sites.

#### USAGE (4 STUDIES)

Use (4 studies): One replicated, controlled before-and-after study in the USA found that more female northern myotis bats roosted in burned than unburned forest. Two replicated, controlled, before-and-after studies in the USA found that fewer female northern myotis bats and male Indiana bats roosted in burned than unburned forest. One replicated study in the USA found that evening bats roosted in burned but not unburned forest.

Behaviour change (2 studies): Two replicated, controlled, site comparison studies in the USA found no difference in roost switching frequency or the distance between roost trees for female northern myotis bats and male Indiana bats in burned and unburned forests. One replicated, controlled, before-and-after study in the USA found that female northern myotis home ranges and core areas did not differ in size between burned and unburned forests, but home ranges were closer to burned forest than unburned forest.

*Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 10%).*

https://www.conservationevidence.com/actions/1006

## 2.7.2 Dams and water management/use


#### **Unknown effectiveness (limited evidence)**

## **Create or maintain small dams to provide foraging and drinking habitat for bats**

One study evaluated the effects of maintaining small dams as foraging and drinking habitat for bats on bat populations. The study was in Portugal.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Portugal found that reservoirs created using small dams had greater activity (relative abundance) of four bat species than the streams feeding into them.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 51%; certainty 20%; harms 0%).* http://www.conservationevidence.com/actions/1997

## **Relocate bat colonies roosting inside dams**

One study evaluated the effects of relocating bat colonies inside dams on bat populations. The study was in Argentina.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One study in Argentina found that almost two-thirds of a large colony of Brazilian free-tailed bats relocated to a different dam compartment five months after being displaced from six compartments where the colony originally roosted.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 5%; certainty 5%; harms 5%).* http://www.conservationevidence.com/actions/1998

# 2.8 Threat: Invasive species and disease

## 2.8.1 Invasive species


#### **found (no assessment)** ● Control harmful invasive bat prey species ● Exclude domestic and feral cats from bat roosts and roost entrances

#### ● Keep domestic cats indoors at night ● Use collar-mounted devices on cats to reduce predation of bats

● Control invasive non-predatory competitors

### **Likely to be beneficial**

**No evidence** 

## **Control invasive predators**

One study evaluated the effects of controlling invasive predators on bat populations. The study was in New Zealand.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Survival (1 study): One replicated, before-and-after study in New Zealand found that controlling ship rats resulted in increased survival probabilities for female long-tailed bats.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 80%; certainty 40%; harms 0%).* http://www.conservationevidence.com/actions/1007

## **Unknown effectiveness (limited evidence)**

## **Control invasive plant species**

One study evaluated the effects of controlling invasive plant species on bat populations. The study was in the USA.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One site comparison study in the USA found that two of seven forest fragments where invasive plant species had been removed alongside other restoration practices had significantly higher bat activity (relative abundance) than two unrestored forest fragments.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/1008

#### **No evidence found (no assessment)**


## 2.8.2 Disease


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Carry out surveillance of bats for early treatment/action to reduce disease/viruses

## 2.8.3 White-nose syndrome


## **Unknown effectiveness (limited evidence)**

## **Modify bat hibernacula environments to increase bat survival**

One study evaluated the effects of modifying hibernacula environments to increase bat survival. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study in the USA found that a greater number of little brown bats infected with the white-nose syndrome fungus survived in hibernation chambers at 4°C than at 10°C.

#### USAGE (1 STUDY)

Behaviour change (1 study): One randomized, replicated, controlled study in the USA found that little brown bats infected with the white-nose syndrome fungus stayed in hibernation for longer in hibernation chambers at 4°C than at 10°C.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 10%).*

https://www.conservationevidence.com/actions/1013

### **Treat bats for infection with white-nose syndrome**

One study evaluated the effects of treating bats with a probiotic bacterium to reduce white-nose syndrome infection. The study was in Canada.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study in Canada found that treating little brown bats with a probiotic bacterium at the time of infection with white-nose syndrome increased survival, but treating bats 21 days prior to infection had no effect.

Condition (1 study): One randomized, replicated, controlled study in Canada found that treating little brown bats with a probiotic bacterium at the time of infection with white-nose syndrome reduced the symptoms of the disease, but treating bats 21 days prior to infection made symptoms worse.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 30%; certainty 25%; harms 10%).*

http://www.conservationevidence.com/actions/2008

#### **No evidence found (no assessment)**


## 2.9.1 Domestic and urban waste water


### **Unknown effectiveness (limited evidence)**

## **Change effluent treatments of domestic and urban waste water**

One study evaluated the effects of different sewage treatments on the activity of foraging bats. The study was in the UK. We found no studies that evaluated the effects of changing effluent treatments of domestic and urban waste water discharged into rivers on bat populations.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in the UK found higher activity (relative abundance) of foraging bats over filter bed sewage treatment works than over active sludge systems.

USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 25%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1014

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.9.2 Agricultural and forestry effluents


## **Likely to be beneficial**

## **Reduce pesticide, herbicide or fertiliser use**

Two studies evaluated the effects of reducing pesticide, herbicide and fertiliser use on bat populations. One study was in Mexico and one study was in Portugal.

#### COMMUNITY RESPONSE (2 STUDIES)

Community composition (1 study): One replicated, site comparison study in Portugal found that farms using few or no chemicals had different compositions of bat species to farms using high chemical inputs.

Richness/diversity (1 study): One site comparison study in Mexico found that coffee agroforestry plantations using few or no chemicals had a higher diversity of insect-eating bat species than plantations with high chemical inputs, but the diversity of fruit and nectar eating bat species did not differ.

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Portugal found that farms using few or no chemicals had higher bat activity (relative abundance) than farms using high chemical inputs.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/2013

#### **Unknown effectiveness (limited evidence)**

### **Plant riparian buffer strips**

One study evaluated the effects of planting riparian buffer strips on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ along waterways with buffer strips on agri-environment scheme farms and waterways on conventional farms.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 5%; certainty 10%; harms 0%).* http://www.conservationevidence.com/actions/2016

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.9.3 Light pollution


#### **Likely to be beneficial**

## **Leave bat roosts, roost entrances and commuting routes unlit**

Three studies evaluated the effects of leaving bat roosts and roost entrances unlit on bat populations. One study was in the UK one in Hungary and one in Sweden.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Condition (1 study): One replicated, controlled study in Hungary found that juvenile bats had a higher body mass and greater forearm length at unlit roosts than at roosts with artificial lighting.

#### USAGE (3 STUDIES)

Use (1 study): One replicated, before-and-after study in Sweden found that all of 13 unlit churches continued to be used by brown long-eared bat colonies over 25 years, but bat colonies abandoned their roosts at 14 of 23 churches that were either partly or fully lit with floodlights.

Behaviour change (2 studies): Two replicated, controlled studies in the UK and Hungary found that more bats emerged and bats emerged earlier and foraged for shorter periods when roosts were left unlit than when they had artificial lighting.

*Assessment: likely to be beneficial (effectiveness 80%; certainty 46%; harms 0%).*

http://www.conservationevidence.com/actions/1017

#### **Avoid illumination of bat commuting routes**

Two studies evaluated the effects of avoiding the illumination of bat commuting routes on bat populations. One study was in the Netherlands and one in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): One replicated, before-and-after study in the Netherlands found similar numbers of pond bats flying along unlit canals and canals illuminated with lamps.

One replicated, controlled study in the UK found greater activity (relative abundance) of lesser horseshoe bats along unlit hedges than along hedges illuminated with streetlights.

#### USAGE (2 STUDIES)

Behaviour change (2 studies): One replicated, before-and-after study in the Netherlands found that 28–96% of pond bats changed their flight paths along canals to avoid light spill from lamps. One replicated, controlled study in the UK found that lesser horseshoe bats were active earlier along unlit hedges than along those illuminated with streetlights.

*Assessment: unknown effectiveness (effectiveness 70%; certainty 49%; harms 0%).*

https://www.conservationevidence.com/actions/2017

#### **Use low intensity lighting**

Two studies evaluated the effects of using low intensity lighting on bat populations. The two studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, randomized, controlled study in the UK found that activity (relative abundance) of lesser horseshoe bats, but not *Myotis* bats, was higher along hedges with medium or low intensity lighting than hedges with high intensity lighting.

#### USAGE (1 STUDY)

Behaviour change (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from two roosts when the intensity of red lights was reduced by placing filters over them.

*Assessment: unknown effectiveness (effectiveness 70%; certainty 50%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

### **Restrict timing of lighting**

One study evaluated the effects of restricting the timing of lighting on bat populations. The study was in France.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in France found that turning off streetlights for part of the night resulted in mixed results for activity (relative abundance), depending on bat species, when compared with leaving streetlights switched on all night.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 38%; certainty 20%; harms 0%).* http://www.conservationevidence.com/actions/1019

# **Avoid illumination of key bat habitats**

One study evaluated the effects of avoiding the illumination of key bat habitats on bat populations. The study was in Italy.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, randomized, before-and-after study in Italy found that unlit water troughs had greater activity (relative abundance) of five of six bat species/species groups than troughs illuminated with artificial light.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 72%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/2018

### **Use UV filters on lights**

One study evaluated the effects of using ultraviolet filters on lights on bat populations. The study was in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One randomized, replicated, controlled study in the UK found that hedges lit with ultraviolet filtered lights had higher soprano pipistrelle, but not common pipistrelle activity (relative abundance) than hedges lit with unfiltered light.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 45%; certainty 22%; harms 0%).*

http://www.conservationevidence.com/actions/1020

## **Use red lighting rather than other lighting colours**

Two studies evaluated the effects of red lighting on bat populations. One study was in the UK and one study was in the Netherlands.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, site comparison study in the Netherlands found that red lighting resulted in higher activity (relative abundance) for one of three bat species groups than white or green lighting.

#### USAGE (1 STUDY)

Behaviour (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from a roost when lit with red light than when lit with white light, but no difference was found between red and blue lights.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/2021

#### **No evidence found (no assessment)**


# 2.9.4 Noise pollution


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 2.9.5 Timber treatments


## **Likely to be ineffective or harmful**

spaces

#### **Restrict timing of treatment**

**(no assessment)**

One study evaluated the effects of restricting the timing of timber treatment application on bat populations. The study was in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Survival (1 study): One replicated, controlled laboratory study in the UK found that treating timber with lindane and pentachlorophenol 14 months prior to exposure by bats increased survival but did not prevent death.

#### USAGE (0 STUDIES)

*Assessment: likely to be ineffective or harmful (effectiveness 5%; certainty 55%; harms 50%).*

http://www.conservationevidence.com/actions/1023

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Use mammal safe timber treatments in roof spaces

# 2.10 Climate change and severe weather


#### **No evidence found (no assessment)**


# 2.11 Habitat protection


### **Unknown effectiveness (limited evidence)**

### **Legally protect bat habitats**

Three studies evaluated the effects of legally protecting bat habitats on bat populations. One study was in the UK, one was in Spain, and one in Europe.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, paired sites study in Europe found that the number of bat species did not differ between protected and unprotected forests.

#### POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): One replicated, site comparison study in the UK found that the activity (relative abundance) of Daubenton's bats was significantly higher over rivers on farms in protected areas than in unprotected areas. One replicated, paired sites study in Europe found that

#### *Bat Conservation*

the activity of common noctule bats was higher in protected forests than unprotected forests, but bat activity overall did not differ.

#### USAGE (1 STUDY)

Use (1 study): One study in Spain found that the distributions of 10 of 11 bat species overlapped with areas designated to protect them significantly more than by chance.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/2045

#### **Conserve roosting sites for bats in old structures or buildings**

Two studies evaluated the effects of conserving roosting sites for bats in old structures or buildings on bat populations. Both studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in the UK found that a greater number of bats hibernated in a railway tunnel after walls with access grilles were installed at the tunnel entrances and wood was attached to the tunnel walls.

#### USAGE (1 STUDY)

Use (1 study): One before-and-after study in the UK found that Natterer's bats used a roost that was 'boxed-in' within a church, but the number of bats using the roost was reduced by half.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/2046

#### **No evidence found (no assessment)**


# 2.12 Habitat restoration and creation



### **Likely to be beneficial**

#### **Create artificial water sources**

Five studies evaluated the effects of creating artificial water sources for bat populations. One study was in Israel, one in the USA, one in Germany, one in South Africa and one in Mexico.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, paired sites study in South Africa found a similar number of bat species over farm ponds and in grassland/crops, trees, vineyards or orchards.

#### POPULATION RESPONSE (5 STUDIES)

Abundance (5 studies): Five replicated studies (including four site comparisons and one paired sites study) in Israel, the USA, Germany, South Africa and Mexico found that bat activity (relative abundance) was similar or higher over reservoirs and waste water treatment pools, heliponds and drainage ditches, retention ponds and farm/cattle ponds compared to over natural wetlands, nearby vineyards, surrounding forest or grassland/crops, trees and orchards.

#### USAGE (0 STUDIES)

*Assessment: likely to be beneficial (effectiveness 70%; certainty 55%; harms 0%).*

https://www.conservationevidence.com/actions/959

#### **Unknown effectiveness (limited evidence)**

## **Create artificial hollows and cracks in trees for roosting bats**

One study evaluated the effects of creating artificial hollows and cracks in trees for roosting bats. The study was in Australia.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Use (1 study): One replicated study in Australia found that eight of 16 artificial hollows cut into trees for bats, birds and marsupials with two different entrance designs were used by roosting long-eared bats.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 23%; harms 0%).*

https://www.conservationevidence.com/actions/2047

## **Conserve roosting sites for bats in old structures or buildings**

Two studies evaluated the effects of conserving roosting sites for bats in old structures or buildings on bat populations. Both studies were in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in the UK found that a greater number of bats hibernated in a railway tunnel after walls with access grilles were installed at the tunnel entrances and wood was attached to the tunnel walls.

#### USAGE (1 STUDY)

Use (1 study): One before-and-after study in the UK found that Natterer's bats used a roost that was 'boxed-in' within a church, but the number of bats using the roost was reduced by half.

*Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).* 

https://www.conservationevidence.com/actions/2046

#### **Reinstate bat roosts in felled tree trunks**

One study evaluated the effects of reinstating a bat roost within a felled tree trunk on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (1 STUDY)

Use (1 study): One before-and-after study in the UK found that a roost reinstated by attaching the felled tree trunk to a nearby tree continued to be used by common noctule bats as a maternity roost.

*Assessment: unknown effectiveness (effectiveness 35%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/2048

#### **Create artificial caves or hibernacula for bats**

Two studies evaluated the effects of creating artificial caves or hibernacula for bats on bat populations. Both studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Uptake (1 study): One study in the UK found that the number of bats using an artificial hibernaculum increased in each of nine years after it was built.

Use (2 studies): One study in the UK found that an artificial cave was used by a small number of brown long-eared bats. One study in the UK found that an artificial hibernaculum was used by four bat species.

*Assessment: unknown effectiveness (effectiveness 55%; certainty 22%; harms 0%).* https://www.conservationevidence.com/actions/2049

#### **Restore or create forest or woodland**

Two studies evaluated the effects of restoring forests on bat populations. One study was in Brazil and one in Australia.

#### COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One site comparison study in Brazil found that a reforested area had significantly lower bat diversity than a native forest fragment.

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, site comparison study in Australia found that forests restored after mining had significantly higher or similar bat activity (relative abundance) as unmined forests for five of seven bat species.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 40%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/2050

#### **Restore or create grassland**

One study evaluated the effects of creating grassland on bat populations. The study was in the UK.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between speciesrich grassland created on agri-environment scheme farms and improved pasture or crop fields on conventional farms.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 2%; certainty 10%; harms 0%).* http://www.conservationevidence.com/actions/2051

#### **No evidence found (no assessment)**


## 2.13.1 Species management


## **Likely to be beneficial**

### **Provide bat boxes for roosting bats**

Thirty-nine studies evaluated the effects of providing bat boxes for roosting bats on bat populations. Twenty-five studies were in Europe, eight studies were in North America, three studies were in Australia, two studies were in South America, and one study was a worldwide review.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

#### USAGE (39 STUDIES)

Uptake (9 studies): Nine replicated studies in Europe and the USA found that the number of bats using bat boxes increased by 2–10 times up to 10 years after installation.

Use (39 studies): Thirty-six of thirty-eight studies (including thirty-one replicated studies and one review) in Europe, the USA, South America, and Australia found that bats used bat boxes installed under bridges and in forest or woodland, forestry plantations, farmland, pasture, wetlands, urban areas or unknown habitats. The other two studies in the USA and UK found that bats displaced from buildings did not use any of 43 bat houses of four different designs or 12 heated bat boxes of one design. One review of 109 studies across Europe, North America and Asia found that 72 bat species used bat boxes, although only 18 species commonly used them, and 31 species used them as maternity roosts. Twenty studies (including sixteen replicated studies, one before-and-after study and one review) found bats occupying less than half of bat boxes provided (0– 49%). Nine replicated studies found bats occupying more than half of bat boxes provided (54–100%).

#### OTHER (19 STUDIES)

Bat box design (14 studies): Two studies in Germany and Portugal found that bats used black bat boxes more than grey or white boxes. One of two studies in Spain and the USA found higher occupancy rates in larger bat boxes. One study in the USA found that bats used both resin and wood cylindrical bat boxes, but another study in the USA found that resin bat boxes became occupied more quickly than wood boxes. One study in the UK found higher occupancy rates in concrete than wooden bat boxes. One study in Spain found that more bats occupied bat boxes that had two compartments than one compartment in the breeding season. One study in Lithuania found that bat breeding colonies occupied standard and four/five chamber bat boxes and individuals occupied flat bat boxes. Three studies in the USA, UK and Spain found bats selecting four of nine, three of five and three of four bat box designs. One study in the UK found that different bat box designs were used by different species. One study in Costa Rica found that bat boxes simulating tree trunks were used by 100% of bats and in group sizes similar to natural roosts.

Bat box position (10 studies): Three studies in Germany, Spain and the USA found that bat box orientation and/or the amount of exposure to sunlight affected bat occupancy, and one study in Spain found that orientation did not have a significant effect on occupancy. Two studies in the UK and Italy found that bat box height affected occupancy, and two studies in Spain and the USA found no effect of height. Two studies in the USA and Spain found higher occupancy of bat boxes on buildings than on trees. One study in Australia found that bat boxes were occupied more often in farm forestry sites than in native forest, one study in Poland found higher occupancy in pine relative to mixed deciduous stands, and one study in Costa Rica found higher occupancy in forest fragments than in pasture. One study in the USA found higher occupancy rates in areas where bats were known to roost prior to installing bat boxes.

*Assessment: likely to be beneficial (effectiveness 50%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/1024

### **Unknown effectiveness (limited evidence)**

### **Manage microclimate of artificial bat roosts**

Three studies evaluated the effects of managing the microclimate of artificial bat roosts on bat populations. Two studies were in the UK and one in Spain.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in Spain found more bats in two artificial roosts within buildings after they had been modified to reduce internal roost temperatures.

#### USAGE (2 STUDIES)

Use (2 studies): One replicated, before-and-after study in the UK found that heated bat boxes were used by common pipistrelle bats at one of seven sites, but none were used by maternity colonies. One replicated study in the UK found that none of the 12 heated bat boxes installed within churches were used by displaced Natterer's bats.

*Assessment: unknown effectiveness (effectiveness 40%; certainty 30%; harms 0%).*

## **Rehabilitate injured/orphaned bats to maintain wild bat populations**

Four studies evaluated the effects of rehabilitating injured/orphaned bats on bat populations. One study was in Brazil, two studies were in the UK, and one in Italy.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (4 STUDIES)

Survival (4 studies): One study in Brazil found that two hand-reared orphaned greater spear-nosed bats survived for over three months in captivity. Two studies in the UK and Italy found that 70–90% of handreared pipistrelle bats survived for at least 4–14 days after release into the wild, and six of 21 bats joined wild bat colonies. One study in the UK found that pipistrelle bats that flew in a large flight cage for long periods before release survived for longer and were more active than bats that flew for short periods or in a small enclosure. One study in the UK found that 13% of ringed hand-reared pipstrelle bats were found alive in bat boxes 38 days to almost four years after release into the wild.

Condition (1 study): One study in Brazil found that two orphaned greater spear-nosed bats increased in body weight and size after being handreared, and reached a normal size for the species after 60 days.

#### USAGE (0 STUDIES)

*Assessment: unknown effectiveness (effectiveness 47%; certainty 27%; harms 0%).*

http://www.conservationevidence.com/actions/2054

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Legally protect bat species

## 2.13.2 *Ex-situ* conservation


## **Unlikely to be beneficial**

#### **Breed bats in captivity**

Six studies evaluated the effects of breeding bats in captivity on bat populations. Three studies were in the USA, two in the UK and one in Brazil.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (6 STUDIES)

Reproductive success (5 studies): Five studies in the USA, UK and Brazil found that 6–100% of female bats captured in the wild successfully conceived, gave birth and reared young in captivity. Two studies in the UK and Brazil found that two of five and two of three bats born in captivity successfully gave birth to live young.

Survival (6 studies): Six studies in the USA, UK and Brazil found that 20–86% of bat pups born in captivity survived from between 10 days to adulthood.

#### USAGE (0 STUDIES)

*Assessment: unlikely to be beneficial (effectiveness 30%; certainty 40%; harms 18%).*

http://www.conservationevidence.com/actions/2053

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Release captive-bred bats

## 2.13.3 Translocation

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for bat translocation? Likely to be ineffective**  ● Translocate bats

**or harmful**

## **Likely to be ineffective or harmful**

### **Translocate bats**

Two studies evaluated the effects of translocating bats on bat populations. One study was in New Zealand and one study was in Switzerland.

#### COMMUNITY RESPONSE (0 STUDIES)

#### POPULATION RESPONSE (2 STUDIES)

Reproductive success (1 study): One study in Switzerland found that a female greater horseshoe bat that settled at a release site after translocation had a failed pregnancy.

Survival (1 study): One study in Switzerland found that four of 18 bats died after translocation.

Condition (1 study): One study in New Zealand found that lesser shorttailed bats captured at release sites eight months after translocation were balding and had damaged, infected ears.

#### USAGE (2 STUDIES)

Uptake (2 studies): Two studies in New Zealand and Switzerland found that low numbers of bats remained at release sites after translocation.

Behaviour change (1 study): One study in Switzerland found that bats homed after release at translocation sites less than 20 km from their original roosts.

*Assessment: likely to be ineffective or harmful (effectiveness 5%; certainty 40%; harms 80%).*

# 2.14 Education and awareness raising


#### **No evidence found (no assessment)**


# 3. BIRD CONSERVATION

**David R. Williams, Matthew F. Child, Lynn V. Dicks, Nancy Ockendon, Robert G. Pople, David A. Showler, Jessica C. Walsh, Erasmus K. H. J. zu Ermgassen & William J. Sutherland**

#### **Expert assessors**

**Tatsuya Amano**, University of Cambridge, UK **Andy Brown**, Natural England, UK **Fiona Burns**, Royal Society for the Protection of Birds, UK **Yohay Carmel**, Israel Institute of Technology **Mick Clout**, University of Auckland, New Zealand **Geoff Hilton**, Wildfowl & Wetlands Trust, UK **Nancy Ockendon**, University of Cambridge, UK **James Pearce-Higgins**, British Trust for Ornithology, UK **Sugoto Roy**, Food and Environment Research Agency, DEFRA, UK **Rebecca K. Smith**, University of Cambridge, UK **William J. Sutherland**, University of Cambridge, UK **Judit Szabo**, Charles Darwin University, Australia **Bernie Tershy**, University of California, USA **Des Thomson**, Scottish Natural Heritage, UK **Stuart Warrington**, National Trust, UK **David Williams**, University of Cambridge, UK

**Scope of assessment**: for native wild bird species across the world.

**Assessed:** 2015.

**Effectiveness measure** is the median % score.

**Certainty measure** is the median % certainty of evidence, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects to the group of species of concern. This was not scored for section 3.11 on invasive species.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 3.1 Habitat protection


### **Likely to be beneficial**

### **Legally protect habitats for birds**

Four studies from Europe found that populations increased after habitat protection and a review from China found high use of protected habitats by cranes. A replicated, randomised and controlled study from Argentina found that some, but not all bird groups had higher species richness or were at higher densities in protected habitats. *Assessment: likely to be beneficial (effectiveness 50%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/158

#### **Trade-off between benefit and harms**

#### **Provide or retain un-harvested buffer strips**

Three replicated studies from the USA found that species richness or abundances were higher in narrow (<100 m) strips of forest, but five

#### *Bird Conservation*

replicated studies from North America found that wider strips retained a community more similar to that of uncut forest than narrow strips. Tw replicated studies from the USA found no differences in productivity between wide and narrow buffers, but that predation of artificial nests was higher in buffers than in continuous forest. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 55%; harms 20%).*

http://www.conservationevidence.com/actions/161

## **Unknown effectiveness (limited evidence)**

#### **Ensure connectivity between habitat patches**

Two studies of a replicated, controlled experiment in Canadian forests found that some species (not forest specialists) were found at higher densities in forest patches connected to continuous forest, compared to isolated patches and that some species used corridors more than clearcuts between patches. *Assessment: unknown effectiveness — limited evidence (effectiveness 38%; certainty 38%; harms 0%).*

# 3.2 Education and awareness raising


### **Likely to be beneficial**

#### **Raise awareness amongst the general public through campaigns and public information**

A literature review from North America found that education was not sufficient to change behaviour, but that it was necessary for the success of economic incentives and law enforcement. *Assessment: likely to be beneficial (effectiveness 45%; certainty 48%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Provide bird feeding materials to families with young children**

A single replicated, paired study from the USA found that most children involved in a programme providing families with bird food increased their knowledge of birds, but did not significantly change their environmental attitudes. *Assessment: unknown effectiveness — limited evidence (effectiveness 42%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/163

#### **No evidence found (no assessment)**


# 3.3 Threat: Residential and commercial development


#### **Unknown effectiveness (limited evidence)**

#### **Angle windows to reduce bird collisions**

A single randomised, replicated and controlled experiment in the USA found that fewer birds collided with windows angled away from the vertical. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/166

#### **Mark windows to reduce bird collisions**

Two randomised, replicated and controlled studies found that marking windows did not appear to reduce bird collisions. However, when windows were largely covered with white cloth, or tinted, fewer birds flew towards or collided with them. A third randomised, replicated and controlled study found that fewer birds collided with tinted windows than with un-tinted ones, although the authors noted that the poor reflective quality of the glass could have influenced the results. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 20%; harms 0%).*

# 3.4 Threat: Agriculture

## 3.4.1 All farming systems


#### *Bird Conservation*


## **Beneficial**

## **Plant wild bird seed or cover mixture**

Seven of 41 studies found that fields or farms with wild bird cover had higher diversity than other sites, or that wild bird cover held more species than other habitats. Thirty-two studies found that populations, or abundances of some or all species were higher on wild bird cover than other habitats, or that wild bird cover was used more than other habitats. Four of these studies investigated several interventions at once. Thirteen studies found that bird populations or densities were similar on wild bird cover and other habitats that some species were not associated with wild bird cover, or that birds rarely used wild bird cover. Three studies found higher productivities of birds on wild bird cover than other habitats. Two found no differences for some or all species studied. Two studies found that survival of grey partridge or artificial nests increased on wild bird cover; one found lower partridge survival in farms with wild bird cover than other farms. Five studies from the UK found that some wild bird cover crops were used more than others. A study and a review found that the arrangement of wild bird cover in the landscape affected its use by birds. *Assessment: beneficial (effectiveness 81%; certainty 81%; harms 0%).*

#### **Provide (or retain) set-aside areas in farmland**

Four out of 23 studies from Europe and North America found more species on set-aside than on crops. One study found fewer. Twenty-one studies found that some species were at higher densities on set-aside than other habitats, or that they used set-aside more often. Four found that some species were found at lower densities on set-aside than other habitats. Three studies found that waders and Eurasian skylarks had higher productivities on set-aside than other crops. One study found that skylarks on set-aside had lower similar or lower productivities than on crops. One study from the UK found that rotational set-aside was used more than non-rotational set-aside, another found no difference. A review from North America and Europe found that naturally regenerated set-aside held more birds and more species than sown set-aside. *Assessment: beneficial (effectiveness 70%; certainty 75%; harms 0%).*

http://www.conservationevidence.com/actions/175

#### **Likely to be beneficial**

#### **Create uncultivated margins around intensive arable or pasture fields**

One of eight studies found that three sparrow species found on uncultivated margins on a site in the USA were not found on mown field edges. A replicated study from Canada found fewer species in uncultivated margins than in hedges or trees. Three studies found that some bird species were associated with uncultivated margins, or that birds were more abundant on margins than other habitats. One study found that these effects were very weak and four studies of three experiments found that uncultivated margins contained similar numbers of birds as other habitats in winter, or that several species studied did not show associations with margins. A study from the UK found that yellowhammers used uncultivated margins more than crops in early summer. Use fell in uncut margins later in the year. A study from the UK found that grey partridge released on uncultivated margins had high survival. *Assessment: likely to be beneficial (effectiveness 45%; certainty 55%; harms 0%).*

## **Increase the proportion of natural/semi-natural habitat in the farmed landscape**

Two studies from Switzerland and Australia, of the five we captured, found that areas with plantings of native species, or areas under a scheme designed to increase semi-natural habitats (the Swiss Ecological Compensation Areas scheme), held more bird species than other areas. One study from Switzerland found that populations of three bird species increased in areas under the Ecological Compensation Areas scheme. A third Swiss study found that some habitats near Ecological Compensation Areas held more birds than habitats further away, but the overall amount of Ecological Compensation Area had no effect on bird populations. A study from the UK found no effect of habitat-creation on grey partridge populations. *Assessment: likely to be beneficial (effectiveness 45%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/171

## **Manage ditches to benefit wildlife**

One study of four from the UK found that bunded ditches were visited more often by birds than non-bunded ditches. Three studies found that some birds responded positively to ditches managed for wildlife, but that other species did not respond to management, or responded negatively. *Assessment: likely to be beneficial (effectiveness 40%; certainty 49%; harms 14%).*

http://www.conservationevidence.com/actions/180

#### **Pay farmers to cover the costs of conservation measures**

Three out of 31 studies found national population increases in three species after payment schemes targeted at their conservation. One found that many other species continued declining. Twenty-two studies found that at least some species were found at higher densities on sites with agri-environment schemes; some differences were present only in summer or only in winter. Fifteen studies found some species at similar densities on agri-environment schemes and non-agri-environment scheme sites or appeared to respond negatively to agri-environment schemes. One study found that grey partridge survival was higher in some years on agri-environment scheme sites. Two studies found higher productivity on agri-environment scheme sites for some species, one found no effect of agri-environment schemes. A review found that some agri-environment schemes options were not being used enough to benefit many species of bird. A study from the UK found that there was no difference in the densities of seed-eating birds in winter between two agri-environment scheme designations. *Assessment: likely to be beneficial (effectiveness 56%; certainty 80%; harms 0%).*

http://www.conservationevidence.com/actions/172

## **Plant grass buffer strips/margins around arable or pasture fields**

One of 15 studies found more bird species in fields in the USA that were bordered by grass margins than in unbordered fields. Two studies from the UK found no effect of margins on species richness. One study found that more birds used grass strips in fields than used crops. Even more used grass margins. Nine studies from the USA and UK found that sites with grass margins had more positive population trends or higher populations for some birds, or that some species showed strong habitat associations with grass margins. Three studies found no such effect for some or all species. Two studies found that species used margins more than other habitats and one found that birds used cut margins more than uncut during winter, but less than other habitats during summer. A study from the UK found that grey partridge broods were smaller on grass margins than other habitat types. *Assessment: likely to be beneficial (effectiveness 47%; certainty 54%; harms 0%).*

http://www.conservationevidence.com/actions/191

### **Plant nectar flower mixture/wildflower strips**

Three of seven studies found that birds used wildflower strips more than other habitats; two found strips were not used more than other habitats. A study from Switzerland found that Eurasian skylarks were more likely to nest in patches sown with annual weeds than in crops and were less likely to abandon nests. A study from the UK found that management of field margins affected their use more than the seed mix used. *Assessment: likely to be beneficial (effectiveness 55%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/189

## **Leave refuges in fields during harvest**

One study found that fewer gamebirds came into contact with mowing machinery when refuges were left in fields. A study from the UK found that Eurasian skylarks did not nest at higher densities in uncut refuges than in the rest of the field. *Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 0%).*

http://www.conservationevidence.com/actions/193

## **Reduce conflict by deterring birds from taking crops (using bird scarers)**

A controlled paired study in the USA found reduced levels of damage to almond orchards when American crow distress calls were broadcast. A study in Pakistan found that four pest species were less abundant when reflector ribbons were hung above crops compared to where ribbons were not used. *Assessment: likely to be beneficial (effectiveness 66%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/199

#### **Relocate nests at harvest time to reduce nestling mortality**

A study from Spain found that Montagu's harrier clutches had higher hatching and fledging rates when they were temporarily moved during harvest than control nests that were not moved. *Assessment: likely to be beneficial (effectiveness 55%; certainty 42%; harms 0%).*

http://www.conservationevidence.com/actions/195

#### **Use mowing techniques to reduce mortality**

One of three studies from the UK found a large increase in the national population of corncrakes after a scheme to delay mowing and promote corncrake-friendly mowing techniques. Two studies found lower levels of corncrake and Eurasian skylark mortality when wildlife-friendly mowing techniques were used. *Assessment: likely to be beneficial (effectiveness 85%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/192

#### **Unknown effectiveness (limited evidence)**

#### **Control scrub on farmland**

A study from the UK found farms with a combined intervention that included scrub control had lower numbers of young grey partridge per adult. *Assessment: unknown effectiveness — limited evidence (effectiveness 7%; certainty 9%; harms 1%).*

http://www.conservationevidence.com/actions/197

## **Offer per clutch payment for farmland birds**

One of two studies from the Netherlands found slightly higher breeding densities of waders on farms with per clutch payment schemes but this and another study found no higher numbers overall. One study found higher hatching success on farms with payment schemes. *Assessment: unknown effectiveness — limited evidence (effectiveness 43%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/196

## **Manage hedges to benefit wildlife**

One of seven studies found no differences in the number of species in a UK site with wildlife-friendly hedge management and sites without. Seven studies found that some species increased in managed hedges or were more likely to be found in them than other habitats. One investigated several interventions at the same time. Four studies found that some species responded negatively or not at all to hedge management or that effects varied across regions of the UK. *Assessment: unknown effectiveness — limited evidence (effectiveness 39%; certainty 38%; harms 3%).*

http://www.conservationevidence.com/actions/177

#### **Plant new hedges**

A study from the USA found that populations of northern bobwhites increased following several interventions including the planting of new hedges. *Assessment: unknown effectiveness — limited evidence (effectiveness 23%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/178

## **Reduce conflict by deterring birds from taking crops (using repellents)**

A replicated, randomised and controlled *ex situ* study in the USA found that dickcissels consumed less rice if it was treated with two repellents compared to controls. *Assessment: unknown effectiveness — limited evidence (effectiveness 29%; certainty 27%; harms 0%).*

#### **Take field corners out of management**

A study from the UK found that overwinter survival of grey partridge was positively correlated with taking field corners out of management, but this relationship was only significant in one of three winters. There was no relationship with measures of productivity (brood size, young: adult). *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/198

#### **Likely to be ineffective or harmful**

#### **Mark bird nests during harvest or mowing**

A study from the Netherlands found that fewer northern lapwing nests were destroyed when they were marked with bamboo poles than when they were unmarked. *Assessment: likely to be ineffective or harmful (effectiveness 30%; certainty 45%; harms 20%).*

http://www.conservationevidence.com/actions/148

#### **No evidence found (no assessment)**


## 3.4.2 Arable farming


#### **Likely to be beneficial**

### **Create 'skylark plots' (undrilled patches in cereal fields)**

One study of seven found that the Eurasian skylark population on a farm increased after skylark plots were provided. Another found higher skylark densities on fields with plots in. Two studies from the UK found that skylark productivity was higher for birds with skylark plots in their territories, a study from Switzerland found no differences. Two studies from Denmark and Switzerland found that skylarks used plots more than expected, but a study from the UK found that seed-eating songbirds did not. *Assessment: likely to be beneficial (effectiveness 65%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/214

## **Leave overwinter stubbles**

Three of fourteen studies report positive population-level changes in two species after winter stubble provision. All investigated several interventions at once. Eight studies found that some farmland birds were found on stubbles or were positively associated with them, three investigated several interventions and one found no more positive associations than expected by chance. A study from the UK found that most species did not preferentially use stubble, compared to cover crops and another found that a greater area of stubble in a site meant lower grey partridge brood size. Five studies from the UK found that management of stubbles influenced their use by birds. One study found that only one species was more common on stubbles under agri-environment schemes. *Assessment: likely to be beneficial (effectiveness 40%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/203

## **Leave uncropped cultivated margins or fallow land (includes lapwing and stone curlew plots)**

Three of nine studies report that the UK population of Eurasian thickknees increased following a scheme to promote lapwing plots (and other interventions). A study from the UK found that plots did not appear to influence grey partridge populations. Four studies from the UK found that at least one species was associated with lapwing plots, or used them for foraging or nesting. One study found that 11 species were not associated with plots, another that fewer used plots than used crops in two regions of the UK. Two studies found that nesting success was higher on lapwing plots and fallow than in crops. A third found fewer grey partridge chicks per adult on sites with lots of lapwing plots. *Assessment: likely to be beneficial (effectiveness 59%; certainty 55%; harms 15%).*

#### **Sow crops in spring rather than autumn**

One study from Sweden, of three examining the effects of spring-sown crops, found that more birds were found on areas with spring, rather than autumn-sown crops. A study from the UK found that several species used the study site for the first time after spring-sowing was started. All three studies found that some populations increased after the start of spring sowing. A study from the UK found that some species declined as well. A study from Sweden found that hatching success of songbirds and northern lapwing was lower on spring-sown, compared with autumn-sown crops. *Assessment: likely to be beneficial (effectiveness 55%; certainty 67%; harms 10%).*

http://www.conservationevidence.com/actions/207

#### **Undersow spring cereals, with clover for example**

Four of five studies from the UK found that bird densities were higher on undersown fields or margins than other fields, or that use of fields increased if they were undersown. Two studies of the same experiment found that not all species nested at higher densities in undersown habitats. A study from the UK found that grey partridge populations were lower on sites with large amounts of undersown cereal. *Assessment: likely to be beneficial (effectiveness 60%; certainty 45%; harms 10%).*

http://www.conservationevidence.com/actions/208

#### **Trade-off between benefit and harms**

#### **Reduce tillage**

Six of ten studies found that some or all bird groups had higher species richness or diversity on reduced-tillage fields, compared to conventional fields in some areas. Two studies found that some groups had lower diversity on reduced-tillage sites, or that there was no difference between treatments. Nine studies found that some species were found at higher densities on reduced tillage fields, six found that some species were at similar or lower densities. Three studies found evidence for higher productivities on reduced-tillage fields. One found that not all measures of productivity were higher. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 48%; harms 51%).*

#### **Unknown effectiveness (limited evidence)**

#### **Implement mosaic management**

One of two studies from the Netherlands found that northern lapwing population trends, but not those of three other waders, became more positive following the introduction of mosaic management. The other found that black-tailed godwit productivity was higher under mosaic management than other management types. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 33%; harms 0%).*

http://www.conservationevidence.com/actions/130

#### **Increase crop diversity to benefit birds**

A study from the UK found that more barnacle geese used a site after the amount of land under cereals was decreased and several other interventions were used. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/201

#### **Plant more than one crop per field (intercropping)**

A study from the USA found that 35 species of bird used fields with intercropping, with four nesting, but that productivity from the fields was very low. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 36%; harms 18%).*

http://www.conservationevidence.com/actions/209

#### **Unlikely to be beneficial**

#### **Create beetle banks**

Two of six studies from the UK found that some bird populations were higher on sites with beetle banks. Both investigated several interventions at once. Two studies found no relationships between bird species abundances or populations and beetle banks. Two studies (including a review) from the

*Agriculture*

UK found that three bird species used beetle banks more than expected, one used them less than expected. *Assessment: unlikely to be beneficial (effectiveness 30%; certainty 41%; harms 0%).*

http://www.conservationevidence.com/actions/217

#### **Likely to be ineffective or harmful**

#### **Plant cereals in wide-spaced rows**

One of three studies from the UK found that fields with wide-spaced rows held more Eurasian skylark nests than control fields. One study found that fields with wide-spaced rows held fewer nests. Both found that fields with wide-spaced rows held fewer nests than fields with skylark plots. A study from the UK found that skylark chicks in fields with wide-spaced rows had similar diets to those in control fields. *Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 44%; harms 20%).*

http://www.conservationevidence.com/actions/216

#### **Revert arable land to permanent grassland**

All five studies looking at the effects of reverting arable land to grassland found no clear benefit to birds. The studies monitored birds in winter or grey partridges in the UK and wading birds in Denmark. They included three replicated controlled trials. *Assessment: likely to be ineffective or harmful (effectiveness 0%; certainty 64%; harms 10%).*

http://www.conservationevidence.com/actions/210

#### **No evidence found (no assessment)**


## 3.4.3 Livestock farming


## **Likely to be beneficial**

## **Delay mowing date on grasslands**

Two of five studies (both reviews) found that the UK corncrake populations increased following two schemes to encourage farmers to delay mowing. A study from the Netherlands found no evidence that waders and other birds were more abundant in fields with delayed mowing. Another study from the Netherlands found that fields with delayed mowing held more birds than other fields, but differences were present before the scheme began and population trends did not differ between treatments. A study from the USA found that fewer nests were destroyed by machinery in late-cut fields, compared with early-cut fields. *Assessment: likely to be beneficial (effectiveness 45%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/223

#### **Leave uncut rye grass in silage fields**

All four studies from the UK (including two reviews) found that seed-eating birds were benefited by leaving uncut (or once-cut) rye grass in fields, or that seed-eating species were more abundant on uncut plots. Three studies found that seed-eating birds were more abundant on uncut and ungrazed plots than on uncut and grazed plots. A study from the UK found that the responses of non-seed-eating birds were less certain than seed-eating species, with some species avoiding uncut rye grass. *Assessment: likely to be beneficial (effectiveness 67%; certainty 56%; harms 8%).*

http://www.conservationevidence.com/actions/224

## **Maintain species-rich, semi-natural grassland**

One of two studies found that the populations of five species increased in an area of the UK after the start of management designed to maintain unimproved grasslands. A study from Switzerland found that wetland birds nested at greater densities on managed hay meadows than expected, but birds of open farmland used hay meadows less. *Assessment: likely to be beneficial (effectiveness 41%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/218

#### **Maintain traditional water meadows**

One of four studies (from the UK) found that the populations of two waders increased on reserves managed as water meadows. Two studies from the Netherlands found that there were more waders or birds overall on specially managed meadows or 12.5 ha plots, but one found that these differences were present before management began, the other found no differences between individual fields under different management. Two studies from the UK and Netherlands found that wader populations were

#### *Bird Conservation*

no different between specially and conventionally managed meadows, or that wader populations decreased on specially-managed meadows. A study from the UK found that northern lapwing productivity was not high enough to maintain populations on three of four sites managed for waders. *Assessment: likely to be beneficial (effectiveness 50%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/229

#### **Mark fencing to avoid bird mortality**

A study from the UK found that fewer birds collided with marked sections of deer fences, compared to unmarked sections. *Assessment: likely to be beneficial (effectiveness 65%; certainty 46%; harms 0%).*

http://www.conservationevidence.com/actions/238

#### **Plant cereals for whole crop silage**

Three studies of one experiment found that seed-eating birds used cerealbased wholecrop silage crops more than other crops in summer and winter. Insect-eating species used other crops and grassland more often. *Assessment: likely to be beneficial (effectiveness 55%; certainty 43%; harms 0%).*

http://www.conservationevidence.com/actions/225

#### **Reduce grazing intensity**

Nine of eleven studies from the UK and USA found that the populations of some species were higher on fields with reduced grazing intensity, compared to conventionally-grazed fields, or found that birds used these fields more. Three studies investigated several interventions at once. Five studies from Europe found that some or all species were no more numerous, or were less abundant on fields with reduced grazing. A study from the UK found that black grouse populations increased at reduced grazing sites (whilst they declined elsewhere). However, large areas with reduced grazing had low female densities. A study from the USA found that the number of species on plots with reduced grazing increased over time. A study from four European countries found no differences in the number of species on sites with low- or high-intensity grazing. *Assessment: likely to be beneficial (effectiveness 46%; certainty 55%; harms 0%).*

*Agriculture*

#### **Reduce management intensity of permanent grasslands**

Seven of eight European studies found that some or all birds studied were more abundant on grasslands with reduced management intensity, or used them more than other habitats for foraging. Five studies of four experiments found that some or all species were found at lower or similar abundances on reduced-management grasslands, compared to intensively-managed grasslands. *Assessment: likely to be beneficial (effectiveness 65%; certainty 46%; harms 0%).*

http://www.conservationevidence.com/actions/219

#### **Trade-off between benefit and harms**

#### **Exclude livestock from semi-natural habitat**

Two studies from the USA, out of 11 overall, found higher species richness on sites with grazers excluded. A study from Argentina found lower species richness and one from the USA found no difference. Seven studies from the USA found that overall bird abundance, or the abundances of some species were higher in sites with grazers excluded. Seven studies from the USA and Argentina found that overall abundance or the abundance of some species were lower on sites without grazers, or did not differ. Three studies found that productivities were higher on sites with grazers excluded. In one, the difference was only found consistently in comparison with improved pastures, not unimproved. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 57%; harms 30%).*

http://www.conservationevidence.com/actions/236

#### **Unknown effectiveness (limited evidence)**

#### **Create open patches or strips in permanent grassland**

A study from the UK found that Eurasian skylarks used fields with open strips in, but that variations in skylark numbers were too great to draw conclusions from this finding. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 19%; harms 0%).*

## **Maintain upland heath/moor**

A study from the UK found that bird populations in one region were increasing with agri-environment guidelines on moor management. There were some problems with overgrazing, burning and scrub encroachment. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/230

#### **Protect nests from livestock to reduce trampling**

One of two studies found that a population of Chatham Island oystercatchers increased following several interventions including the erection of fencing around individual nests. A study from Sweden found that no southern dunlin nests were trampled when protected by cages; some unprotected nests were destroyed. *Assessment: unknown effectiveness — limited evidence (effectiveness 56%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/237

#### **Provide short grass for waders**

A study from the UK found that common starlings and northern lapwing spent more time foraging on areas with short swards, compared to longer swards. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 32%; harms 0%).*

http://www.conservationevidence.com/actions/221

#### **Raise mowing height on grasslands**

One of two studies from the UK found that no more foraging birds were attracted to plots with raised mowing heights, compared to plots with shorter grass. A review from the UK found that Eurasian skylarks had higher productivity on sites with raised mowing heights, but this increase was not enough to maintain local populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 36%; harms 0%).*

## **Unlikely to be beneficial**

## **Use traditional breeds of livestock**

A study from four countries in Europe found no differences in bird abundances in areas grazed with traditional or commercial breeds. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/233

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 3.4.4 Perennial, non-timber crops


### **Unknown effectiveness (limited evidence)**

### **Maintain traditional orchards**

Two site comparison studies from the UK and Switzerland found that traditional orchards offer little benefit to birds. In Switzerland only one breeding bird species was associated with traditional orchards. In the UK, the population density of cirl bunting was negatively related to the presence of orchards. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 24%; harms 0%).*

http://www.conservationevidence.com/actions/240

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Manage perennial bioenergy crops to benefit wildlife

# 3.4.5 Aquaculture


## **Likely to be beneficial**

## **Deter birds from landing on shellfish culture gear**

A study from Canada found that fewer birds landed on oyster cages fitted with spikes than control cages. The same study found that fewer birds landed on oyster bags suspended 6 cm, but not 3 cm, underwater, compared to bags on the surface. *Assessment for using spikes on oyster cages: likely to be beneficial (effectiveness 60%; certainty 43%; harms 0%). Assessment for suspending oyster bags under water: likely to be beneficial (effectiveness 55%; certainty 43%; harms 0%).*

> http://www.conservationevidence.com/actions/257 http://www.conservationevidence.com/actions/256

#### **Disturb birds at roosts**

One study from the USA found reduced fish predation after fish-eating birds were disturbed at roosts. Five studies from the USA and Israel found that birds foraged less near disturbed roosts, or left the area after being disturbed. One found the effects were only temporary. *Assessment: likely to be beneficial (effectiveness 67%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/245

#### **Provide refuges for fish within ponds**

A study from the UK found that cormorants caught fewer fish in a pond with fish refuges in, compared to a control pond. *Assessment: likely to be beneficial (effectiveness 65%; certainty 43%; harms 0%).*

http://www.conservationevidence.com/actions/253

### **Use electric fencing to exclude fish-eating birds**

Two before-and-after trials from the USA found lower use of fish ponds by herons after electric fencing was installed. *Assessment: likely to be beneficial (effectiveness 60%; certainty 49%; harms 0%).*

```
http://www.conservationevidence.com/actions/247
```
## **Use 'mussel socks' to prevent birds from attacking shellfish**

A study from Canada found that mussel socks with protective sleeves lost fewer medium-sized mussels (but not small or large mussels), compared to unprotected mussel socks. *Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 0%).*

http://www.conservationevidence.com/actions/250

### **Use netting to exclude fish-eating birds**

Two studies from Germany and the USA, and a review, found that netting over ponds reduced the loss of fish to predatory birds. Two studies from the USA and the Netherlands found that birds still landed on ponds with netting, but that they altered their behaviour, compared to open ponds. Two studies from Germany and Israel found that some birds became entangled in netting over ponds. *Assessment: likely to be beneficial (effectiveness 60%; certainty 59%; harms 15%).*

http://www.conservationevidence.com/actions/248

#### **Unknown effectiveness (limited evidence)**

#### **Increase water turbidity to reduce fish predation by birds**

An *ex situ* study from France found that egret foraging efficiency was reduced in more turbid water. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/252

#### **Translocate birds away from fish farms**

A study from the USA found that translocating birds appeared to reduce bird numbers at a fish farm. A study from Belgium found that it did not. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 33%; harms 0%).*

http://www.conservationevidence.com/actions/251

#### **Use in-water devices to reduce fish loss from ponds**

A study from the USA found that fewer cormorants used two ponds after underwater ropes were installed; a study from Australia found that no fewer cormorants used ponds with gill nets in. *Assessment: unknown effectiveness — limited evidence (effectiveness 34%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/254

## **Unlikely to be beneficial**

## **Disturb birds using foot patrols**

Two replicated studies from Belgium and Australia found that using foot patrols to disturb birds from fish farms did not reduce the number of birds present or fish consumption. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/249

#### **Spray water to deter birds from ponds**

A study from Sweden found that spraying water deterred birds from fish ponds, but that some birds became habituated to the spray. *Assessment: unlikely to be beneficial (effectiveness 31%; certainty 43%; harms 0%).*

http://www.conservationevidence.com/actions/255

#### **Likely to be ineffective or harmful**

#### **Scare birds from fish farms**

One study from Israel found a population increase in fish-eating birds after efforts to scare them from fish farms, possibly due to lower persecution. One of two studies found evidence for reduced loss of fish when birds were scared from farms. Two studies from Australia and Belgium found that disturbing birds using foot patrols was not effective. Ten of 11 studies from across the world found some effects for acoustic deterrents, five of seven found that visual deterrents were effective. In both cases some studies found that results were temporary, birds became habituated or that some deterrents were effective, whilst others were not. One study found that trained raptors were effective, one found little evidence for the effectiveness of helicopters or light aircraft. *Assessment: likely to be ineffective or harmful (effectiveness 36%; certainty 64%; harms 0%).*

# 3.5 Threat: Energy production and mining


### **Unknown effectiveness (limited evidence)**

### **Paint wind turbines to increase their visibility**

A single, controlled *ex situ* experiment found that thick black stripes running across a wind turbine's blades made them more conspicuous to an American kestrel *Falco sparverius* than control (unpatterned) blades. Other designs were less visible or indistinguishable from controls. *Assessment: unknown effectiveness — limited evidence (effectiveness 16%; certainty 10%; harms 0%).*

# 3.6 Threat: Transportation and service corridors

## 3.6.1 Verges and airports


## **Likely to be beneficial**

## **Scare or otherwise deter birds from airports**

Two replicated studies in the UK and USA found that fewer birds used areas of long grass at airports, but no data were provided on the effect of long grass on strike rates or bird mortality. *Assessment: likely to be beneficial (effectiveness 50%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/261

## **Unknown effectiveness (limited evidence)**

## **Mow roadside verges**

A single replicated, controlled trial in the USA found that mowed roadside verges were less attractive to ducks as nesting sites, but had higher nesting success after four years. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 30%; harms 9%).*

http://www.conservationevidence.com/actions/259

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Sow roadside verges

## 3.6.2 Power lines and electricity pylons

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for power lines and electricity pylons?**


### **Beneficial**

### **Mark power lines**

A total of eight studies and two literature reviews from across the world found that marking power lines led to significant reductions in bird collision mortalities. Different markers had different impacts. *Assessment: beneficial (effectiveness 81%; certainty 85%; harms 0%).*

#### **Likely to be beneficial**

#### **Bury or isolate power lines**

A single before-and-after study in Spain found a dramatic increase in juvenile eagle survival following the burial or isolation of dangerous power lines. *Assessment: likely to be beneficial (effectiveness 60%; certainty 44%; harms 0%).*

http://www.conservationevidence.com/actions/262

#### **Insulate electricity pylons**

A single before-and-after study in the USA found that insulating power pylons significantly reduced the number of Harris's hawks electrocuted. *Assessment: likely to be beneficial (effectiveness 60%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/268

#### **Remove earth wires from power lines**

Two before-and-after studies from Norway and the USA describe significant reductions in bird collision mortalities after earth wires were removed from sections of power lines. *Assessment: likely to be beneficial (effectiveness 90%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/263

#### **Use perch-deterrents to stop raptors perching on pylons**

A single controlled study in the USA found that significantly fewer raptors were found near perch-deterrent lines, compared to controls, but no information on electrocutions was provided. *Assessment: likely to be beneficial (effectiveness 50%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/269

#### **Unknown effectiveness (limited evidence)**

#### **Thicken earth wires**

A single paired sites trial in the USA found no reduction in crane species collision rates in a wire span with an earth wire three times thicker than normal. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/264

## **Unlikely to be beneficial**

### **Add perches to electricity pylons**

A single before-and-after study in Spain found that adding perches to electricity pylons did not reduce electrocutions of Spanish imperial eagles. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 42%; harms 0%).*

http://www.conservationevidence.com/actions/267

## **Reduce electrocutions by using plastic, not metal, leg rings to mark birds**

A single replicated and controlled study in the USA found no evidence that using plastic leg rings resulted in fewer raptors being electrocuted. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 42%; harms 0%).*

http://www.conservationevidence.com/actions/270

### **Use raptor models to deter birds from power lines**

A single paired sites trial in Spain found that installing raptor models near power lines had no impact on bird collision mortalities. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 43%; harms 0%)*

# 3.7 Threat: Biological resource use

# 3.7.1 Reducing exploitation and conflict


## **Scare fish-eating birds from areas to reduce conflict**

Studies investigating scaring fish from fishing areas are discussed in 'Threat: Agriculture — Aquaculture'.

#### **Beneficial**

### **Use legislative regulation to protect wild populations**

Five out of six studies from Europe, Asia, North America and across the world, found evidence that stricter legislative protection was correlated with increased survival, lower harvests or increased populations. The sixth, a before-and-after study from Australia, found that legislative protection did not reduce harvest rates. *Assessment: beneficial (effectiveness 65%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/271

#### **Likely to be beneficial**

#### **Use wildlife refuges to reduce hunting disturbance**

Three studies from the USA and Europe found that more birds used refuges where hunting was not allowed, compared to areas with hunting, and more used the refuges during the open season. However, no studies examined the population-level effects of refuges. *Assessment: likely to be beneficial (effectiveness 45%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/278

#### **Unknown effectiveness (limited evidence)**

#### **Employ local people as 'biomonitors'**

A single replicated study in Venezuela found that poaching of parrot nestlings was significantly lower in years following the employment of five local people as 'biomonitors'. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/275

### **Increase 'on-the-ground' protection to reduce unsustainable levels of exploitation**

Two before-and-after studies from Europe and Central America found increases in bird populations and recruitment following stricter anti-poaching methods or the stationing of a warden on the island in question. However, the increases in Central America were only short-term, and were lost when the intensive effort was reduced. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/272

#### **Introduce voluntary 'maximum shoot distances'**

A single study from Denmark found a significant reduction in the injury rates of pink-footed geese following the implementation of a voluntary maximum shooting distance. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/279

#### **Mark eggs to reduce their appeal to collectors**

A single before-and-after study in Australia found increased fledging success of raptor eggs in a year they were marked with a permanent pen. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/276

#### **Move fish-eating birds to reduce conflict with fishermen**

A single before-and-after study in the USA found that Caspian tern chicks had a lower proportion of commercial fish in their diet following the movement of the colony away from an important fishery. *Assessment: unknown effectiveness — limited evidence (effectiveness 32%; certainty 24%; harms 0%).*

http://www.conservationevidence.com/actions/281

#### **Promote sustainable alternative livelihoods**

A single before-and-after study in Costa Rica found that a scarlet macaw population increased following several interventions including the promotion of sustainable, macaw-based livelihoods. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 19%; harms 0%).*

## **Provide 'sacrificial grasslands' to reduce conflict with farmers**

Two UK studies found that more geese used areas of grassland managed for them, but that this did not appear to attract geese from outside the study site and therefore was unlikely to reduce conflict with farmers. *Assessment: unknown effectiveness — limited evidence (effectiveness 18%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/280

#### **Relocate nestlings to reduce poaching**

A single replicated study in Venezuela found a significant reduction in poaching rates and an increase in fledging rates of yellow-shouldered amazons when nestlings were moved into police premises overnight. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/277

## **Use education programmes and local engagement to help reduce persecution or exploitation of species**

Six out of seven studies from across the world found increases in bird populations or decreases in mortality following education programmes, whilst one study from Venezuela found no evidence that poaching decreased following an educational programme. In all but one study reporting successes, other interventions were also used, and a literature review from the USA and Canada argues that education was not sufficient to change behaviour, although a Canadian study found that there was a significant shift in local peoples' attitudes to conservation and exploited species following educational programmes. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/274

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Use alerts during shoots to reduce mortality of non-target species

## 3.7.2 Reducing fisheries bycatch


#### *Bird Conservation*


### **Beneficial**

## **Use streamer lines to reduce seabird bycatch on longlines**

Ten studies from coastal and pelagic fisheries across the globe found strong evidence for reductions in bycatch when streamer lines were used. Five studies from the South Atlantic, New Zealand and Australia were inconclusive, uncontrolled or had weak evidence for reductions. One study from the sub-Antarctic Indian Ocean found no evidence for reductions. Three studies from around the world found that bycatch rates were lower when two streamers were used compared to one, and one study found rates were lower still with three streamers. *Assessment: beneficial (effectiveness 65%; certainty 75%; harms 0%).*

http://www.conservationevidence.com/actions/285

## **Likely to be beneficial**

## **Mark trawler warp cables to reduce seabird collisions**

A single replicated and controlled study in Argentina found lower seabird mortality (from colliding with warp cables) when warp cables were marked with orange traffic cones. *Assessment: likely to be beneficial (effectiveness 54%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/305

## **Reduce seabird bycatch by releasing offal overboard when setting longlines**

Two replicated and controlled studies in the South Atlantic and sub-Antarctic Indian Ocean found significantly lower seabird bycatch rates when offal was released overboard as lines were being set. *Assessment: likely to be beneficial (effectiveness 51%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/299

## **Weight baits or lines to reduce longline bycatch of seabirds**

Three replicated and controlled studies from the Pacific found lower bycatch rates of some seabird species on weighted longlines. An uncontrolled study found low bycatch rates with weighted lines but that weights only increased sink rates in small sections of the line. Some species were found to attack weighted lines more than control lines. *Assessment: likely to be beneficial (effectiveness 46%; certainty 45%; harms 15%).*

http://www.conservationevidence.com/actions/296

#### **Trade-off between benefit and harms**

#### **Set lines underwater to reduce seabird bycatch**

Five studies in Norway, South Africa and the North Pacific found lower seabird bycatch rates on longlines set underwater. However, results were species-specific, with shearwaters and possibly albatrosses continuing to take baits set underwater. *Assessment: trade-offs between benefits and harms (effectiveness 61%; certainty 50%; harms 24%).*

http://www.conservationevidence.com/actions/288

#### **Set longlines at night to reduce seabird bycatch**

Six out of eight studies from around the world found lower bycatch rates when longlines were set at night, but the remaining two found higher bycatch rates (of northern fulmar in the North Pacific and white-chinned petrels in the South Atlantic, respectively). Knowing whether bycatch species are night- or day-feeding is therefore important in reducing bycatch rates. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 70%; harms 48%).*

#### **Unknown effectiveness (limited evidence)**

#### **Dye baits to reduce seabird bycatch**

A single randomised, replicated and controlled trial in Hawaii, USA, found that albatrosses attacked baits at significantly lower rates when baits were dyed blue. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/293

#### **Thaw bait before setting lines to reduce seabird bycatch**

A study from Australia found that longlines set using thawed baits caught significantly fewer seabirds than controls. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/298

### **Turn deck lights off during night-time setting of longlines to reduce bycatch**

A single replicated and controlled study in the South Atlantic found lower seabird bycatch rates on night-set longlines when deck lights were turned off. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/284

#### **Use a sonic scarer when setting longlines to reduce seabird bycatch**

A single study from the South Atlantic found that seabirds only temporarily changed behaviour when a sonic scarer was used, and seabird bycatch rates did not appear to be lower on lines set with a scarer. *Assessment: unknown effectiveness — limited evidence (effectiveness 2%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/295

#### **Use acoustic alerts on gillnets to reduce seabird bycatch**

A randomised, replicated and controlled trial in a coastal fishery in the USA found that fewer guillemots (common murres) but not rhinoceros auklets were caught in gillnets fitted with sonic alerts. *Assessment: unknown effectiveness — limited evidence (effectiveness 44%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/301

#### **Use bait throwers to reduce seabird bycatch**

A single analysis found significantly lower seabird bycatch on Australian longliners when a bait thrower was used to set lines. *Assessment: unknown effectiveness — limited evidence (effectiveness 46%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/291

## **Use bird exclusion devices such as 'Brickle curtains' to reduce seabird mortality when hauling longlines**

A single replicated study found that Brickle curtains reduced the number of seabirds caught, when compared to an exclusion device using only a single boom. Using purse seine buoys as well as the curtain appeared to be even more effective, but sample sizes did not allow useful comparisons. *Assessment: unknown effectiveness — limited evidence (effectiveness 48%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/302

## **Use high visibility mesh on gillnets to reduce seabird bycatch**

A single randomised, replicated and controlled trial in a coastal fishery in the USA found that fewer guillemots (common murres) and rhinoceros auklets were caught in gillnets with higher percentages of brightly coloured netting. However, such netting also reduced the catch of the target salmon. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/303

#### **Use shark liver oil to deter birds when setting lines**

Two out of three replicated and controlled trials in New Zealand found that fewer birds followed boats or dived for baits when non-commercial shark oil was dripped off the back of the boat. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 25%; harms 0%).*

## **Likely to be ineffective or harmful**

## **Use a line shooter to reduce seabird bycatch**

Two randomised, replicated and controlled trials found that seabird bycatch rates were higher (in the North Pacific) or the same (in Norway) on longlines set using line shooters, compared to those set without a shooter. *Assessment: likely to be ineffective or harmful (effectiveness 0%; certainty 50%; harms 40%).*

http://www.conservationevidence.com/actions/290

#### **No evidence found (no assessment)**


# 3.8 Threat: Human intrusions and disturbance


#### **Likely to be beneficial**

#### **Provide paths to limit disturbance**

A study from the UK found that two waders nested closer to a path, or at higher densities near the path, following resurfacing, which resulted in far fewer people leaving the path. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

## **Start educational programmes for personal watercraft owners**

A before-and-after study in the USA found that common tern reproduction increased, and rates of disturbance decreased, following a series of educational programmes aimed at recreational boat users. *Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/314

## **Use signs and access restrictions to reduce disturbance at nest sites**

Six studies from across the world found increased numbers of breeders, higher reproductive success or lower levels of disturbance in waders and terns following the start of access restrictions or the erection of signs near nesting areas. Two studies from Europe and Antarctica found no effect of access restrictions on reproductive success in eagles and penguins, respectively. *Assessment: likely to be beneficial (effectiveness 59%; certainty 55%; harms 10%).*

http://www.conservationevidence.com/actions/309

## **Use voluntary agreements with local people to reduce disturbance**

A before-and-after trial in the USA found significantly lower rates of waterfowl disturbance following the establishment of a voluntary waterfowl avoidance area, despite an overall increase in boat traffic. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/313

### **Unknown effectiveness (limited evidence)**

#### **Habituate birds to human visitors**

A study from Australia found that bridled terns from heavily disturbed sites had similar or higher reproductive success compared with less-disturbed sites, possibly suggesting that habituation had occurred. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

## **Use nest covers to reduce the impact of research on predation of ground-nesting seabirds**

A before-and-after study from Canada found that hatching success of Caspian terns was significantly higher when researchers protected nests after disturbing adults from them. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 35%; harms 19%).*

http://www.conservationevidence.com/actions/316

## **No evidence found (no assessment)**


# 3.9 Threat: Natural system modifications



### **Likely to be beneficial**

#### **Create scrapes and pools in wetlands and wet grasslands**

Four out of six studies from the UK and North America found that more bird used sites, or breeding populations on sites increased, after ponds or scrapes were created. A study from the USA found that some duck species used newly created ponds and others used older ponds. A study from the UK found that northern lapwing chicks foraged in newly created features and that chick condition was higher in sites with a large number of footdrains. *Assessment: likely to be beneficial (effectiveness 75%; certainty 60%; harms 0%).*

http://www.conservationevidence.com/actions/359

## **Provide deadwood/snags in forests (use ring-barking, cutting or silvicides)**

One of five studies found that forest plots provided with snags had higher bird diversity and abundance than plots without snags. Three of four studies from the USA and UK found that species used artificially-created snags for nesting and foraging. One study from the USA found that use increased with how long a snag had been dead. *Assessment: likely to be beneficial (effectiveness 45%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/343

#### **Use patch retention harvesting instead of clearcutting**

One of two studies (from the USA) found that areas under patch retention harvesting contained more birds of more species than clearcut areas, retaining similar numbers to unharvested areas. Two studies found that forest specialist species were found more frequently in patch retention plots than under other management. Habitat generalists declined on patch retention sites compared to other managements. *Assessment: likely to be beneficial (effectiveness 70%; certainty 46%; harms 0%).*

### **Trade-off between benefit and harms**

### **Clear or open patches in forests**

Seven out of nine studies from the UK and USA found that earlysuccessional species increased in clearcut areas of forests, compared to other management. Two studies found that mature-forest species declined. One study found no differences in species richness between treatments, another found no consistent differences. A study from the USA found that a mosaic of cut and uncut areas supported a variety of species. *Assessment: trade-offs between benefits and harms (effectiveness 55%; certainty 60%; harms 30%).*

http://www.conservationevidence.com/actions/326

#### **Employ grazing in artificial grasslands/pastures**

Five studies from the UK and USA found use or nesting densities were higher in grazed compared to ungrazed areas. A study from Canada found an increase in duck populations following the start of grazing along with other interventions. Eight studies from the UK, Canada and the USA found species richness, community composition, abundances, use, nesting densities, nesting success or productivity were similar or lower on grazed compared with ungrazed areas. One found that several species were excluded by grazing. *Assessment: trade-offs between benefits and harms (effectiveness 43%; certainty 65%; harms 45%).*

http://www.conservationevidence.com/actions/349

#### **Employ grazing in natural grasslands**

Five of 12 studies from the USA and Canada found that densities of some species were higher on grazed than ungrazed sites. Eight studies from the USA, Canada and France found that some or all species studied were found at similar or lower densities on grazed compared to ungrazed sites or those under other management. Two controlled studies from the USA and Canada found that nesting success was higher on grazed than ungrazed sites. Five studies from the USA and Canada found that nesting success was similar or lower on grazed sites. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 60%; harms 50%).*

#### **Employ grazing in non-grassland habitats**

One of eight studies found more bird species on grazed than unmanaged sites, apart from in drought years. A study from the Netherlands found the number of species in a mixed habitat wetland site declined with increased grazing. Three studies in Sweden, the Netherlands and Kenya found that the overall abundance or densities of some species were higher in grazed than ungrazed sites. Four studies in Europe and Kenya found that some species were absent or at lower densities on grazed compared to ungrazed sites or those under different management. Five studies from across the world found no differences in abundances or densities of some or all species between grazed sites and those that were ungrazed or under different management. Two studies from the UK found that productivity was lower in grazed than ungrazed sites. A study from the UK found that songbirds and invertebrate-eating species, but not crows were more common on rough-grazed habitats than intensive pasture. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 67%; harms 40%)*.

http://www.conservationevidence.com/actions/350

#### **Manage water level in wetlands**

Three studies (of six) from the USA, UK and Canada found that different species were more abundant at different water heights. One found that diversity levels also changed. One study found that great bitterns in the UK established territories earlier when deep water levels were maintained, but productivity did not vary. A study from Spain found that water management successfully retained water near a greater flamingo nesting area, but did not measure the effects on productivity or survival. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 41%; harms 35%).*

http://www.conservationevidence.com/actions/355

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (forests)**

Seven studies from Europe and the USA found that species richness, total density or densities of some species were higher in areas with mid- or understorey management compared to areas without management. Four studies also used other interventions. Seven studies from the USA and Canada found that species richness, densities, survival or competition for nest sites were similar or lower in areas with mid- or understorey control. Two studies investigated several interventions at once. Two studies from Canada found higher nest survival in forests with removal of deciduous trees compared to controls. One study found that chicks foraging success was higher in areas with cleared understorey vegetation compared to burned areas, but lower than under other managements. *Assessment: tradeoffs between benefits and harms (effectiveness 40%; certainty 75%; harms 40%).*

http://www.conservationevidence.com/actions/335

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (mowing or cutting natural grasslands)**

Two of six studies found higher densities of birds or nests on mown grasslands compared to unmanaged or burned areas. Two studies found lower densities or nests of some species and two found no differences in nesting densities or community composition on mown compared to unmown areas. One study from the USA found that grasshopper sparrow nesting success was higher on mown than grazed areas. One study from the USA found that duck nesting success was similar on cut and uncut areas. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 50%; harms 39%).*

http://www.conservationevidence.com/actions/338

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (mowing or cutting semi-natural grasslands/pastures)**

One of four studies found that wader populations increased following annual cutting of semi-natural grasslands. One study from the UK found that ducks grazed at higher densities on cut areas. Another study in the UK found that goose grazing densities were unaffected by cutting frequency. One study from the USA found that Henslow's sparrows were more likely to be recaptured on unmown than mown grasslands. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 40%; harms 20%).*

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (shrublands)**

One of seven studies found that overall bird diversity and bird density was similar between chained areas, burned areas and controls. One found that overall diversity and abundance was lower on mown sites than controls, but that grassland-specialist species were present on managed sites. Five studies from the USA and Europe found than some species were at greater densities or abundances on sites with mechanical vegetation control than on sites with burning or no management. Three studies from the USA found that some species were less abundant on sites with mechanical vegetation removal. One study from the USA found no differences between areas cut in winter and summer. *Assessment: trade-offs between benefits and harms (effectiveness 43%; certainty 54%; harms 30%).*

http://www.conservationevidence.com/actions/337

#### **Raise water levels in ditches or grassland**

One of seven studies found that three waders were found to have recolonised a UK site or be found at very high densities after water levels were raised. Three studies from Europe found that raising water levels on grassland provided habitat for waders. A study from Denmark found that oystercatchers did not nest at higher densities on sites with raised water levels. A study from the UK found that birds visited sites with raised water levels more frequently than other fields, but another UK study found that feeding rates did not differ between sites with raised water levels and those without. A study from the USA found that predation rates on seaside sparrow nests increased as water levels were raised. *Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 55%; harms 25%).*

http://www.conservationevidence.com/actions/354

#### **Thin trees within forests**

One study of 14 (from the USA) found higher bird species richness in sites with tree thinning and several other interventions, compared to unmanaged sites. Three studies from the UK and USA found no such differences. Seven studies (four investigating multiple interventions) found that overall bird abundance or the abundance of some species was higher in thinned plots, compared to those under different management. Five studies found that found that abundances were similar, or that some species were less abundant in areas with thinning. Two studies from the USA found no effect of thinning on wood thrushes, a species thought to be sensitive to it. A study from the USA found that a higher proportion of nests were in nest boxes in a thinned site, compared to a control. A study from the USA found no differences in bird abundances between burned sites with highretention thinning, compared to low-retention sites. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 60%; harms 30%).*

http://www.conservationevidence.com/actions/328

### **Use prescribed burning (grasslands)**

Four of 21 studies found that overall species richness and community composition did not vary between burned and unburned sites. Nine studies from across the world found that at least some species were more abundant or at higher densities in burned than unburned areas or areas under different management. Fourteen studies found that at least one species was at similar or lower abundances on burned areas. Responses varied depending on how soon after fires monitoring occurred. One study from the USA found that Florida grasshopper sparrow had significantly higher reproductive success soon after burns, whilst another found that dickcissel reproductive success was higher in patch-burned than burned and grazed areas. *Assessment: trade-offs between benefits and harms (effectiveness 45%; certainty 60%; harms 40%).*

http://www.conservationevidence.com/actions/322

### **Use prescribed burning (pine forests)**

Four of 28 studies in the USA found higher species richness, densities or abundances in sites with prescribed burning, tree thinning and in one case mid- or understorey control compared to controls. Fourteen studies found that some species were more abundant, or had higher productivities or survival in burned or burned and thinned areas than control areas. One study found that effects varied with geography and habitat. Fifteen studies found no differences in species richness or densities, community composition, productivity, behaviour or survival between sites with prescribed burning or burning and thinning, and controls or sites with other management. One study found that foraging success of chicks was lower in burned areas. Three studies found effects did not vary with burn season. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 77%; harms 35%).*

http://www.conservationevidence.com/actions/318

#### **Use prescribed burning (savannahs)**

One of five studies found that burned areas of savannah tended to have more birds and species than control or grazed areas, although burned sites showed significant annual variation unlike grazed sites. A study from Australia found that effects on bird abundances depended on burn season and habitat type. Two studies in the USA found that some open country species were more common in burned areas than unburned. A study from the USA found that two eastern bluebirds successfully raised chicks after a local prescribed burn. *Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 50%; harms 35%).*

http://www.conservationevidence.com/actions/320

#### **Use prescribed burning (shrublands)**

One of eight studies found that overall bird densities were similar between burned and unburned areas, whilst another found that species numbers and densities did not vary between areas burned in summer or winter. Three studies found that some species were more abundant on areas that were burned. Four found that species densities were similar or lower on burned compared to control areas or those under different management. One study found that sage sparrows chose different nest sites before and after burning. Another found no differences in greater sage grouse movement between burned and unburned areas. *Assessment: trade-offs between benefits and harms (effectiveness 43%; certainty 50%; harms 45%).*

http://www.conservationevidence.com/actions/321

#### **Use selective harvesting/logging instead of clearcutting**

Six of seven studies from the USA and Canada found that some species were more, and other less, abundant in selectively logged forests compared to unlogged stands, or those under other management. One study found that differences between treatments were not consistent. A study from the USA found that species richness of cavity-nesting birds was lower in selectively logged forests than in clearcuts. One study from the USA found that brood parasitism was higher in selectively logged forests for two species and lower for two others, compared to control stands. *Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 60%; harms 30%).*

http://www.conservationevidence.com/actions/331

#### **Unknown effectiveness (limited evidence)**

#### **Clearcut and re-seed forests**

One of two studies from the USA found that stands of pines replanted with native species held more species typical of scrub habitats than stands under different management. The other study found similar bird densities in clearcut and re-seeded sites and those under different management. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/327

#### **Coppice trees**

One of three studies found a population increase in European nightjars on a UK site after the introduction of coppicing and other interventions. Two studies from the UK and USA found that the use of coppices by some bird species declined over time. A UK study found that species richness decreased with the age of a coppice, but that some species were more abundant in older stands. *Assessment: unknown effectiveness — limited evidence (effectiveness 34%; certainty 30%; harms 30%).*

http://www.conservationevidence.com/actions/329

#### **Fertilise grasslands**

All four studies captured (all from the UK) found that more geese grazed on fertilised areas of grass more than control areas. Two investigated cutting and fertilizing at the same time. One study found that fertilised areas were used less than re-seeded areas. One study found that fertilisation had an effect at applications of 50 kg N/ha, but not at 18 kg N/ha. Another found that the effects of fertilisation did not increase at applications over 80 kg N/ha. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 35%; harms 7%).*

http://www.conservationevidence.com/actions/353

#### **Manage woodland edges for birds**

One of three studies found that a local population of European nightjars increased at a UK site following the start of a management regime that included the management of woodland edges for birds. Two studies of an experiment in the USA found that bird abundance (but not species richness or nesting success) was higher in woodland edges managed for wildlife than unmanaged edges. *Assessment: unknown effectiveness — limited evidence (effectiveness 55%; certainty 39%; harms 30%).*

http://www.conservationevidence.com/actions/334

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (reedbeds)**

One of three studies found that warblers nested at lower densities in cut areas of reeds. Productivity and success did not vary between treatments. A study from Denmark found that geese grazed at the highest densities on reedbeds cut 5–12 years previously. One study in the UK found that cutting reeds and changing water levels did not affect great bittern breeding productivity, but did delay territory establishment. *Assessment: unknown effectiveness — limited evidence (effectiveness 15%; certainty 36%; harms 14%).*

http://www.conservationevidence.com/actions/340

## **Manually control or remove midstorey and ground-level vegetation (including mowing, chaining, cutting etc.) (savannahs)**

A study in Argentina found that in summer, but not overall, bird abundance and species richness was lower in an area where shrubs were removed compared to a control. Community composition also differed between treatments. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 30%).*

#### **Plant trees to act as windbreaks**

One of two studies found that a population of European nightjars increased at a UK site after multiple interventions including the planting of windbreak trees. A study from the USA found that such trees appeared to disrupt lekking behaviour in greater prairie chickens. *Assessment: unknown effectiveness — limited evidence (effectiveness 12%; certainty 25%; harms 20%).*

http://www.conservationevidence.com/actions/351

#### **Plough habitats**

One of four studies found that bird densities were higher on ploughed wetlands in the USA than unploughed ones. Three studies of one experiment in the UK found that few whimbrels nested on areas of heathland ploughed and re-seeded, but that they were used for foraging in early spring. There were no differences in chick survival between birds that used ploughed and re-seeded heathland and those that did not. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 36%; harms 10%).*

http://www.conservationevidence.com/actions/358

#### **Provide deadwood/snags in forests (adding woody debris to forests)**

One study from Australia found that brown treecreeper numbers were higher in plots with large amounts of dead wood added compared to plots with less or no debris added. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 29%; harms 0%).*

http://www.conservationevidence.com/actions/344

#### **Remove coarse woody debris from forests**

Two studies from the USA found that some species increased in sites with woody debris removal. One found that overall breeding bird abundance and diversity were lower in removal plots; the other that survival of blackchinned hummingbird nests was lower. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 33%; harms 60%).*

## **Replace non-native species of tree/shrub**

A study from the USA found that the number of black-chinned hummingbird nests increased after fuel reduction and the planting of native species, but that the increase was smaller than at sites without planting. *Assessment: unknown effectiveness — limited evidence (effectiveness 5%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/341

#### **Re-seed grasslands**

One of two studies from the UK found that geese grazed at higher densities on re-seeded grasslands than on control or fertilised grasslands. Another study from the UK found that geese grazed at higher densities on areas sown with clover, rather than grass seed. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/352

#### **Use environmentally sensitive flood management**

One of two studies found more bird territories on a stretch of river in the UK with flood beams, compared to a channelized river. The other found that 13 out of 20 species of bird increased at sites in the USA where a river's hydrological dynamics were restored. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 26%; harms 0%).*

http://www.conservationevidence.com/actions/356

#### **Use fire suppression/control**

All three studies we captured, from the USA, UK and Australia, found that some bird species increased after fire suppression, and in one case that woodland species appeared in a site. Two studies (from the UK and USA) found that some species declined following fire suppression. The USA study identified open country species as being negatively affected. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 34%; harms 30%).*

#### **Use greentree reservoir management**

A study from the USA found that fewer mid- and under-storey birds were found at a greentree reservoir site than at a control site. Canopy-nesting species were not affected. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%; harms 40%).*

http://www.conservationevidence.com/actions/357

#### **Use prescribed burning (Australian sclerophyll forest)**

Two of three studies from Australia found no differences in bird species richness in burned sites compared to unburned areas. All three found differences in species assemblages, with some species lost and others gained from areas after fire. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 31%; harms 30%).*

http://www.conservationevidence.com/actions/319

#### **Use shelterwood cutting instead of clearcutting**

A study from the USA found that bird community composition differed between shelterwood stands and those under other forestry practices: some species were more abundant, others less so. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 20%; harms 40%).*

http://www.conservationevidence.com/actions/333

#### **Use variable retention management during forestry operations**

A study from the USA found that nine species were more abundant and five less so in stands under variable retention management, compared to unmanaged stands. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 20%; harms 25%).*

#### **Likely to be ineffective or harmful**

## **Apply herbicide to mid- and understorey vegetation**

One of seven studies from North America found that bird species richness in a forest declined after deciduous trees were treated with herbicide. Three studies found increases in total bird densities, or those of some species, after herbicide treatment, although one found no differences between treatment and control areas. One study found that densities of one species decreased and another remained steady after treatment. Three studies found that nest survival was lower in herbicide-treated areas and one found lower nesting densities. One study found that northern bobwhite chicks higher had foraging success in forest areas treated with herbicide compared to under other managements. *Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 50%; harms 60%).*

http://www.conservationevidence.com/actions/346

#### **Treat wetlands with herbicides**

All four studies from the USA found higher densities of birds in wetlands sprayed with herbicide, compared with unsprayed areas. Two found that some species were at lower densities compared to unsprayed areas or those under other management. *Assessment: likely to be ineffective or harmful (effectiveness 30%; certainty 42%; harms 40%).*

http://www.conservationevidence.com/actions/347

#### **Use prescribed burning (coastal habitats)**

One study from the USA found that breeding seaside sparrow numbers decreased the year a site was burned, but were higher than on an unburned site the following year. One study in Argentina found that tall-grass specialist species were lost from burned areas in the year of burning, but that some habitats recovered by the following year. One study from the USA found no differences in nest predation rates between burned and unburned areas for two years after burning. *Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 40%; harms 30%).*

#### **Use prescribed burning (deciduous forests)**

One of four studies found that bird species richness was similar in burned and unburned aspen forests, although relative abundances of some species changed. A study in the USA found no changes in community composition in oak and hickory forests following burning. One study in the USA found no differences in wood thrush nest survival in burned and unburned areas. Another study in the USA found a reduction in black-chinned hummingbird nests following fuel reduction treatments including burning. *Assessments: likely to be ineffective or harmful (effectiveness 32%; certainty 60%; harms 30%).*

http://www.conservationevidence.com/actions/317

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Protect nest trees before burning

# 3.10 Habitat restoration and creation


#### **Beneficial**

#### **Restore or create forests**

Thirteen of 15 studies from across the world found that restored forests were similar to in-tact forests, that species returned to restored sites, that species recovered significantly better at restored than unrestored sites or that bird species richness, diversity or abundances in restored forest sites increased over time. One study also found that restoration techniques themselves improved over time. Nine studies found that some species did not return to restored forests or were less common and a study found that territory densities decreased over time. A study from the USA found that no more birds were found in restored sites, compared with unrestored. One study investigated productivity and found it was similar between restored and intact forests. A study from the USA found that planting fastgrowing species appeared to provide better habitat than slower-growing trees. *Assessment: beneficial (effectiveness 65%; certainty 76%; harms 0%).*

http://www.conservationevidence.com/actions/360

### **Restore or create wetlands and marine habitats (inland wetlands)**

All eleven studies from the USA and Canada found that birds used restored or created wetlands. Two found that rates of use and species richness were similar or higher than on natural wetlands. One found that use was higher than on unrestored wetlands. Three studies from the USA and Puerto Rico found that restored wetlands held lower densities and fewer species or had similar productivity compared to natural wetlands. Two studies in the USA found that semi-permanent restored and larger wetlands were used more than temporary or seasonal or smaller ones. *Assessment: beneficial (effectiveness 70%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/366

#### **Likely to be beneficial**

#### **Restore or create grassland**

Three of 23 studies found that species richness on restored grasslands was higher than unrestored habitats, or similar to remnant grassland, and three found that target species used restored grassland. Two studies from the USA found that diversity or species richness fell after restoration or was lower than unrestored sites. Seven studies from the USA and UK found high use of restored sites, or that such sites held a disproportionate proportion of the local population of birds. Two studies found that densities or abundances were lower on restored than unrestored sites, potentially due to drought conditions in one case. Five studies found that at least

#### *Bird Conservation*

some bird species had higher productivities in restored sites compared to unrestored; had similar or higher productivities than natural habitats; or had high enough productivities to sustain populations. Three studies found that productivities were lower in restored than unrestored areas, or that productivities on restored sites were too low to sustain populations. A study from the USA found that older restored fields held more nests, but fewer species than young fields. Three studies found no differences between restoration techniques; two found that sowing certain species increased the use of sites by birds. *Assessment: likely to be beneficial (effectiveness 45%; certainty 70%; harms 0%).*

http://www.conservationevidence.com/actions/361

#### **Restore or create traditional water meadows**

Four out of five studies found that the number of waders or wildfowl on UK sites increased after the restoration of traditional water meadows. One study from Sweden found an increase in northern lapwing population after an increase in meadow management. One study found that lapwing productivity was higher on meadows than some habitats, but not others. *Assessment: likely to be beneficial (effectiveness 65%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/363

## **Restore or create wetlands and marine habitats (coastal and intertidal wetlands)**

All six studies from the USA and UK found that bird species used restored or created wetlands. Two found that numbers and/or diversity were similar to in natural wetlands and one that numbers were higher than in unrestored sites. Three found that bird numbers on wetlands increased over time. Two studies from the UK found that songbirds and waders decreased following wetland restoration, whilst a study from the USA found that songbirds were more common on unrestored sites than restored wetlands. *Assessment: likely to be beneficial (effectiveness 65%; certainty 55%; harms 3%).*

#### **Unknown effectiveness (limited evidence)**

#### **Restore or create shrubland**

Three studies from the UK, USA and the Azores found local bird population increases after shrubland restoration. Two studies investigated multiple interventions and one found an increase from no birds to one or two pairs. One study from the UK found that several interventions, including shrubland restoration, were negatively related to the number of young grey partridges per adult bird on sites. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 20%; harms 3%).*

http://www.conservationevidence.com/actions/364

#### **Restore or create wetlands and marine habitats (kelp forests)**

One study in the USA found that the densities of five of the nine bird species increased following kelp forest restoration. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/368

#### **Restore or create wetlands and marine habitats (lagoons)**

One study in the UK found that large numbers of bird species used and bred in a newly-created lagoon. *Assessment: unknown effectiveness — limited evidence (effectiveness 61%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/369

#### **No evidence found (no assessment)**


# 3.11 Threat: Invasive alien and other problematic species

This assessment method for this chapter is described in Walsh, J. C., Dicks, L. V. & Sutherland, W. J. (2015) The effect of scientific evidence on conservation practitioners' management decisions. Conservation Biology, 29: 88–98. No harms were assessed for sections 3.11.1, 3.11.2, 3.11,3 and 3.11.4.

## 3.11.1 Reduce predation by other species


#### **Beneficial**

#### **Control mammalian predators on islands**

Of the 33 studies from across the world, 16 described population increases or recolonisations in at least some of the sites studied and 18 found higher reproductive success or lower mortality (on artificial nests in one case). Two studies that investigated population changes found only partial increases, in black oystercatchers *Haematopus bachmani* and two gamebird species, respectively. Eighteen of the studies investigated rodent control; 12 cat *Felis catus* control and 6 various other predators including pigs *Sus scrofa* and red foxes *Vulpes*. The two that found only partial increases examined cat, fox and other larger mammal removal. *Assessment: beneficial (effectiveness 81%; certainty 78%).*

http://www.conservationevidence.com/actions/373

#### **Remove or control predators to enhance bird populations and communities**

Both a meta-analysis and a systematic review (both global) found that bird reproductive success increased with predator control and that either postbreeding or breeding-season populations increased. The systematic review found that post-breeding success increased with predator control on mainland, but not islands. *Assessment: beneficial (effectiveness 66%; certainty 71%).*

http://www.conservationevidence.com/actions/371

#### **Likely to be beneficial**

#### **Control avian predators on islands**

Seven out of ten studies from North America, Australia and Europe found that controlling avian predators led to increased population sizes, reduced mortality, increased reproductive success or successful translocation of seabirds on islands. Two controlled studies on European islands found little effect of controlling crows on reproductive success in raptors or gamebirds. One study in the UK found that numbers of terns and small gulls on gravel islands declined despite the attempted control of large gulls. *Assessment: likely to be beneficial (effectiveness 50%; certainty 45%).*

#### **Unknown effectiveness (limited evidence)**

#### **Control invasive ants on islands**

A single study in the USA found that controlling the invasive tropical fire ant *Solenopsis geminata*, but not the big-headed ant *Pheidole megacephala,* led to lower rates of injuries and temporarily higher fledging success than on islands without ant control. The authors note that very few chicks were injured by *P. megacephala* on either experimental or control islands. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 15%).*

http://www.conservationevidence.com/actions/383

#### **Reduce predation by translocating predators**

Two studies from France and the USA found local population increases or reduced predation following the translocation of predators away from an area. *Assessment: unknown effectiveness — limited evidence (effectiveness 27%; certainty 20%).*

http://www.conservationevidence.com/actions/393

#### **Evidence not assessed**

#### **Control predators not on islands**

A study from the UK found higher bird community breeding densities and fledging success rates in plots with red fox *Vulpes vulpes* and carrion crow *Corvus corone* control. Of the 25 taxa-specific studies, only five found evidence for population increases with predator control, whilst one found a population decrease (with other interventions also used); one found lower or similar survival, probably because birds took bait. Nineteen studies found some evidence for increased reproductive success or decreased predation with predator control, with three studies (including a metaanalysis) finding no evidence for higher reproductive success or predation with predator control or translocation from the study site. One other study found evidence for increases in only three of six species studied. Most studies studied the removal of a number of different mammals, although several also removed bird predators, mostly carrion crows and gulls *Larus*  spp. *Assessment: this intervention has not been assessed.*

## 3.11.2 Reduce incidental mortality during predator eradication or control


#### **Unknown effectiveness (limited evidence)**

#### **Distribute poison bait using dispensers**

A study from New Zealand found that South Island robin survival was higher when bait for rats and mice was dispensed from feeders, compared to being scattered. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 25%).*

http://www.conservationevidence.com/actions/157

## **Use coloured baits to reduce accidental mortality during predator control**

Two out of three studies found that dyed baits were consumed at lower rates by songbirds and kestrels. An *ex situ* study from Australia found that dyeing food did not reduce its consumption by bush thick-knees. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 30%).*

http://www.conservationevidence.com/actions/182

#### **Use repellents on baits**

A study in New Zealand found that repellents reduced the rate of pecking at baits by North Island robins. A study from the USA found that treating bait with repellents did not reduce consumption by American kestrels. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%).*

#### **Evidence not assessed**

## **Do birds take bait designed for pest control?**

Two studies from New Zealand and Australia, one *ex situ*, found no evidence that birds took bait meant for pest control. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/395

## 3.11.3 Reduce nest predation by excluding predators from nests or nesting areas


#### **Likely to be beneficial**

## **Physically protect nests from predators using non-electric fencing**

Two of four studies from the UK and the USA found that fewer nests failed or were predated when predator exclusion fences were erected. Two studies found that nesting and fledging success was no higher when fences were used, one found that hatching success was higher. *Assessment: likely to be beneficial (effectiveness 45%; certainty 48%).*

http://www.conservationevidence.com/actions/183

#### **Physically protect nests with individual exclosures/ barriers or provide shelters for chicks**

Nine of 23 studies found that fledging rates or productivity were higher for nests protected by individual barriers than for unprotected nests. Two found no higher productivity. Fourteen studies found that hatching rates or survival were higher, or that predation was lower for protected nests. Two found no differences between protected and unprotected nests and one found that adults were harassed by predators at protected nests. One study found that chick shelters were not used much and a review found that some exclosure designs were more effective than others. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%).*

> http://www.conservationevidence.com/actions/397 http://www.conservationevidence.com/actions/398 http://www.conservationevidence.com/actions/399 http://www.conservationevidence.com/actions/400

#### **Protect bird nests using electric fencing**

Two of six studies found increased numbers of terns or tern nests following the erection of an electric fence around colonies. Five studies found higher survival or productivity of waders or seabirds when electric fences were used and one found lower predation by mammals inside electric fences. One study found that predation by birds was higher inside electric fences. *Assessment: likely to be beneficial (effectiveness 60%; certainty 59%).*

#### **Use artificial nests that discourage predation**

Three out of five studies from North America found lower predation rates or higher nesting success for wildfowl in artificial nests, compared with natural nests. An *ex situ* study found that some nest box designs prevented raccoons from entering. A study found that wood ducks avoided antipredator nest boxes but only if given the choice of unaltered nest boxes. *Assessment: likely to be beneficial (effectiveness 59%; certainty 54%).*

http://www.conservationevidence.com/actions/402

#### **Unknown effectiveness (limited evidence)**

#### **Guard nests to prevent predation**

Nest guarding can be used as a response to a range of threats and is therefore discussed in 'General responses to small/declining populations *—* Guard nests'. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%).*

http://www.conservationevidence.com/actions/411

#### **Plant nesting cover to reduce nest predation**

Studies relevant to this intervention are discussed in 'Threat: Agriculture'. *Assessment: unknown effectiveness — limited evidence (effectiveness 28%; certainty 30%)*.

http://www.conservationevidence.com/actions/405

#### **Protect nests from ants**

A study from the USA found that vireo nests protected from ants with a physical barrier and a chemical repellent had higher fledging success than unprotected nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 17%).*

http://www.conservationevidence.com/actions/410

#### **Use multiple barriers to protect nests**

One of two studies found that plover fledging success in the USA was no higher when an electric fence was erected around individual nest exclosures, compared to when just the exclosures were present. A study from the USA found that predation on chicks was lower when one of two barriers around nests was removed early, compared to when it was left for three more days. *Assessment: unknown effectiveness — limited evidence (effectiveness 7%; certainty 17%).*

http://www.conservationevidence.com/actions/404

#### **Use naphthalene to deter mammalian predators**

A study from the USA found that predation rates on artificial nests did not differ when naphthalene moth balls were scattered around them. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%).*

http://www.conservationevidence.com/actions/408

#### **Use snakeskin to deter mammalian nest predators**

A study from the USA found that flycatcher nests were predated less frequently if they had a snakeskin wrapped around them. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 15%).*

http://www.conservationevidence.com/actions/406

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


#### **Evidence not assessed**

#### **Can nest protection increase nest abandonment?**

One of four studies (from the USA) found an increase in abandonment after nest exclosures were used. Two studies from the USA and Sweden found no increases in abandonment when exclosures were used and a review from the USA found that some designs were more likely to cause abandonment than others. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/401

## **Can nest protection increase predation of adults and chicks?**

Four of five studies from the USA and Sweden found that predation on chicks and adults was higher when exclosures were used. One of these found that adults were harassed when exclosures were installed and the chicks rapidly predated when they were removed. One study from Sweden found that predation was no higher when exclosures were used. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/403

## 3.11.4 Reduce mortality by reducing hunting ability or changing predator behaviour


### **Unknown effectiveness (limited evidence)**

#### **Reduce predation by translocating nest boxes**

Two European studies found that predation rates were lower for translocated nest boxes than for controls. *Assessment: unknown effectiveness — limited evidence (effectiveness 48%; certainty 25%).*

#### **Use collar-mounted devices to reduce predation**

Two replicated randomised and controlled studies in the UK and Australia found that fewer birds were returned by cats wearing collars with antihunting devices, compared to cats with control collars. No differences were found between different devices. *Assessment: unknown effectiveness — limited evidence (effectiveness 48%; certainty 35%).*

http://www.conservationevidence.com/actions/416

#### **Use supplementary feeding to reduce predation**

One of three studies found that fewer grouse chicks were taken to harrier nests when supplementary food was provided to the harriers, but no effect on grouse adult survival or productivity was found. One study from the USA found reduced predation on artificial nests when supplementary food was provided. Another study from the USA found no such effect. *Assessment: unknown effectiveness — limited evidence (effectiveness 13%; certainty 20%).*

http://www.conservationevidence.com/actions/417

#### **Unlikely to be beneficial**

#### **Use aversive conditioning to reduce nest predation**

Nine out of 12 studies found no evidence for aversive conditioning or reduced nest predation after aversive conditioning treatment stopped. Ten studies found reduced consumption of food when it was treated with repellent chemicals, i.e. during the treatment. Three, all studying avian predators, found some evidence for reduced consumption after treatment but these were short-lived trials or the effect disappeared within a year. *Assessment: unlikely to be beneficial (effectiveness 9%; certainty 60%).*

> http://www.conservationevidence.com/actions/418 http://www.conservationevidence.com/actions/419

# 3.11.5 Reduce competition with other species for food and nest sites

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing competition with other species for food and nest sites?**


## **Likely to be beneficial**

## **Reduce inter-specific competition for food by removing or controlling competitor species**

Three out of four studies found that at least some of the target species increased following the removal or control of competitor species. Two studies found that some or all target species did not increase, or that there was no change in kleptoparasitic behaviour of competitor species after control efforts. *Assessment: likely to be beneficial (effectiveness 44%; certainty 40%; harms 0%).*

#### **Unknown effectiveness (limited evidence)**

#### **Protect nest sites from competitors**

Two studies from the USA found that red-cockaded woodpecker populations increased after the installation of 'restrictor plates' around nest holes to prevent larger woodpeckers for enlarging them. Several other interventions were used at the same time. A study from Puerto Rico found lower competition between species after nest boxes were altered. A study from the USA found weak evidence that exclusion devices prevented house sparrows from using nest boxes and another study from the USA found that fitting restrictor plates to red-cockaded woodpecker holes reduced the number that were enlarged by other woodpeckers. *Assessment: unknown effectiveness — limited evidence (effectiveness 39%; certainty 24%; harms 5%).*

http://www.conservationevidence.com/actions/426

#### **Reduce competition between species by providing nest boxes**

A study from the USA found that providing extra nest boxes did not reduce the rate at which common starlings usurped northern flickers from nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 16%; harms 0%).*

http://www.conservationevidence.com/actions/427

#### **Reduce inter-specific competition for nest sites by modifying habitats to exclude competitor species**

A study from the USA found that clearing midstorey vegetation did not reduce the occupancy of red-cockaded woodpecker nesting holes by southern flying squirrels. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 12%; harms 0%).*

## **Reduce inter-specific competition for nest sites by removing competitor species (ground nesting seabirds)**

Four studies from Canada and the UK found increased tern populations following the control or exclusion of gulls, and in two cases with many additional interventions. Two studies from the UK and Canada found that controlling large gulls had no impact on smaller species. Two studies from the USA and UK found that exclusion devices successfully reduced the numbers of gulls at sites, although one found that they were only effective at small colonies and the other found that methods varied in their effectiveness and practicality. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 31%; harms 14%).*

http://www.conservationevidence.com/actions/422

## **Reduce inter-specific competition for nest sites by removing competitor species (songbirds)**

Two studies from Australia found increases in bird populations and species richness after control of noisy miners. A study from Italy found that blue tits nested in more nest boxes when hazel dormice were excluded from boxes over winter. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 22%; harms 0%).*

http://www.conservationevidence.com/actions/424

## **Reduce inter-specific competition for nest sites by removing competitor species (woodpeckers)**

Two studies in the USA found red-cockaded woodpecker populations increased following the removal of southern flying squirrels, in one case along with other interventions. A third found that red-cockaded woodpecker reintroductions were successful when squirrels were controlled. One study found fewer holes were occupied by squirrels following control efforts, but that occupancy by red-cockaded woodpeckers was no higher. *Assessment: unknown effectiveness — limited evidence (effectiveness 34%; certainty 28%; harms 0%).*

## 3.11.6 Reduce adverse habitat alteration by other species

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing adverse habitat alteration by other species?**


## **Likely to be beneficial**

## **Control or remove habitat-altering mammals**

Four out of five studies from islands in the Azores and Australia found that seabird populations increased after rabbits or other species were removed, although three studied several interventions at the same time. Two studies from Australia and Madeira found that seabird productivity increased after rabbit and house mouse eradication. *Assessment: likely to be beneficial (effectiveness 61%; certainty 41%; harms 0%).*

http://www.conservationevidence.com/actions/431

## **Reduce adverse habitat alterations by excluding problematic species (terrestrial species)**

Three studies from the USA and the UK found higher numbers of certain songbird species and higher species richness in these groups when deer were excluded from forests. Intermediate canopy-nesting species in the USA and common nightingales in the UK were the species to benefit. A study from Hawaii found mixed effects of grazer exclusion. *Assessment: likely to be beneficial (effectiveness 48%; certainty 40%; harms 0%).*

#### **Unknown effectiveness (limited evidence)**

## **Reduce adverse habitat alterations by excluding problematic species (aquatic species)**

A study in the USA found that waterbirds preferentially used wetland plots from which grass carp were excluded but moved as these became depleted over the winter. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 14%; harms 0%).*

http://www.conservationevidence.com/actions/430

#### **Remove problematic vegetation**

One of four studies (from Japan) found an increase in a bird population following the removal of an invasive plant. One study from the USA found lower bird densities in areas where a problematic native species was removed. One study from Australia found the Gould's petrel productivity was higher following the removal of native bird-lime trees, and a study from New Zealand found that Chatham Island oystercatchers could nest in preferable areas of beaches after invasive marram grass was removed. *Assessment: unknown effectiveness — limited evidence (effectiveness 43%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/432

#### **Use buffer zones to reduce the impact of invasive plant control**

A study from the USA found that no snail kite nests (built above water in cattail and bulrush) were lost during herbicide spraying when buffer zones were established around nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

## 3.11.7 Reduce parasitism and disease


### **Likely to be beneficial**

### **Remove/control adult brood parasites**

One of 12 studies, all from the Americas, found that a host species population increased after control of the parasitic cowbird, two studies found no effect. Five studies found higher productivities or success rates when cowbirds were removed, five found that some or all measures of productivity were no different. Eleven studies found that brood parasitism rates were lower after cowbird control. *Assessment: likely to be beneficial (effectiveness 48%; certainty 61%; harms 0%).*

## **Trade-off between benefit and harms**

## **Remove/treat endoparasites and diseases**

Two out of five studies found that removing endoparasites increased survival in birds and one study found higher productivity in treated birds. Two studies found no evidence, or uncertain evidence, for increases in survival with treatment and one study found lower parasite burdens, but also lower survival in birds treated with antihelmintic drugs. *Assessment: trade-offs between benefits and harms (effectiveness 48%; certainty 51%; harms 37%).*

http://www.conservationevidence.com/actions/434

#### **Unknown effectiveness (limited evidence)**

#### **Alter artificial nest sites to discourage brood parasitism**

A replicated trial from Puerto Rico found that brood parasitism levels were extremely high across all nest box designs tested. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/446

## **Exclude or control 'reservoir species' to reduce parasite burdens**

One of two studies found increased chick production in grouse when hares (carries of louping ill virus) were culled in the area, although a comment on the paper disputes this finding. A literature review found no compelling evidence for the effects of hare culling on grouse populations. *Assessment: unknown effectiveness — limited evidence (effectiveness 13%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/435

#### **Remove brood parasite eggs from target species' nests**

One of two studies found lower rates of parasitism when cowbird eggs were removed from host nests. One study found that nests from which cowbird eggs were removed had lower success than parasitised nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 20%; harms 21%).*

#### **Remove/treat ectoparasites to increase survival or reproductive success (provide beneficial nesting material)**

A study in Canada found lower numbers of some, but not all, parasites in nests provided with beneficial nesting material, but that there was no effect on fledging rates or chick condition. *Assessment: unknown effectiveness — limited evidence (effectiveness 15%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/439

## **Remove/treat ectoparasites to increase survival or reproductive success (remove ectoparasites from feathers)**

A study in the UK found that red grouse treated with spot applications had lower tick and disease burdens and higher survival than controls, whilst birds with impregnated tags had lower tick burdens only. A study in Hawaii found that CO2 was the most effective way to remove lice from feathers, although lice were not killed. *Assessment: unknown effectiveness — limited evidence (effectiveness 42%; certainty 16%; harms 0%).*

http://www.conservationevidence.com/actions/437

## **Use false brood parasite eggs to discourage brood parasitism**

A study from the USA found that parasitism rates were lower for redwinged blackbird nests with false or real cowbird eggs placed in them, than for control nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/444

#### **Unlikely to be beneficial**

#### **Remove/treat ectoparasites to increase survival or reproductive success (remove ectoparasites from nests)**

Six of the seven studies found lower infestation rates in nests treated for ectoparasites, one (that used microwaves to treat nests) did not find fewer parasites. Two studies from the USA found higher survival or lower abandonment in nests treated for ectoparasites, whilst seven studies from across the world found no differences in survival, fledging rates or productivity between nests treated for ectoparasites and controls. Two of six studies found that chicks from nests treated for ectoparasites were in better condition than those from control nests. *Assessment: unlikely to be beneficial (effectiveness 25%; certainty 58%; harms 0%).*

http://www.conservationevidence.com/actions/438

## 3.11.8 Reduce detrimental impacts of other problematic species


**Unknown effectiveness (limited evidence)**

# ● Use copper strips to exclude snails from nests

## **Unknown effectiveness (limited evidence)**

#### **Use copper strips to exclude snails from nests**

A study from Mauritius found no mortality from snails invading echo parakeet nests after the installation of copper strips around nest trees. Before installation, four chicks were killed by snails. *Assessment: unknown effectiveness — limited evidence (effectiveness 47%; certainty 15%; harms 0%).*

# 3.12.1 Industrial pollution

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for industrial pollution?**


## **Likely to be beneficial**

## **Use visual and acoustic 'scarers' to deter birds from landing on pools polluted by mining or sewage**

Two studies from Australia and the USA found that deterrent systems reduced bird mortality on toxic pools. Four of five studies from the USA and Canada found that fewer birds landed on pools when deterrents were used, one found no effect. Two studies found that radar-activated systems were more effective than randomly-activated systems. One study found that loud noises were more effective than raptor models. *Assessment: likely to be beneficial (effectiveness 50%; certainty 46%; harms 0%).*

#### **Unknown effectiveness (limited evidence)**

## **Relocate birds following oil spills**

A study from South Africa found that a high percentage of penguins relocated following an oil spill returned to and bred at their old colony. More relocated birds bred than oiled-and-cleaned birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 39%; certainty 10%; harms 5%).*

http://www.conservationevidence.com/actions/449

## **Use repellents to deter birds from landing on pools polluted by mining**

An *ex situ* study from the USA found that fewer common starlings consumed contaminated water laced with chemicals, compared to untreated water. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/453

#### **Unlikely to be beneficial**

#### **Clean birds after oil spills**

Three studies from South Africa and Australia found high survival of oiled-and-cleaned penguins and plovers, but a large study from the USA found low survival of cleaned common guillemots. Two studies found that cleaned birds bred and had similar success to un-oiled birds. After a second spill, one study found that cleaned birds were less likely to breed. Two studies found that cleaned birds had lower breeding success than un-oiled birds. *Assessment: unlikely to be beneficial (effectiveness 30%; certainty 45%; harms 5%).*

# 3.12.2 Agricultural pollution


#### **Likely to be beneficial**

## **Leave headlands in fields unsprayed (conservation headlands)**

Three studies from Europe found that several species were strongly associated with conservation headlands; two of these found that other species were not associated with them. A review from the UK found larger grey partridge populations on sites with conservation headlands. Three studies found higher grey partridge adult or chick survival on sites with conservation headlands, one found survival did not differ. Four studies found higher grey partridge productivity on sites with conservation headlands, two found similar productivities and one found a negative relationship between conservation headlands and the number of chicks per adult partridge. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

## **Provide food for vultures to reduce mortality from diclofenac**

A before-and-after trial in Pakistan found that oriental white-backed vulture mortality rates were significantly lower when supplementary food was provided, compared to when it was not. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

http://www.conservationevidence.com/actions/456

#### **Reduce pesticide, herbicide and fertiliser use generally**

One of nine studies found that the populations of some species increased when pesticide use was reduced and other interventions used. Three studies found that some or all species were found at higher densities on reducedinput sites. Five found that some of all species were not at higher densities. A study from the UK found that grey partridge chicks had higher survival on sites with reduced pesticide input. Another found that partridge broods were smaller on such sites and there was no relationship between reduced inputs and survival or the ratio of young to old birds. *Assessment: likely to be beneficial (effectiveness 55%; certainty 55%; harms 3%).*

http://www.conservationevidence.com/actions/454

#### **Unknown effectiveness (limited evidence)**

### **Reduce chemical inputs in permanent grassland management**

A study from the UK found that no more foraging birds were attracted to pasture plots with no fertiliser, compared to control plots. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/459

### **Restrict certain pesticides or other agricultural chemicals**

A before-and-study from Spain found an increase in the regional griffon vulture population following the banning of strychnine, amongst several other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 3.12.3 Air-borne pollutants


#### **Unknown effectiveness (limited evidence)**

### **Use lime to reduce acidification in lakes**

A study from Sweden found no difference in osprey productivity during a period of extensive liming of acidified lakes compared to two periods without liming. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%; harms 0%).*

## 3.12.4 Excess energy


### **Unknown effectiveness (limited evidence)**

## **Shield lights to reduce mortality from artificial lights**

A study from the USA found that fewer shearwaters were downed when security lights were shielded, compared to nights with unshielded lights. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/469

## **Turning off lights to reduce mortality from artificial lights**

A study from the UK found that fewer seabirds were downed when artificial (indoor and outdoor) lighting was reduced at night, compared to nights with normal lighting. *Assessment: unknown effectiveness — limited evidence (effectiveness 49%; certainty 10%; harms 0%).*

*Pollution*

## **Use flashing lights to reduce mortality from artificial lights**

A study from the USA found that fewer dead birds were found beneath aviation control towers with only flashing lights, compared to those with both flashing and continuous lights. *Assessment: unknown effectiveness — limited evidence (effectiveness 54%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/470

## **Use lights low in spectral red to reduce mortality from artificial lights**

Two studies from Europe found that fewer birds were attracted to lowred lights (including green and blue lights), compared with the number expected, or the number attracted to white or red lights. *Assessment: unknown effectiveness — limited evidence (effectiveness 56%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/471

#### **No evidence found (no assessment)**


# 3.13 Threat: Climate change, extreme weather and geological events

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for climate change, extreme weather and geological events?**


### **Unknown effectiveness (limited evidence)**

## **Replace nesting habitats when they are washed away by storms**

A before-and-after study found that a common tern colony increased following the replacement of nesting habitats, whilst a second found that a colony decreased. In both cases, several other interventions were used at the same time, making it hard to examine the effect of habitat provision. *Assessment: unknown effectiveness — limited evidence (effectiveness 8%; certainty 10%; harms 0%).*

## **Water nesting mounds to increase incubation success in malleefowl**

A single small trial in Australia found that watering malleefowl nests increased their internal temperature but that a single application of water did not prevent the nests drying out and being abandoned during a drought. *Assessment: unknown effectiveness — limited evidence (effectiveness 9%; certainty 10%; harms 0%).*

# 3.14 General responses to small/declining populations

## 3.14.1 Inducing breeding, rehabilitation and egg removal


#### **Unknown effectiveness (limited evidence)**

### **Rehabilitate injured birds**

Two studies of four studies from the UK and USA found that 25–40% of injured birds taken in by centres were rehabilitated and released. Three studies from the USA found that rehabilitated birds appeared to have high survival. One found that mortality rates were higher for owls than raptors. *Assessment: unknown effectiveness — limited evidence (effectiveness 36%; certainty 30%; harms 0%).*

## **Remove eggs from wild nests to increase reproductive output**

A study from Canada found that whooping crane reproductive success was higher for nests with one or two eggs removed than for controls. A study from the USA found that removing bald eagle eggs did not appear to affect the wild population and a replicated study from Mauritius found that removing entire Mauritius kestrel clutches appeared to increase productivity more than removing individual eggs as they were laid. *Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 25%; harms 5%).*

http://www.conservationevidence.com/actions/477

## **Use artificial visual and auditory stimuli to induce breeding in wild populations**

A small study from the British Virgin Islands found an increase in breeding behaviour after the introduction of visual and auditory stimulants. *Assessment: unknown effectiveness — limited evidence (effectiveness 19%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/475

## 3.14.2 Provide artificial nesting sites



## **Beneficial**

## **Provide artificial nests (falcons)**

Four studies from the USA and Europe found that local populations of falcons increased following the installation of artificial nesting sites. However, a study from Canada found no increase in the local population of falcons following the erection of nest boxes. Eight studies from across the world found that the success and productivity of falcons in nest boxes was higher than or equal to those in natural nests. Four studies from across the world found that productivity in nest boxes was lower than in natural nests, or that some falcons were evicted from their nests by owls. Four studies from across the world found no differences in productivity between nest box designs or positions, whilst two from Spain and Israel found that productivity in boxes varied between designs and habitats. Twenty-one studies from across the world found nest boxes were used by falcons, with one in the UK finding that nest boxes were not used at all. Seven studies found that position or design affected use, whilst three found no differences between design or positioning. *Assessment: beneficial (effectiveness 65%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/489

#### **Provide artificial nests (owls)**

Three studies from the UK appeared to show increases in local populations of owls following the installation of artificial nests. Another UK study found that providing nesting sites when renovating buildings maintained owl populations, whilst they declined at sites without nests. Four studies from the USA and the UK found high levels of breeding success in artificial nests. Two studies from the USA and Hungary found lower productivity or fledgling survival from breeding attempts in artificial nests, whilst a study from Finland found that artificial nests were only successful in the absence of larger owls. Four studies from the USA and Europe found that artificial nests were used as frequently as natural sites. Five studies from across the world found that owls used artificial nests. Seven studies found that nest position or design affected occupancy or productivity. However four studies found occupancy and/or productivity did not differ between different designs of nest box. *Assessment: beneficial (effectiveness 65%; certainty 66%; harms 5%).*

http://www.conservationevidence.com/actions/490

#### **Provide artificial nests (songbirds)**

Only three out of 66 studies from across the world found low rates of nest box occupancy in songbirds. Low rates of use were seen in thrushes, crows, swallows and New World warblers. Thrushes, crows, finches, swallows, wrens, tits, Old World and tyrant flycatchers, New World blackbirds, sparrows, waxbills, starlings and ovenbirds all used nest boxes. Five studies from across the world found higher population densities or growth rates, and one study from the USA found higher species richness, in areas with nest boxes. Twelve studies from across the world found that productivity in nest boxes was higher than or similar to natural nests. One study found there were more nesting attempts in areas with more nest boxes, although a study from Canada found no differences in productivity between areas with different nest box densities. Two studies from Europe found lower predation of species using nest boxes but three studies from the USA found

Visit **www.conservationevidence.com** for full text and references 241

#### *Bird Conservation*

low production in nest boxes. Thirteen studies from across the world found that use, productivity or usurpation rate varied with nest box design, whilst seven found no difference in occupation rates or success between different designs. Similarly, fourteen studies found different occupation or success rates depending on the position of artificial nest sites but two studies found no such differences. *Assessment: beneficial (effectiveness 67%; certainty 85%; harms 0%).*

http://www.conservationevidence.com/actions/498

### **Provide artificial nests (wildfowl)**

Six studies from North America and Europe found that wildfowl populations increased with the provision of artificial nests, although one study from Finland found no increase in productivity in areas with nest boxes. Nine out of twelve studies from North America found that productivity was high in artificial nests. Two studies found that success for some species in nest boxes was lower than for natural nests. Nineteen studies from across the world found that occupancy rates varied from no use to 100% occupancy. Two studies found that occupancy rates were affected by design or positioning. Three studies from North America found that nest boxes could have other impacts on reproduction and behaviour. *Assessment: beneficial (effectiveness 62%; certainty 76%; harms 0%).*

http://www.conservationevidence.com/actions/482

#### **Likely to be beneficial**

### **Clean artificial nests to increase occupancy or reproductive success**

Five out of ten studies from North America and Europe found that songbirds preferentially nested in cleaned nest boxes or those sterilised using microwaves, compared to used nest boxes. One study found that the preference was not strong enough for birds to switch nest boxes after they were settled. One study found that birds avoided heavily-soiled nest boxes. Two studies birds had a preference for used nest boxes and one found no preference for cleaned or uncleaned boxes. None of the five studies that examined it found any effect of nest box cleanliness on nesting success or parasitism levels. *Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 15%).*

http://www.conservationevidence.com/actions/499

#### **Provide artificial nests (burrow-nesting seabirds)**

Four studies from across the world found population increases or population establishment following the provision of nest boxes. In two cases this was combined with other interventions. Six studies from across the world found high occupancy rates for artificial burros by seabirds but three studies from across the world found very low occupancy rates for artificial burrows used by petrels. Eight studies from across the world found that the productivity of birds in artificial burrows was high although two studies from the USA and the Galapagos found low productivity in petrels. *Assessment: likely to be beneficial (effectiveness 60%; certainty 71%; harms 5%).*

http://www.conservationevidence.com/actions/481

#### **Provide artificial nests (divers/loons)**

Three studies from the UK and the USA found increases in loon productivity on lakes provided with nesting rafts. A study in the UK found that usage of nesting rafts varied between sites. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/478

#### **Provide artificial nests (ground- and tree-nesting seabirds)**

Three studies from the UK and the Azores found increases in gull and tern populations following the provision of rafts/islands or nest boxes alongside other interventions. Five studies from Canada and Europe found that terns used artificial nesting sites. A study from the USA found that terns had higher nesting success on artificial rafts in some years and a study from Japan found increased nesting success after provision of nesting substrate. Design of nesting structure should be considered. *Assessment: likely to be beneficial (effectiveness 60%; certainty 49%; harms 0%).*

## **Provide artificial nests (oilbirds)**

A study in Trinidad and Tobago found an increase in the size of an oilbird colony after the creation of artificial nesting lodges. *Assessment: likely to be beneficial (effectiveness 50%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/491

## **Provide artificial nests (raptors)**

Nine studies from North America and Spain found that raptors used artificial nesting platforms. Two studies from the USA found increases in populations or densities following the installation of platforms. Three studies describe successful use of platforms but three found lower productivity or failed nesting attempts, although these studies only describe a single nesting attempt. *Assessment: likely to be beneficial (effectiveness 55%; certainty 55%; harms 0%).*

http://www.conservationevidence.com/actions/488

## **Provide artificial nests (wildfowl — artificial/floating islands)**

Two studies from North America found that wildfowl used artificial islands and floating rafts and had high nesting success. A study in the UK found that wildfowl preferentially nested on vegetated rather than bare islands. *Assessment: likely to be beneficial (effectiveness 45%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/483

### **Unknown effectiveness (limited evidence)**

#### **Artificially incubate eggs or warm nests**

One of two studies found that no kakapo chicks or eggs died of cold when they were artificially warmed when females left the nest. A study from the UK found that great tits were less likely to interrupt their laying sequence if their nest boxes were warmed, but there was no effect on egg or clutch size. *Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 16%; harms 0%).*

#### **Guard nests**

We captured four studies describing the effects of guarding nests. One, from Costa Rica, found an increase in scarlet macaw population after nest monitoring and several other interventions. Two studies from Puerto Rico and New Zealand found that nest success was higher, or mortality lower, when nests were monitored. A study from New Zealand found that nest success was high overall when nests were monitored. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 24%; harms 0%).*

http://www.conservationevidence.com/actions/506

## **Provide artificial nests (gamebirds)**

A study in China found that approximately 40% of the local population of Cabot's tragopans used nesting platforms. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/484

#### **Provide artificial nests (grebes)**

A study from the UK found that grebes used nesting rafts in some areas but not others. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 9%; harms 0%).*

http://www.conservationevidence.com/actions/479

#### **Provide artificial nests (ibises and flamingos)**

A study from Turkey found that ibises moved to a site with artificial breeding ledges. A study from Spain and France found that large numbers of flamingos used artificial nesting islands. *Assessment: unknown effectiveness — limited evidence (effectiveness 42%; certainty 31%; harms 0%).*

http://www.conservationevidence.com/actions/487

#### **Provide artificial nests (parrots)**

A study from Costa Rica found that the local population of scarlet macaws increased following the installation of nest boxes along with several other interventions. Five studies from South and Central America and Mauritius found that nest boxes were used by several species of parrots. One study from Peru found that blue-and-yellow macaws only used modified palms, not 'boxes', whilst another study found that scarlet macaws used both PVC and wooden boxes. Four studies from Venezuela and Columbia found that several species rarely, if ever, used nest boxes. Six studies from Central and South America found that parrots nested successfully in nest boxes, with two species showing higher levels of recruitment into the population following nest box erection and another finding that success rates for artificial nests were similar to natural nests. Three studies from South America found that artificial nests had low success rates, in two cases due to poaching. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 38%; harms 11%).*

http://www.conservationevidence.com/actions/497

## **Provide artificial nests (pigeons)**

Two studies from the USA and the Netherlands found high use rates and high nesting success of pigeons and doves using artificial nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 16%; harms 0%).*

http://www.conservationevidence.com/actions/492

## **Provide artificial nests (rails)**

A study from the UK found that common moorhens and common coot readily used artificial nesting islands. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/485

## **Provide artificial nests (rollers)**

A study from Spain found that the use of nest boxes by rollers increased over time and varied between habitats. Another study from Spain found no difference in success rates between new and old nest boxes. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/494

### **Provide artificial nests (swifts)**

A study from the USA found that Vaux's swifts successfully used nest boxes provided. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 16%; harms 0%).*

#### **Provide artificial nests (trogons)**

A small study from Guatemala found that at least one resplendent quetzal nested in nest boxes provided. *Assessment: unknown effectiveness — limited evidence (effectiveness 19%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/493

## **Provide artificial nests (waders)**

Two studies from the USA and the UK found that waders used artificial islands and nesting sites. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/486

#### **Provide artificial nests (woodpeckers)**

Four studies from the USA found local increases in red-cockaded woodpecker populations or the successful colonisation of new areas following the installation of 'cavity inserts'. One study also found that the productivity of birds using the inserts was higher than the regional average. Two studies from the USA found that red-cockaded woodpeckers used cavity inserts, in one case more frequently than making their own holes or using natural cavities. One study from the USA found that woodpeckers roosted, but did not nest, in nest boxes. Five studies from the USA found that some woodpeckers excavated holes in artificial snags but only roosted in excavated holes or nest boxes. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 39%; harms 0%)*.

http://www.conservationevidence.com/actions/496

## **Provide nesting habitat for birds that is safe from extreme weather**

Two of three studies found that nesting success of waders and terns was no higher on raised areas of nesting substrate, with one finding that similar numbers were lost to flooding. The third study found that Chatham Island oystercatchers used raised nest platforms, but did not report on nesting success. *Assessment: unknown effectiveness — limited evidence (effectiveness 28%; certainty 23%; harms 0%).*

## **Provide nesting material for wild birds**

One of two studies found that wild birds took nesting material provided; the other found only very low rates of use. *Assessment: unknown effectiveness — limited evidence (effectiveness 11%; certainty 9%; harms 0%).*

http://www.conservationevidence.com/actions/501

## **Remove vegetation to create nesting areas**

Two out of six studies found increases in population sizes at seabird and wader colonies after vegetation was cleared and a third found that an entire colony moved to a new site that was cleared of vegetation. Two of these studies found that several interventions were used at once. Two studies found that gulls and terns used plots cleared of vegetation, one of these found that nesting densities were higher on partially-cleared plots than totally cleared, or uncleared, plots. One study found that tern nesting success was higher on plots after they were cleared of vegetation and other interventions were used. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 28%; harms 10%).*

http://www.conservationevidence.com/actions/505

## **Repair/support nests to support breeding**

A study from Puerto Rico found that no chicks died from chilling after nine nests were repaired to prevent water getting in. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/502

### **Use differently-coloured artificial nests**

A study from the USA found that two bird species (a thrush and a pigeon) both showed colour preferences for artificial nests, but that these preferences differed between species. In each case, clutches in the preferred colour nest were less successful than those in the other colour. *Assessment: unknown effectiveness — limited evidence (effectiveness 3%; certainty 9%; harms 0%).*

## 3.14.3 Foster chicks in the wild


## **Likely to be beneficial**

#### **Foster eggs or chicks with wild conspecifics (raptors)**

Ten out of 11 studies from across the world found that fostering raptor chicks to wild conspecifics had high success rates. A single study from the USA found that only one of six eggs fostered to wild eagle nests hatched and was raised. A study from Spain found that Spanish imperial eagle chicks were no more likely to survive to fledging if they were transferred to foster nests from three chick broods (at high risk from siblicide). A study from Spain found that young (15–20 day old) Montagu's harrier chicks were successfully adopted, but three older (27–29 day old) chicks were rejected. *Assessment: likely to be beneficial (effectiveness 70%; certainty 60%; harms 10%).*

http://www.conservationevidence.com/actions/510

## **Foster eggs or chicks with wild non-conspecifics (crossfostering) (songbirds)**

A study from the USA found that the survival of cross-fostered yellow warbler chicks was lower than previously-published rates for the species. A study from Norway found that the success of cross-fostering small songbirds varied depending on the species of chick and foster birds but recruitment was the same or higher than control chicks. The pairing success of cross-fostered chicks varied depending on species of chick and foster birds. *Assessment: likely to be beneficial (effectiveness 45%; certainty 45%; harms 10%).*

http://www.conservationevidence.com/actions/520

#### **Unknown effectiveness (limited evidence)**

### **Foster eggs or chicks with wild conspecifics (bustards)**

A small study in Saudi Arabia found that a captive-bred egg was successfully fostered to a female in the wild. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 5%; harms 0%).*

http://www.conservationevidence.com/actions/513

#### **Foster eggs or chicks with wild conspecifics (cranes)**

A small study in Canada found high rates of fledging for whooping crane eggs fostered to first time breeders. *Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/512

## **Foster eggs or chicks with wild conspecifics (gannets and boobies)**

A small study in Australia found that gannet chicks were lighter, and hatching and fledging success lower in nests which had an extra egg or chick added. However, overall productivity was non-significantly higher in experimental nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 9%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/507

#### **Foster eggs or chicks with wild conspecifics (owls)**

A study in the USA found high fledging rates for barn owl chicks fostered to wild pairs. A study from Canada found that captive-reared burrowing owl chicks fostered to wild nests did not have lower survival or growth rates than wild chicks. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/511

#### **Foster eggs or chicks with wild conspecifics (parrots)**

A study from Venezuela found that yellow-shouldered Amazon chicks had high fledging rates when fostered to conspecific nests in the wild. A second study from Venezuela found lower poaching rates of yellow-shouldered Amazons when chicks were moved to foster nests closer to a field base. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 14%; harms 0%).*

http://www.conservationevidence.com/actions/515

#### **Foster eggs or chicks with wild conspecifics (vultures)**

Two small studies in Italy and the USA found that single chicks were successfully adopted by foster conspecifics, although in one case this led to the death of one of the foster parents' chicks. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 15%; harms 41%).*

http://www.conservationevidence.com/actions/509

#### **Foster eggs or chicks with wild conspecifics (waders)**

Two small trials in North America found that piping plovers accepted chicks introduced into their broods, although in one case the chick died. A study from New Zealand found that survival of fostered black stilts was higher for birds fostered to conspecifics rather than a closely related species. *Assessment: unknown effectiveness — limited evidence (effectiveness 29%; certainty 9%; harms 0%).*

## **Foster eggs or chicks with wild conspecifics (woodpeckers)**

Three studies from the USA found that red-cockaded woodpecker chicks fostered to conspecifics had high fledging rates. One small study found that fostered chicks survived better than chicks translocated with their parents. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 29%; harms 0%).*

http://www.conservationevidence.com/actions/514

## **Foster eggs or chicks with wild non-conspecifics (crossfostering) (cranes)**

Two studies from the USA found low fledging success for cranes fostered to non-conspecifics' nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 14%; certainty 35%; harms 10%).*

http://www.conservationevidence.com/actions/519

### **Foster eggs or chicks with wild non-conspecifics (crossfostering) (ibises)**

A 2007 literature review describes attempting to foster northern bald ibis chicks with cattle egrets as unsuccessful. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/518

## **Foster eggs or chicks with wild non-conspecifics (crossfostering) (petrels and shearwaters)**

A study from Hawaii found that Newell's shearwater eggs fostered to wedge-tailed shearwater nests had high fledging rates. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 6%; harms 0%).*

http://www.conservationevidence.com/actions/516

## **Foster eggs or chicks with wild non-conspecifics (crossfostering) (waders)**

A study from the USA found that killdeer eggs incubated and raised by spotted sandpipers had similar fledging rates to parent-reared birds. A study from New Zealand found that cross-fostering black stilt chicks to black-winged stilt nests increased nest success, but cross-fostered chicks had lower success than chicks fostered to conspecifics' nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/517

## 3.14.4 Provide supplementary food



#### **Beneficial**

## **Provide supplementary food to increase adult survival (songbirds)**

Seven studies from Europe and the USA found higher densities or larger populations of songbird species in areas close to supplementary food. Six studies from Europe, Canada and Japan found that population trends or densities were no different between fed and unfed areas. Four studies from around the world found that birds had higher survival when supplied with supplementary food. However, in two studies this was only apparent in some individuals or species and one study from the USA found that birds with feeding stations in their territories had lower survival. Six studies from Europe and the USA found that birds supplied with supplementary food were in better physical condition than unfed birds. However, in four studies this was only true for some individuals, species or seasons. Two studies investigated the effect of feeding on behaviours: one in the USA found that male birds spent more time singing when supplied with food and one in Sweden found no behavioural differences between fed and unfed birds. Thirteen studies from the UK, Canada and the USA investigated use of feeders. Four studies from the USA and the UK found high use of supplementary food, with up to 21% of birds' daily energy needs coming from feeders. However, another UK study found very low use of food. The timing of peak feeder use varied. Two trials from the UK found that the use of feeders increased with distance to houses and decreased with distance to cover. Two studies in Canada and the UK, found that preferences for feeder locations and positions varies between species. *Assessment: beneficial (effectiveness 65%; certainty 75%; harms 0%).*

http://www.conservationevidence.com/actions/552

#### **Likely to be beneficial**

#### **Place feeders close to windows to reduce collisions**

A randomised, replicated and controlled study in the USA found that fewer birds hit windows, and fewer were killed, when feeders were placed close to windows, compared to when they were placed further away. *Assessment: likely to be beneficial (effectiveness 44%; certainty 43%; harms 0%).*

## **Provide calcium supplements to increase survival or reproductive success**

Eight of 13 studies (including a literature review) from across the world found some positive effects of calcium provisioning on birds' productivites (six studies) or health (two studies). Six studies (including the review) found no evidence for positive effects on some of the species studied. One study from Europe found that birds at polluted sites took more calcium supplement than those at cleaner sites. *Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/559

## **Provide supplementary food to increase adult survival (cranes)**

A study from Japan and a global literature review found that local crane populations increased after the provision of supplementary food. *Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 15%).*

http://www.conservationevidence.com/actions/547

## **Provide supplementary food to increase reproductive success (gulls, terns and skuas)**

Four studies of three experiments from Europe and Alaska found that providing supplementary food increased fledging success or chick survival in two gull species, although a study from the UK found that this was only true for one of two islands. One study from the Antarctic found no effect of feeding parent skuas on productivity. One study from Alaska found increased chick growth when parents were fed but a study from the Antarctic found no such increase. *Assessment: likely to be beneficial (effectiveness 42%; certainty 41%; harms 0%)*.

http://www.conservationevidence.com/actions/525

### **Provide supplementary food to increase reproductive success (owls)**

Two replicated, controlled trials from Europe and the USA found that owls supplied with supplementary food had higher hatching and fledging rates. The European study, but not the American, also found that fed pairs laid earlier and had larger clutches. The study in the USA also found that owls were no more likely to colonise nest boxes provided with supplementary food. *Assessment: likely to be beneficial (effectiveness 50%; certainty 42%; harms 0%).*

http://www.conservationevidence.com/actions/533

#### **Provide supplementary food to increase reproductive success (raptors)**

A small study in Italy described a small increase in local kite populations following the installation of a feeding station. Four European studies found that kestrels and Eurasian sparrowhawks laid earlier than control birds when supplied with supplementary food. Three studies from the USA and Europe found higher chick survival or condition when parents were supplied with food, whilst three from Europe found fed birds laid larger clutches and another found that fed male hen harriers bred with more females than control birds. Four studies from across the world found no evidence that feeding increased breeding frequency, clutch size, laying date, eggs size or hatching or fledging success. A study from Mauritius found uncertain effects of feeding on Mauritius kestrel reproduction. There was some evidence that the impact of feeding was lower in years with peak numbers of prey species. *Assessment: likely to be beneficial (effectiveness 55%; certainty 52%; harms 0%).*

http://www.conservationevidence.com/actions/532

#### **Provide supplementary food to increase reproductive success (songbirds)**

Two studies from the USA found evidence for higher population densities of magpies and American blackbirds in areas provided with supplementary food, whilst two studies from the UK and Canada found that population densities were not affected by feeding. Twelve studies from across the world found that productivity was higher for fed birds than controls. Eleven studies from Europe and the USA found that fed birds had the same, or even lower, productivity or chick survival than control birds. Nine studies from Europe and North America found that the eggs of fed birds were larger or heavier, or that the chicks of fed birds were in better physical condition. However, eight studies from across the world found no evidence for better condition or increased size in the eggs or chicks of fed birds. Six studies from across the world found that food-supplemented pairs laid larger clutches, whilst 14 studies from Europe and North America found that fed birds did not lay larger clutches. Fifteen studies from across the world found that birds supplied with supplementary food began nesting earlier than controls, although in two cases only certain individuals, or those in particular habitats, laid earlier. One study found that fed birds had shorter incubations than controls whilst another found that fed birds re-nested quicker and had shorter second incubations. Four studies from the USA and Europe found that fed birds did not lay any earlier than controls. Seven studies from across the world found that fed parent birds showed positive behavioural responses to feeding. However, three studies from across the world found neutral or negative responses to feeding. *Assessment: likely to be beneficial (effectiveness 51%; certainty 85%; harms 6%).*

http://www.conservationevidence.com/actions/537

#### **Unknown effectiveness (limited evidence)**

### **Provide perches to improve foraging success**

One of four studies, from Sweden, found that raptors used clearcuts provided with perches more than clearcuts without perches. Two studies found that birds used perches provided, but a controlled study from the USA found that shrikes did not alter foraging behaviour when perches were present. *Assessment: unknown effectiveness — limited evidence (effectiveness 45%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/556

## **Provide supplementary food through the establishment of food populations**

One of four studies that established prey populations found that wildfowl fed on specially-planted rye grass. Two studies found that cranes in the USA and owls in Canada did not respond to established prey populations. A study from Sweden found that attempts to increase macroinvertebrate numbers for wildfowl did not succeed. *Assessment: unknown effectiveness — limited evidence (effectiveness 9%; certainty 26%; harms 0%)..*

## **Provide supplementary food to allow the rescue of a second chick**

A study from Spain found that second chicks from lammergeier nests survived longer if nests were provided with food, in one case allowing a chick to be rescued. *Assessment: unknown effectiveness — limited evidence (effectiveness 15%; certainty 14%; harms 0%).*

http://www.conservationevidence.com/actions/541

## **Provide supplementary food to increase adult survival (gamebirds)**

Two European studies found increased numbers of birds in fed areas, compared to unfed areas. There was only an increase in the overall population in the study area in one of these studies. Of four studies in the USA on northern bobwhites, one found that birds had higher overwinter survival in fed areas, one found lower survival, one found fed birds had higher body fat percentages and a literature review found no overall effect of feeding. *Assessment: unknown effectiveness — limited evidence (effectiveness 49%; certainty 38%; harms 0%).*

http://www.conservationevidence.com/actions/544

## **Provide supplementary food to increase adult survival (gulls, terns and skuas)**

A study in the Antarctic found that fed female south polar skuas lost more weight whilst feeding two chicks than unfed birds. There was no difference for birds with single chicks, or male birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 20%; harms 10%).*

http://www.conservationevidence.com/actions/548

### **Provide supplementary food to increase adult survival (hummingbirds)**

Four studies from the USA found that three species of hummingbird preferred higher concentrations of sucrose, consuming more and visiting feeders more frequently. A study from the USA found that hummingbirds preferentially fed on sugar solutions over artificial sweeteners, and that the viscosity of these solutions did not affect their consumption. Two studies from Mexico and Argentina found that four species showed preferences for

#### *Bird Conservation*

sucrose over fructose or glucose and sucrose over a sucrose-glucose mix, but no preference for sucrose over a glucose-fructose mix. A study from the USA found that birds showed a preference for red-dyed sugar solutions over five other colours. A study from the USA found that rufous hummingbirds preferentially fed on feeders that were placed higher. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 24%; harms 0%).*

http://www.conservationevidence.com/actions/550

## **Provide supplementary food to increase adult survival (nectar-feeding songbirds)**

Two studies from Australia and New Zealand found that ten species of honeyeaters and stitchbirds readily used feeders supplying sugar solutions, with seasonal variations varying between species. A series of *ex situ* trials using southern African birds found that most species preferred sucrose solutions over glucose or fructose. One study found that sunbirds and sugarbirds only showed such a preference at low concentrations. Two studies found that two species showed preferences for sucrose when comparing 20% solutions, although a third species did not show this preference. All species rejected solutions with xylose added. A final study found that sucrose preferences were only apparent at equicalorific concentrations high enough for birds to subsist on. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/553

### **Provide supplementary food to increase adult survival (pigeons)**

The first of two studies of a recently-released pink pigeon population on Mauritius found that fewer than half the birds took supplementary food. However, the later study found that almost all birds used supplementary feeders. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 19%; harms 0%).*

http://www.conservationevidence.com/actions/549

## **Provide supplementary food to increase adult survival (raptors)**

Two studies in the USA found that nesting northern goshawks were significantly heavier in territories supplied with supplementary food, compared with those from unfed territories. *Assessment: unknown effectiveness— limited evidence (effectiveness 30%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/546

## **Provide supplementary food to increase adult survival (vultures)**

A study from Spain found a large increase in griffon vulture population in the study area following multiple interventions including supplementary feeding. Two studies from the USA and Israel found that vultures fed on the carcasses provided for them. In the study in Israel vultures were sometimes dominated by larger species at a feeding station supplied twice a month, but not at one supplied every day. *Assessment: unknown effectiveness — limited evidence (effectiveness 18%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/545

## **Provide supplementary food to increase adult survival (waders)**

A study in Northern Ireland found that waders fed on millet seed when provided, but were dominated by other ducks when larger seeds were provided. *Assessment: unknown effectiveness — limited evidence (effectiveness 22%; certainty 9%; harms 0%).*

http://www.conservationevidence.com/actions/543

## **Provide supplementary food to increase adult survival (wildfowl)**

Two studies from Canada and Northern Ireland found that five species of wildfowl readily consumed supplementary grains and seeds. The Canadian study found that fed birds were heavier and had larger hearts or flight muscles or more body fat than controls. *Assessment: unknown effectiveness — limited evidence (effectiveness 14%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/542

## **Provide supplementary food to increase adult survival (woodpeckers)**

One replicated, controlled study from the USA found that 12 downy woodpeckers supplied with supplementary food had higher nutritional

#### *Bird Conservation*

statuses than unfed birds. However, two analyses of a replicated, controlled study of 378 downy woodpeckers from the USA found that they did not have higher survival rates or nutritional statuses than unfed birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 30%; harms 0%).*

http://www.conservationevidence.com/actions/551

## **Provide supplementary food to increase reproductive success (auks)**

Two replicated studies from the UK found that Atlantic puffin chicks provided with supplementary food were significantly heavier than control chicks, but fed chicks fledged at the same time as controls. A randomised, replicated and controlled study from Canada found that tufted puffin chicks supplied with supplementary food fledged later than controls and that fed chicks had faster growth by some, but not all, metrics. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 38%; harms 0%).*

http://www.conservationevidence.com/actions/524

## **Provide supplementary food to increase reproductive success (gamebirds)**

A controlled study in Tibet found that Tibetan eared pheasants fed supplementary food laid significantly larger eggs and clutches than control birds. Nesting success and laying dates were not affected. *Assessment: unknown effectiveness — limited evidence (effectiveness 23%; certainty 10%; harms 0%)*.

http://www.conservationevidence.com/actions/527

## **Provide supplementary food to increase reproductive success (gannets and boobies)**

A small controlled study in Australia found that Australasian gannet chicks were significantly heavier if they were supplied with supplementary food, but only in one of two years. Fledging success of fed nests was also higher, but not significantly so. A randomised replicated and controlled study in the Galapagos Islands found that fed female Nazca boobies were more likely to produce two-egg clutches, and that second eggs were significantly heavier. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/523

## **Provide supplementary food to increase reproductive success (ibises)**

A study from China found that breeding success of crested ibis was correlated with the amount of supplementary food provided, although no comparison was made with unfed nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/530

## **Provide supplementary food to increase reproductive success (kingfishers)**

A controlled study in the USA found that belted kingfishers supplied with food had heavier nestlings and were more likely to renest. There was mixed evidence for the effect of feeding on laying date. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/534

## **Provide supplementary food to increase reproductive success (parrots)**

Two studies from New Zealand found evidence that providing supplementary food for kakapos increased the number of breeding attempts made, whilst a third study found that birds provided with specially-formulated pellets appeared to have larger clutches than those fed on nuts. One study found no evidence that providing food increased the number of nesting attempts. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 11%; harms 0%).*

http://www.conservationevidence.com/actions/536

## **Provide supplementary food to increase reproductive success (petrels)**

A replicated controlled study in Australia found that Gould's petrel chicks provided with supplementary food had similar fledging rates to both control and hand-reared birds, but were significantly heavier than other birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 19%; certainty 14%; harms 0%).*

http://www.conservationevidence.com/actions/522

## **Provide supplementary food to increase reproductive success (pigeons)**

A study in the UK found no differences in reproductive parameters of European turtle doves between years when food was supplied and those when it was not. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/535

## **Provide supplementary food to increase reproductive success (rails and coots)**

A small trial in the USA found that fed American coots laid heavier eggs, but not larger clutches, than controls. However, a randomised, replicated and controlled study in Canada found that clutch size, but not egg size, was larger in fed American coot territories. The Canadian study also found that coots laid earlier when fed, whilst a replicated trial from the UK found there was a shorter interval between common moorhens clutches in fed territories, but that fed birds were no more likely to produce second broods. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 26%; harms 0%).*

http://www.conservationevidence.com/actions/528

### **Provide supplementary food to increase reproductive success (vultures)**

Two studies from the USA and Greece found that there were local increases in two vulture populations following the provision of food in the area. A study from Israel found that a small, regularly supplied feeding station could provide sufficient food for breeding Egyptian vultures. A study from Italy found that a small population of Egyptian vultures declined following the provision of food, and only a single vulture was seen at the feeding station. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 24%; harms 0%).*

## **Provide supplementary food to increase reproductive success (waders)**

A small controlled trial from the Netherlands found that Eurasian oystercatchers did not produce larger replacement eggs if provided with supplementary food. Instead their eggs were smaller than the first clutch, whereas control females laid larger replacement eggs. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/529

## **Provide supplementary food to increase reproductive success (wildfowl)**

A small randomised controlled *ex situ* study from Canada found faster growth and higher weights for fed greater snow goose chicks than unfed ones, but no differences in mortality rates. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/526

### **Provide supplementary water to increase survival or reproductive success**

A controlled study from Morocco found that northern bald ibises provided with supplementary water had higher reproductive success than those a long way from water sources. *Assessment: unknown effectiveness — limited evidence (effectiveness 43%; certainty 14%; harms 0%).*

http://www.conservationevidence.com/actions/558

## 3.14.5 Translocations



#### **Beneficial**

## **Translocate birds to re-establish populations or increase genetic variation (birds in general)**

A review of 239 bird translocation programmes found 63–67% resulted in establishment of a self-sustaining population. *Assessment: beneficial (effectiveness 64%; certainty 65%; harms 0%).*

http://www.conservationevidence.com/actions/566

#### **Translocate birds to re-establish populations or increase genetic variation (raptors)**

Six studies of three translocation programmes in the UK and the USA found that all successfully established populations of white-tailed eagles, red kites and ospreys. A study in Spain found high survival of translocated Montagu's harrier fledglings. *Assessment: beneficial (effectiveness 65%; certainty 66%; harms 0%).*

http://www.conservationevidence.com/actions/574

#### **Likely to be beneficial**

#### **Translocate birds to re-establish populations or increase genetic variation (parrots)**

Three studies of two translocation programmes from the Pacific and New Zealand found that populations of parrots successfully established on islands after translocation. Survival of translocated birds ranged from 41% to 98% globally. Despite high survival, translocated kakapos in New Zealand had very low reproductive output. *Assessment: likely to be beneficial (effectiveness 50%; certainty 60%; harms 10%).*

http://www.conservationevidence.com/actions/578

#### **Translocate birds to re-establish populations or increase genetic variation (pelicans)**

Two reviews of a pelican translocation programme in the USA found high survival of translocated nestlings and rapid target population growth. Some growth may have been due to additional immigration from the source populations. *Assessment: likely to be beneficial (effectiveness 55%; certainty 49%; harms 0%).*

http://www.conservationevidence.com/actions/569

## **Translocate birds to re-establish populations or increase genetic variation (petrels and shearwaters)**

Three studies from Australia and New Zealand found that colonies of burrow-nesting petrels and shearwaters were successfully established following the translocation and hand-rearing of chicks. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/568

## **Translocate birds to re-establish populations or increase genetic variation (rails)**

Three studies of two translocation programmes in the Seychelles and New Zealand found high survival rates among translocated rail. All three studies round that the birds bred successfully. *Assessment: likely to be beneficial (effectiveness 54%; certainty 44%; harms 14%).*

http://www.conservationevidence.com/actions/573

## **Translocate birds to re-establish populations or increase genetic variation (songbirds)**

Nine studies from across the world, including a review of 31 translocation attempts, found that translocations led to the establishment of songbird populations. Eight studies were on islands. Three studies reported on translocations that failed to establish populations. One study found nesting success decreased as the latitudinal difference between source area and release site increased. *Assessment: likely to be beneficial (effectiveness 50%; certainty 68%; harms 0%).*

http://www.conservationevidence.com/actions/580

## **Translocate birds to re-establish populations or increase genetic variation (wildfowl)**

Three studies of two duck translocation programmes in New Zealand and Hawaii found high survival, breeding and successful establishment of new populations. However a study in the USA found that no ducks stayed at the release site and there was high mortality after release. A study in the USA found wing-clipping prevented female ducks from abandoning their ducklings. *Assessment: likely to be beneficial (effectiveness 42%; certainty 50%; harms 19%).*

http://www.conservationevidence.com/actions/571

## **Translocate birds to re-establish populations or increase genetic variation (woodpeckers)**

Six studies of four programmes found that >50% translocated birds remained at their new sites, and two studies reported large population increases. Birds from four programmes were reported as forming pairs or breeding and one study round translocated nestlings fledged at similar rates to native chicks. All studies were of red-cockaded woodpeckers. *Assessment: likely to be beneficial (effectiveness 51%; certainty 42%; harms 0%).*

http://www.conservationevidence.com/actions/577

#### **Use decoys to attract birds to new sites**

Ten studies found that birds nested in areas where decoys were placed or that more birds landed in areas with decoys than control areas. Six studies used multiple interventions at once. One study found that threedimensional models appeared more effective than two-dimensional ones, and that plastic models were more effective than rag decoys. *Assessment: likely to be beneficial (effectiveness 51%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/586

## **Use techniques to increase the survival of species after capture**

A study from the USA found that providing dark, quiet environments with readily-available food and water increased the survival of small songbirds after capture and the probability that they would adapt to captivity. A study from the USA found that keeping birds warm during transit increased survival. *Assessment: likely to be beneficial (effectiveness 49%; certainty 41%; harms 0%).*

#### **Use vocalisations to attract birds to new sites**

Seven out of ten studies from around the world found that seabirds were more likely to nest or land to areas where vocalisations were played, or moved to new nesting areas after vocalisations were played. Four of these studied multiple interventions at once. Three studies found that birds were no more likely to nest or land in areas where vocalisations were played. *Assessment: likely to be beneficial (effectiveness 45%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/585

#### **Trade-off between benefit and harms**

### **Translocate birds to re-establish populations or increase genetic variation (gamebirds)**

Three studies from the USA found that translocation of gamebirds led to population establishment or growth or an increase in lekking sites. Four studies from the USA found that translocated birds had high survival, but two found high mortality in translocated birds. Four studies from the USA found breeding rates among translocated birds were high or similar to resident birds. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 47%; harms 35%).*

http://www.conservationevidence.com/actions/572

#### **Unknown effectiveness (limited evidence)**

#### **Alter habitats to encourage birds to leave**

A study from Canada found that an entire Caspian tern population moved after habitat was altered at the old colony site, alongside several other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/587

## **Ensure translocated birds are familiar with each other before release**

Two studies from New Zealand found no evidence that ensuring birds were familiar with each other increased translocation success. *Assessment:*  *unknown effectiveness — limited evidence (effectiveness 0%; certainty 33%; harms 0%).*

http://www.conservationevidence.com/actions/582

#### **Translocate birds to re-establish populations or increase genetic variation (auks)**

A study in the USA and Canada found that 20% of translocated Atlantic puffins remained in or near the release site, with up to 7% breeding. *Assessment: unknown effectiveness — limited evidence (effectiveness 36%; certainty 38%; harms 0%).*

http://www.conservationevidence.com/actions/570

## **Translocate birds to re-establish populations or increase genetic variation (herons, storks and ibises)**

A study in the USA found that a colony of black-crowned night herons was successfully translocated and bred the year after translocation. *Assessment: unknown effectiveness — limited evidence (effectiveness 44%; certainty 3%; harms 0%).*

http://www.conservationevidence.com/actions/575

### **Translocate birds to re-establish populations or increase genetic variation (megapodes)**

A study from Indonesia found that up to 78% maleo eggs hatched after translocation. *Assessment: unknown effectiveness — limited evidence (effectiveness 49%; certainty 29%; harms 0%).*

http://www.conservationevidence.com/actions/567

#### **Translocate birds to re-establish populations or increase genetic variation (owls)**

A small study from New Zealand found that translocating two male boobooks allowed the establishment of a population when they interbred with a Norfolk Island boobook. A study in the USA found high survival amongst burrowing owls translocated as juveniles, although birds were not seen after release. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 19%; harms 0%).*

## **Translocate nests to avoid disturbance**

All five studies captured found some success in relocating nests while they were in use, but one found that fewer than half of the burrowing owls studied were moved successfully; a study found that repeated disturbance caused American kestrels to abandon their nest and a study found that one barn swallow abandoned its nest after it was moved. *Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 39%; harms 30%).*

http://www.conservationevidence.com/actions/584

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Ensure genetic variation to increase translocation success.

# 3.15 Captive breeding, rearing and releases (*ex situ* conservation)

## 3.15.1 Captive breeding



#### **Likely to be beneficial**

## **Artificially incubate and hand-rear birds in captivity (raptors)**

Six studies from across the world found high success rates for artificial incubation and hand-rearing of raptors. A replicated and controlled study from France found that artificially incubated raptor eggs had lower hatching success than parent-incubated eggs but fledging success for handreared chicks was similar to wild chicks. A study from Canada found that hand-reared chicks had slower growth and attained a lower weight than parent-reared birds. A replicated study from Mauritius found that handrearing of wild eggs had higher success than hand-rearing captive-bred chicks. Three studies that provided methodological comparisons reported that incubation temperature affected hatching success and adding saline to the diet of falcon chicks increased their weight gain. *Assessment: likely to be beneficial (effectiveness 60%; certainty 52%; harms 5%).*

http://www.conservationevidence.com/actions/614

#### **Artificially incubate and hand-rear birds in captivity (seabirds)**

Five studies from across the world found evidence for the success of hand-rearing seabirds. One small study in Spain found that one of five hand-reared Audouin's gulls successfully bred in the wild. Four studies found that various petrel species successfully fledged after hand-rearing. One controlled study found that fledging rates of hand-reared birds was similar to parent-reared birds, although a study on a single bird found that the chick fledged at a lower weight and later than parent-reared chicks. *Assessment: likely to be beneficial (effectiveness 67%; certainty 45%; harms 2%).*

http://www.conservationevidence.com/actions/604

### **Artificially incubate and hand-rear birds in captivity (songbirds)**

Four studies from the USA found high rates of success for artificial incubation and hand-rearing of songbirds. One study found that crow chicks fed more food had higher growth rates, but these rates never matched those of wild birds. *Assessment: likely to be beneficial (effectiveness 51%; certainty 44%; harms 1%).*

http://www.conservationevidence.com/actions/616

## **Artificially incubate and hand-rear birds in captivity (waders)**

Three out of four replicated and controlled studies from the USA and New Zealand found that artificially incubated and/or hand-reared waders had higher hatching and fledging success than controls. One study from New Zealand found that hatching success of black stilt was lower for artificiallyincubated eggs. *Assessment: likely to be beneficial (effectiveness 64%; certainty 41%; harms 4%).*

http://www.conservationevidence.com/actions/611

### **Use captive breeding to increase or maintain populations (raptors)**

Three small studies and a review from around the world found that raptors bred successfully in captivity. Two of these studies found that wild-caught birds bred in captivity after a few years, with one pair of brown goshawks producing 15 young over four years, whilst a study on bald eagle captive breeding found low fertility in captive-bred eggs, but that birds still produced chicks after a year. A review of Mauritius kestrel captive breeding found that 139 independent young were raised over 12 years from 30 eggs and chicks taken from the wild. An update of the same programme found that hand-reared Mauritius kestrels were less successful if they came from captive-bred eggs compared to wild 'harvested' eggs. *Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 10%).*

http://www.conservationevidence.com/actions/596

#### **Unknown effectiveness (limited evidence)**

## **Artificially incubate and hand-rear birds in captivity (bustards)**

Two reviews of a houbara bustard captive breeding programme in Saudi Arabia found no difference in survival between artificially and parentally incubated eggs, and that removing eggs from clutches as they were laid increased the number laid by females. *Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/610

## **Artificially incubate and hand-rear birds in captivity (cranes)**

Two studies from the USA found that hand-reared birds showed normal reproductive behaviour and higher survival than parent-reared birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 76%; certainty 31%; harms 0%).*

http://www.conservationevidence.com/actions/609

## **Artificially incubate and hand-rear birds in captivity (gamebirds)**

A study in Finland found that hand-reared grey partridges did not take off to fly as effectively as wild-caught birds, potentially making them more vulnerable to predation. *Assessment: unknown effectiveness — limited evidence (effectiveness 11%; certainty 10%; harms 50%).*

http://www.conservationevidence.com/actions/607

## **Artificially incubate and hand-rear birds in captivity (parrots)**

Two studies from South America describe the successful hand-rearing of parrot chicks. A review of the kakapo management programme found that chicks could be successfully raised and released, but that eggs incubated from a young age had low success. A study from the USA found that all hand-reared thick-billed parrots died within a month of release: significantly lower survival than for wild-caught birds translocated to the release site. *Assessment: unknown effectiveness — limited evidence (effectiveness 19%; certainty 30%; harms 11%).*

http://www.conservationevidence.com/actions/615

## **Artificially incubate and hand-rear birds in captivity (penguins)**

Two replicated and controlled studies from South Africa found that handreared and released African penguins had similar survival and breeding success as birds which were not hand-reared. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/605

## **Artificially incubate and hand-rear birds in captivity (rails)**

A controlled study from New Zealand found that post-release survival of hand-reared takahe was as high as wild-reared birds and that six of ten released females raised chicks. *Assessment: unknown effectiveness — limited evidence (effectiveness 64%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/608

## **Artificially incubate and hand-rear birds in captivity (storks and ibises)**

A small study in the USA describes the successful artificial incubation and hand-rearing of two Abdim's stork chicks, whilst a review of northern bald ibis conservation found that only very intensive rearing of a small number of chicks appeared to allow strong bonds, thought to be important for the successful release of birds into the wild, to form between chicks. *Assessment: unknown effectiveness — limited evidence (effectiveness 18%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/612

## **Artificially incubate and hand-rear birds in captivity (vultures)**

A study in Peru found that hand-reared Andean condors had similar survival to parent-reared birds after release into the wild. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/613

## **Artificially incubate and hand-rear birds in captivity (wildfowl)**

Two studies in Canada and India found high success rates for hand-rearing buffleheads and bar-headed geese in captivity. Eggs were artificially incubated or incubated under foster parents. A replicated, controlled study in England found that Hawaiian geese (nene) chicks showed less well-adapted behaviours if they were raised without parental contact. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 10%).*

http://www.conservationevidence.com/actions/606

#### **Freeze semen for artificial insemination**

Two small trials from the USA found that using thawed frozen semen for artificial insemination resulted in low fertility rates. A small trial from the USA found that a cryprotectant increased fertility rates achieved using frozen semen. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%; harms 45%).*

http://www.conservationevidence.com/actions/602

#### **Use artificial insemination in captive breeding**

A replicated study from Saudi Arabia found that artificial insemination could increase fertility in houbara bustards. A study of the same programme and a review found that repeated inseminations increased fertility, with the review arguing that artificial insemination had the potential to be a useful technique. Two studies from the USA found that artificially-inseminated raptors had either zero fertility, or approximately 50%. *Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/601

## **Use captive breeding to increase or maintain populations (bustards)**

Four studies of a captive breeding programme in Saudi Arabia reported that the houbara bustard chicks were successfully raised in captivity, with 285 chicks hatched in the 7th year of the project after 232 birds were used to start the captive population. Captive birds bred earlier and appeared to lay more eggs than wild birds. Forty-six percent of captive eggs hatched and 43% of chicks survived to ten years old. *Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 16%; harms 5%).*

## **Use captive breeding to increase or maintain populations (cranes)**

A study from Canada over 32 years found that whooping cranes successfully bred in captivity eight years after the first eggs were removed from the wild. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 17%; harms 6%).*

http://www.conservationevidence.com/actions/591

## **Use captive breeding to increase or maintain populations (pigeons)**

A review of a captive-breeding programme on Mauritius and in the UK found that 42 pink pigeons were successfully bred in captivity. *Assessment: unknown effectiveness — limited evidence (effectiveness 69%; certainty 21%; harms 0%).*

http://www.conservationevidence.com/actions/597

## **Use captive breeding to increase or maintain populations (rails)**

A study from Australia found that three pairs of Lord Howe Islandwoodhens successfully bred in captivity, with 66 chicks being produced over four years. *Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 11%; harms 5%).*

http://www.conservationevidence.com/actions/590

## **Use captive breeding to increase or maintain populations (seabirds)**

A study from Spain found that a single pair of Audouin's gulls successfully bred in captivity. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 4%; harms 5%).*

http://www.conservationevidence.com/actions/589

## **Use captive breeding to increase or maintain populations (songbirds)**

Three studies from Australia and the USA found that three species of songbird bred successfully in captivity. Four out of five pairs of wild-bred, hand-reared puaiohi formed pairs and laid a total of 39 eggs and a breeding population of helmeted honeyeaters was successfully established through a breeding programme. Only one pair of loggerhead shrikes formed pairs from eight wild birds caught and their first clutch died. *Assessment: unknown effectiveness — limited evidence (effectiveness 77%; certainty 31%; harms 5%).*

http://www.conservationevidence.com/actions/598

## **Use captive breeding to increase or maintain populations (storks and ibises)**

We captured a small study and a review both from the USA describing the captive breeding of storks. The study found that a pair bred; the review found that only seven of 19 species had been successfully bred in captivity. A review of bald ibis conservation found that 1,150 birds had been produced in captivity from 150 founders over 20 years. However, some projects had failed, and a study from Turkey found that captive birds had lower productivity than wild birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 30%; harms 8%).*

http://www.conservationevidence.com/actions/595

## **Use captive breeding to increase or maintain populations (tinamous)**

A replicated study from Costa Rica found that great tinamous successfully bred in captivity, with similar reproductive success to wild birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 15%; harms 5%).*

http://www.conservationevidence.com/actions/588

#### **Use puppets to increase the success of hand-rearing**

Three studies from the USA and Saudi Arabia found that crows and bustards raised using puppets did not have higher survival, dispersal or growth than chicks hand-reared conventionally. *Assessment: unknown effectiveness — limited evidence (effectiveness 4%; certainty 20%; harms 0%).*

## **Wash contaminated semen and use it for artificial insemination**

A replicated, controlled study from Spain found that washed, contaminated semen could be used to successfully inseminate raptors. *Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/603

#### **Evidence not assessed**

## **Can captive breeding have deleterious effects?**

We captured no studies investigating the effects of captive-breeding on fitness. Three studies using wild and captive populations or museum specimens found physiological or genetic changes in populations that had been bred in captivity. One found that changes were more likely to be caused by extremely low population levels than by captivity.

http://www.conservationevidence.com/actions/599

## 3.15.2 Release captive-bred individuals



## **Likely to be beneficial**

#### **Provide supplementary food after release**

All three studies captured found that released birds used supplementary food provided. One study from Australia found that malleefowl had higher survival when provided with food and a study from Peru found that supplementary food could be used to increase the foraging ranges of Andean condors after release. *Assessment: likely to be beneficial (effectiveness 45%; certainty 48%; harms 0%).*

## **Release captive-bred individuals into the wild to restore or augment wild populations (cranes)**

Four studies of five release programmes from the USA and Russia found that released cranes had high survival or bred in the wild. Two studies from two release programmes in the USA found low survival of captivebred eggs fostered to wild birds compared with wild eggs, or a failure to increase the wild flock size. A worldwide review found that releases of migratory species were more successful if birds were released into existing flocks, and for non-migratory populations. One study from the USA found that birds released as sub-adults had higher survival than birds crossfostered to wild birds. *Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 5%).*

http://www.conservationevidence.com/actions/621

## **Release captive-bred individuals into the wild to restore or augment wild populations (raptors)**

Five studies of three release programmes from across the world found the establishment or increase of wild populations of falcons. Five studies from the USA found high survival of released raptors although one study from Australia found that a wedge-tailed eagle had to be taken back into captivity after acting aggressively towards humans, and another Australian study found that only one of 15 brown goshawks released was recovered. *Assessment: likely to be beneficial (effectiveness 69%; certainty 56%; harms 10%).*

http://www.conservationevidence.com/actions/626

## **Release captive-bred individuals into the wild to restore or augment wild populations (songbirds)**

A study in Mauritius describes the establishment of a population of Mauritius fody following the release of captive-bred individuals. Four studies of three release programmes on Hawaii found high survival of all three species released, with two thrush species successfully breeding. A replicated, controlled study from the USA found that shrike pairs with captive-bred females had lower reproductive success than pairs where both parents were wild-bred. *Assessment: likely to be beneficial (effectiveness 42%; certainty 40%; harms 5%).*

### **Release captive-bred individuals into the wild to restore or augment wild populations (vultures)**

Four studies of two release programmes found that release programmes led to large population increases in Andean condors in Colombia and griffon vultures in France. A small study in Peru found high survival of released Andean condors over 18 months, with all fatalities occurring in the first six months after release. *Assessment: likely to be beneficial (effectiveness 73%; certainty 54%; harms 0%).*

http://www.conservationevidence.com/actions/625

#### **Unknown effectiveness (limited evidence)**

#### **Clip birds' wings on release**

Two of four studies found that bustards and geese had lower survival when released into holding pens with clipped wings compared to birds released without clipped wings. One study found no differences in survival for clipped or unclipped northern bald ibis. One study found that adult geese released with clipped wings survived better than geese released before they were able to fly. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 30%; harms 5%).*

http://www.conservationevidence.com/actions/633

#### **Release birds as adults or sub-adults not juveniles**

Three out of nine studies from across the world found that birds released as sub-adults had higher survival than those released as juveniles. Two studies found lower survival of wing-clipped sub-adult geese and bustards, compared with juveniles and one study found lower survival of all birds released as sub-adults, compared to those released as juveniles. Three studies found no differences in survival for birds released at different ages, although one found higher reproduction in birds released at greater ages. *Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 15%; harms 19%).*

#### **Release birds in groups**

A study from New Zealand found that released stilts were more likely to move long distances after release if they were released in larger groups. *Assessment: unknown effectiveness — limited evidence (effectiveness 32%; certainty 26%; harms 2%).*

http://www.conservationevidence.com/actions/634

## **Release captive-bred individuals into the wild to restore or augment wild populations (bustards)**

Three reviews of a release programme for houbara bustard in Saudi Arabia found low initial survival of released birds, but the establishment of a breeding population and an overall success rate of 41%. The programme tested many different release techniques, the most successful of which was release of sub-adults, which were able to fly, into a large exclosure. *Assessment: unknown effectiveness — limited evidence (effectiveness 34%; certainty 26%; harms 5%).*

http://www.conservationevidence.com/actions/622

#### **Release captive-bred individuals into the wild to restore or augment wild populations (gamebirds)**

One of five studies from across the world found that releasing gamebirds established a population or bolstered an existing population. A review of a reintroduction programme in Pakistan found some breeding success in released cheer pheasants, but habitat change at the release site then excluded released birds. Three studies from Europe and the USA found that released birds had low survival, low reproductive success and no impact on the wild population. *Assessment: unknown effectiveness — limited evidence (effectiveness 5%; certainty 35%; harms 1%).*

http://www.conservationevidence.com/actions/619

### **Release captive-bred individuals into the wild to restore or augment wild populations (owls)**

A study in the USA found that a barn owl population was established following the release of 157 birds in the area over three years. A replicated, controlled study in Canada found that released burrowing owls had similar reproductive output but higher mortality than wild birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 15%; harms 0%).*

http://www.conservationevidence.com/actions/627

## **Release captive-bred individuals into the wild to restore or augment wild populations (parrots)**

A study from Venezuela found that the population of yellow-shouldered amazons increased significantly following the release of captive-bred birds along with other interventions. A study in Costa Rica and Peru found high survival and some breeding of scarlet macaw after release. Three replicated studies in the USA, Dominican Republic and Puerto Rico found low survival in released birds, although the Puerto Rican study also found that released birds bred successfully. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 3%).*

http://www.conservationevidence.com/actions/629

#### **Release captive-bred individuals into the wild to restore or augment wild populations (pigeons)**

A single review of a captive-release programme in Mauritius found that that released pink pigeons had a first year survival of 36%. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 5%; harms 1%).*

http://www.conservationevidence.com/actions/628

#### **Release captive-bred individuals into the wild to restore or augment wild populations (rails)**

One study from Australia found that released Lord Howe Island woodhens successfully bred in the wild, re-establishing a wild population and a study from the UK found high survival of released corncrake in the first summer after release. A replicated study in New Zealand found very low survival of North Island weka following release, mainly due to predation. *Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 16%; harms 0%).*

## **Release captive-bred individuals into the wild to restore or augment wild populations (storks and ibises)**

A replicated study and a review of northern bald ibis release programmes in Europe and the Middle East found that only one of four resulted in a wild population being established or supported, with many birds dying or dispersing, rather than forming stable colonies. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 20%; harms 2%).*

http://www.conservationevidence.com/actions/624

## **Release captive-bred individuals into the wild to restore or augment wild populations (waders)**

A review of black stilt releases in New Zealand found that birds had low survival (13–20%) and many moved away from their release sites. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 5%; harms 15%).*

http://www.conservationevidence.com/actions/623

## **Release captive-bred individuals into the wild to restore or augment wild populations (wildfowl)**

Two studies of reintroduction programmes of ducks in New Zealand found high survival of released birds and population establishment. A study from Alaska found low survival of released cackling geese, but the population recovered from 1,000 to 6,000 birds after releases and the control of mammalian predators. A review of a reintroduction programme from Hawaii found that the release of Hawaiian geese (nene) did not result in the establishment of a self-sustaining population. Two studies from Canada found very low return rates for released ducks with one finding no evidence for survival of released birds over two years, although there was some evidence that breeding success was higher for released birds than wild ones. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 24%; harms 0%).*

http://www.conservationevidence.com/actions/618

### **Release chicks and adults in 'coveys'**

Two out of three studies found that geese and partridges released in coveys had higher survival than young birds released on their own or adults released in pairs. A study from Saudi Arabia found that bustard chicks had low survival when released in coveys with flightless females. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 36%; harms 6%).*

http://www.conservationevidence.com/actions/635

### **Use 'anti-predator training' to improve survival after release**

Both studies captured found higher survival for birds given predator training before release, compared with un-trained birds. One found that using a live fox, but not a model, for training increased survival in bustards, but that several birds were injured during training. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 9%).*

http://www.conservationevidence.com/actions/637

#### **Use appropriate populations to source released populations**

Two studies from Europe found that birds from populations near release sites adapted better and in one case had higher reproductive productivity than those from more distant populations. *Assessment: unknown effectiveness limited evidence (effectiveness 53%; certainty 31%; harms 0%).*

http://www.conservationevidence.com/actions/631

#### **Use 'flying training' before release**

A study from the Dominican Republic found that parrots had higher firstyear survival if they were given pre-release flying training. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/638

#### **Use holding pens at release sites**

Three of four studies from North America and Saudi Arabia found that birds released into holding pens were more likely to form pairs or had higher survival than birds released into the open. One study found that parrots released into pens had lower survival than those released without preparation. A review of northern bald ibis releases found that holding pens could be used to prevent birds from migrating from the release site and so increase survival. *Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 36%; harms 2%).*

http://www.conservationevidence.com/actions/632

## **Use microlites to help birds migrate**

A study from Europe found that northern bald ibises followed a microlite south in the winter but failed to make the return journey the next year. *Assessment: unknown effectiveness — limited evidence (effectiveness 3%; certainty 5%; harms 5%).*

# 4. FARMLAND CONSERVATION

**Lynn V. Dicks, Joscelyne E. Ashpole, Juliana Dänhardt, Katy James, Annelie Jönsson, Nicola Randall, David A. Showler, Rebecca K. Smith, Susan Turpie, David R. Williams & William J. Sutherland**

**Expert assessors**

**Lynn V. Dicks**, University of Cambridge, UK **Ian Hodge**, University of Cambridge, UK **Clunie Keenleyside**, Institute for European Environmental Policy, UK **Will Peach**, Royal Society for the Protection of Birds, UK **Nicola Randall**, Harper Adams University, UK **Jörn Scharlemann**, United Nations Environment Programme *—* World Conservation Monitoring Centre, UK **Gavin Siriwardena**, British Trust for Ornithology, UK **Henrik Smith**, Lund University, Sweden **Rebecca K. Smith**, University of Cambridge, UK **William J. Sutherland**, University of Cambridge, UK

**Scope of assessment**: for native farmland wildlife in northern and western Europe (European countries west of Russia, but not south of France, Switzerland, Austria, Hungary and Romania).

**Assessed:** 2014.

**Effectiveness measure** is the % of experts that answered yes to the question: based on the evidence presented does this intervention benefit wildlife? (Yes, no or don't know).

**Certainty measure** is the median % score for the question: how much do we understand the extent to which this intervention benefits wildlife on farmland? (0 = no evidence, 100% = certainty).

**Harm measure** was not scored for this synopsis.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 4.1 All farming systems



## **Beneficial**

## **Create uncultivated margins around intensive arable or pasture fields**

Twenty studies (including one randomized, replicated, controlled trial) from seven countries found uncultivated margins support more invertebrates, small mammal species or higher plant diversity than other habitats. Four studies (including two replicated studies from the UK) found positive associations between birds and uncultivated margins. Fifteen studies (including one randomized, replicated, controlled trial) from four countries found naturally regenerated margins had lower invertebrate or plant abundance or diversity than conventional fields or sown margins. Six studies (one randomized, replicated, controlled) from three countries found uncultivated margins did not have higher plant or invertebrate abundance or diversity than cropped or sown margins. *Assessment: beneficial (effectiveness 100%; certainty 63%).*

http://www.conservationevidence.com/actions/63

## **Plant grass buffer strips/margins around arable or pasture fields**

Twenty studies (including two randomized, replicated, controlled studies) from four countries found grass margins benefited invertebrates, including increases in abundance or diversity. Nine studies (including two replicated, controlled trials) from the UK found grass buffer strips benefit birds, with increased numbers, diversity or use. Seven replicated studies (four controlled, two randomized) from two countries found grass buffer strips increased plant cover and species richness, a review found benefits to plants. Five studies (two replicated, controlled) from two countries found benefits to small mammals. Six (including three replicated, controlled trials) from two countries found no clear effect on invertebrate or bird numbers. *Assessment: beneficial (effectiveness 90%; certainty 65%).*

http://www.conservationevidence.com/actions/246

#### **Plant nectar flower mixture/wildflower strips**

Forty-one studies (including one randomized, replicated, controlled trial) from eight countries found flower strips increased invertebrate numbers or diversity. Ten studies (two replicated, controlled) found invertebrates visited flower strips. Fifteen studies (two randomized, replicated, controlled) found mixed or negative effects on invertebrates. Seventeen studies (one randomized, replicated, controlled) from seven countries found more plants or plant species on flower strips, four did not. Five studies (two randomized, replicated, controlled) from two countries found bird numbers, diversity or use increased in flower strips, two studies did not. Five studies (four replicated) found increases in small mammal abundance or diversity in flower strips. *Assessment: beneficial (effectiveness 100%; certainty 75%).*

http://www.conservationevidence.com/actions/442

#### **Plant wild bird seed or cover mixture**

Fifteen studies (including a systematic review) from the UK found fields sown with wild bird cover mix had more birds or bird species than other farmland habitats. Six studies (including two replicated trials) from the UK found birds used wild bird cover more than other habitats. Nine replicated studies from France and the UK found mixed or negative effects on birds. Eight studies (including two randomized, replicated, controlled studies) from the UK found wild bird cover had more invertebrates, four (including two replicated trials) found mixed or negative effects on invertebrate numbers. Six studies (including two replicated, controlled trials) from the UK found wild bird cover mix benefited plants, two replicated studies did not. *Assessment: beneficial (effectiveness 100%; certainty 65%).*

http://www.conservationevidence.com/actions/594

## **Provide or retain set-aside areas in farmland**

Thirty-seven studies (one systematic review, no randomized, replicated, controlled trials) compared use of set-aside areas with control farmed fields. Twenty-one (including the systematic review) showed benefits to, or higher use by, all wildlife groups considered. Thirteen studies found some species or groups used set-aside more than crops; others did not. Two found higher Eurasian skylark reproductive success and one study found lower success on set-aside than control fields. Four studies found set-aside had no effect on wildlife, one found an adverse effect. Two studies found neither insects nor small mammals preferred set-aside. *Assessment: beneficial (effectiveness 90%; certainty 70%).*

http://www.conservationevidence.com/actions/156

#### **Likely to be beneficial**

#### **Manage ditches to benefit wildlife**

Five studies (including one replicated, controlled study) from the UK and the Netherlands found ditch management had positive effects on numbers, diversity or biomass of some or all invertebrates, amphibians, birds or plants studied. Three studies from the Netherlands and the UK (including two replicated site comparisons) found negative or no clear effects on plants or some birds. *Assessment: likely to be beneficial (effectiveness 40%; certainty 45%).*

#### **Manage hedgerows to benefit wildlife (includes no spray, gap-filling and laying)**

Ten studies from the UK and Switzerland (including one randomized, replicated, controlled trial) found managing hedges for wildlife increased berry yields, diversity or abundance of plants, invertebrates or birds. Five UK studies (including one randomized, replicated, controlled trial) found plants, bees and farmland birds were unaffected by hedge management. Two replicated studies found hedge management had mixed effects on invertebrates or reduced hawthorn berry yield. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%).*

http://www.conservationevidence.com/actions/116

### **Pay farmers to cover the cost of conservation measures (as in agri-environment schemes)**

For birds, twenty-four studies (including one systematic review) found increases or more favourable trends in bird populations, while eleven studies (including one systematic review) found negative or no effects of agri-environment schemes. For plants, three studies found more plant species, two found fewer plant species and seven found little or no effect of agri-environment schemes. For invertebrates, five studies found increases in abundance or species richness, while six studies found little or no effect of agri-environment schemes. For mammals, one replicated study found positive effects of agri-environment schemes and three studies found mixed effects in different regions or for different species. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%).*

http://www.conservationevidence.com/actions/700

#### **Provide supplementary food for birds or mammals**

Nine studies (two randomized, replicated, controlled) from France, Sweden and the UK found providing supplementary food increased abundance, overwinter survival or productivity of some birds. Two of the studies did not separate the effects of several interventions. Four studies (one replicated, controlled and one randomized, replicated) from Finland and the UK found some birds or mammals used supplementary food. Six replicated studies (three controlled) from Sweden and the UK found no clear effect on some birds or plants. *Assessment: likely to be beneficial (effectiveness 90%; certainty 50%).*

## **Unknown effectiveness (limited evidence)**

#### **Connect areas of natural or semi-natural habitat**

All four studies (including two replicated trials) from the Czech Republic, Germany and the Netherlands investigating the effects of linking patches of natural or semi-natural habitat found some colonization by invertebrates or mammals. Colonization by invertebrates was slow or its extent varied between taxa. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 15%).*

http://www.conservationevidence.com/actions/579

### **Increase the proportion of semi-natural habitat in the farmed landscape**

Of five studies monitoring the effects of the Swiss Ecological Compensation Areas scheme at a landscape scale (including three replicated site comparisons), one found an increase in numbers of birds of some species, two found no effect on birds and three found some species or groups increasing and others decreasing. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 20%).*

http://www.conservationevidence.com/actions/145

#### **Make direct payments per clutch for farmland birds**

Two replicated, controlled studies from the Netherlands found per clutch payments did not increase overall bird numbers. A replicated site comparison from the Netherlands found more birds bred on 12.5 ha plots under management including per-clutch payments but there were no differences at the field-scale. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 20%).*

http://www.conservationevidence.com/actions/146

## **Manage the agricultural landscape to enhance floral resources**

A large replicated, controlled study from the UK found the number of long-tongued bumblebees on field margins was positively correlated with the number of 'pollen and nectar' agri-environment agreements in a 10 km square. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%).*

http://www.conservationevidence.com/actions/362

#### **Mark bird nests during harvest or mowing**

A replicated study from the Netherlands found that marked northern lapwing nests were less likely to fail as a result of farming operations than unmarked nests. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 15%).*

http://www.conservationevidence.com/actions/148

#### **Plant new hedges**

Two studies (including one replicated trial) from France and the UK found new hedges had more invertebrates or plant species than fields or field margins. A review found new hedges had more ground beetles than older hedges. However, an unreplicated site comparison from Germany found only two out of 85 ground beetle species dispersed along new hedges. A review found lower pest outbreaks in areas with new hedges. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 25%).*

http://www.conservationevidence.com/actions/538

#### **Provide nest boxes for bees (solitary bees or bumblebees)**

Ten studies (nine replicated) from Germany, Poland and the UK found solitary bee nest boxes were used by bees. Two replicated trials from the UK found bumblebee nest boxes had very low uptake. Two replicated studies found the local population size or number of emerging red mason bees increased when nest boxes were provided. A replicated trial in Germany found the number of occupied solitary bee nests almost doubled over three years with repeated nest box provision. *Assessment: unknown effectiveness — limited evidence (effectiveness 90%; certainty 38%).*

http://www.conservationevidence.com/actions/80

#### **Provide nest boxes for birds**

Two studies (including one before-and-after trial) from the Netherlands and the UK found providing nest boxes increased the number of clutches or breeding adults of two bird species. A replicated study from Switzerland found nest boxes had mixed effects on the number of broods produced by two species. Eight studies (six replicated) from five countries found nest boxes were used by birds. A controlled study from the UK found one species did not use artificial nest sites. Three replicated studies (one paired) from the UK and Sweden found box location influenced use or nesting success. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 23%).*

http://www.conservationevidence.com/actions/155

## **Provide other resources for birds (water, sand for bathing)**

A small study in France found grey partridge density was higher in areas where water, shelter, sand and food were provided. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 1%).*

http://www.conservationevidence.com/actions/117

#### **Provide refuges during harvest or mowing**

A replicated study from France found mowing refuges reduced contact between mowing machinery and unfledged quails and corncrakes. A replicated controlled study and a review from the UK found Eurasian skylark did not use nesting refuges more than other areas. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 11%).*

http://www.conservationevidence.com/actions/147

#### **No evidence found (no assessment)**


# 4.2 Arable farming


#### **Beneficial**

## **Create skylark plots**

All four studies (two replicated, controlled trials) from Switzerland and the UK investigating the effect of skylark plots on Eurasian skylarks found positive effects, including increases in population size. A replicated study from Denmark found skylarks used undrilled patches in cereal fields. Three studies (one replicated, controlled) from the UK found benefits to plants and invertebrates. Two replicated studies (one controlled) from the UK found no significant differences in numbers of invertebrates or seedeating songbirds. *Assessment: beneficial (effectiveness 100%; certainty 80%).*

http://www.conservationevidence.com/actions/540

### **Leave cultivated, uncropped margins or plots (includes 'lapwing plots')**

Seventeen of nineteen individual studies looking at uncropped, cultivated margins or plots (including one replicated, randomized, controlled trial) primarily from the UK found benefits to some or all target farmland bird species, plants, invertebrates or mammals. Two studies (one replicated) from the UK found no effect on ground beetles or most farmland birds. Two replicated site comparisons from the UK found cultivated, uncropped margins were associated with lower numbers of some bird species or age groups in some areas. *Assessment: beneficial (effectiveness 100%; certainty 65%).*

http://www.conservationevidence.com/actions/562

#### **Likely to be beneficial**

#### **Create beetle banks**

Five reports from two replicated studies (one controlled) and a review from Denmark and the UK found beetle banks had positive effects on invertebrate numbers, diversity or distributions. Five replicated studies (two controlled) found lower or no difference in invertebrate numbers. Three studies (including a replicated, controlled trial) from the UK found beetle banks, alongside other management, had positive effects on bird numbers or usage. Three studies (one replicated site comparison) from the UK found mixed or no effects on birds, two found negative on no clear effects on plants. Two studies (one controlled) from the UK found harvest mice nested on beetle banks. *Assessment: likely to be beneficial (effectiveness 80%; certainty 60%).*

http://www.conservationevidence.com/actions/651

## **Leave overwinter stubbles**

Eighteen studies investigated the effects of overwinter stubbles. Thirteen studies (including two replicated site comparisons and a systematic review) from Finland, Switzerland and the UK found leaving overwinter stubbles benefits some plants, invertebrates, mammals or birds. Three UK studies (one randomized, replicated, controlled) found only certain birds were positively associated with overwinter stubbles. *Assessment: likely to be beneficial (effectiveness 90%; certainty 50%).*

http://www.conservationevidence.com/actions/695

## **Reduce tillage**

Thirty-four studies (including seven randomized, replicated, controlled trials) from nine countries found reducing tillage had some positive effects on invertebrates, weeds or birds. Twenty-seven studies (including three randomized, replicated, controlled trials) from nine countries found reducing tillage had negative or no clear effects on some invertebrates, plants, mammals or birds. Three of the studies did not distinguish between the effects of reducing tillage and reducing chemical inputs. *Assessment: likely to be beneficial (effectiveness 60%; certainty 60%).*

http://www.conservationevidence.com/actions/126

### **Undersow spring cereals, with clover for example**

Eleven studies (including three randomized, replicated, controlled trials) from Denmark, Finland, Switzerland and the UK found undersowing spring cereals benefited some birds, plants or invertebrates, including increases in numbers or species richness. Five studies (including one replicated, randomized, controlled trial) from Austria, Finland and the UK found no benefits to invertebrates, plants or some birds. *Assessment: likely to be beneficial (effectiveness 60%; certainty 43%).*

#### **Unknown effectiveness (limited evidence)**

#### **Convert or revert arable land to permanent grassland**

All seven individual studies (including two replicated, controlled trials) from the Czech Republic, Denmark and the UK looking at the effects of reverting arable land to grassland found no clear benefits to birds, mammals or plants. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 20%).*

http://www.conservationevidence.com/actions/561

#### **Create rotational grass or clover leys**

A controlled study from Finland found more spiders and fewer pest insects in clover leys than the crop. A replicated study from the UK found grass leys had fewer plant species than other conservation habitats. A UK study found newer leys had lower earthworm abundance and species richness than older leys. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 10%).*

http://www.conservationevidence.com/actions/643

#### **Increase crop diversity**

Four studies (including one replicated, controlled trial) from Belgium, Germany and Hungary found more ground beetle or plant species or individuals in fields with crop rotations or on farms with more crops in rotation than monoculture fields. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 9%).*

http://www.conservationevidence.com/actions/560

#### **Plant cereals in wide-spaced rows**

Two studies (one randomized, replicated, controlled) from the UK found planting cereals in wide-spaced rows had inconsistent, negative or no effects on plant and invertebrate abundance or species richness. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 18%).*

### **Plant crops in spring rather than autumn**

Seven studies (including two replicated, controlled trials) from Denmark, Sweden and the UK found sowing crops in spring had positive effects on farmland bird numbers or nesting rates, invertebrate numbers or weed diversity or density. Three of the studies found the effects were seasonal. A review of European studies found fewer invertebrates in spring wheat than winter wheat. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 35%).*

http://www.conservationevidence.com/actions/137

## **Plant nettle strips**

A small study from Belgium found nettle strips in field margins had more predatory invertebrate species than the crop, but fewer individuals than the crop or natural nettle stands. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%).*

http://www.conservationevidence.com/actions/118

#### **Sow rare or declining arable weeds**

Two randomized, replicated, controlled studies from the UK identified factors important in establishing rare or declining arable weeds, including type of cover crop, cultivation and herbicide treatment. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 15%).*

http://www.conservationevidence.com/actions/642

#### **No evidence found (no assessment)**


#### **Evidence not assessed**

## **Implement 'mosaic management', a Dutch agri-environment option**

A replicated, controlled before-and-after study from the Netherlands found mosaic management had mixed effects on population trends of wading bird species. A replicated, paired sites study from the Netherlands found one bird species had higher productivity under mosaic management. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/130

#### **Plant more than one crop per field (intercropping)**

All five studies (including three randomized, replicated, controlled trials) from the Netherlands, Poland, Switzerland and the UK looking at the effects of planting more than one crop per field found increases in the number of earthworms or ground beetles. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/124

#### **Take field corners out of management**

A replicated site comparison from the UK found a positive correlation between grey partridge overwinter survival and taking field corners out of management. Brood size, ratio of young to old birds and density changes were unaffected. *Assessment: this intervention has not been assessed.*


### **Unknown effectiveness (limited evidence)**

## **Maintain traditional orchards**

A replicated, controlled site comparison from Germany found more plant species in mown orchards than grazed or abandoned ones, but found no effects on wasps or bees. Two replicated site comparisons from Germany and Switzerland found traditional orchards managed under agri-environment schemes either did not have more plant species than controls or offered no clear benefits to birds. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 15%).*

http://www.conservationevidence.com/actions/703

#### **No evidence found (no assessment)**


# 4.4 Livestock farming



## **Beneficial**

## **Restore or create species-rich, semi-natural grassland**

Twenty studies (including three randomized, replicated, controlled trials) from six countries found restored species-rich, semi-natural grasslands had similar invertebrate, plant or bird diversity or abundance to other grasslands. Seven studies (two randomized, replicated, controlled trials) from five countries found no clear effect on plant or invertebrate numbers, three replicated studies (of which two site comparisons) from two countries found negative effects. Forty studies (including six randomized, replicated, controlled trials) from nine countries identified effective techniques for restoring species-rich grassland. *Assessment: beneficial (effectiveness 100%; certainty 73%).*

http://www.conservationevidence.com/actions/133

## **Use mowing techniques to reduce mortality**

Seven studies (including two replicated trials, one controlled and one randomized) from Germany, Ireland, Switzerland and the UK found mowing techniques that reduced mortality or injury in amphibians, birds, invertebrates or mammals. A review found the UK corncrake population increased around the same time that Corncrake Friendly Mowing was introduced and a replicated trial found mowing from the field centre outwards reduced corncrake chick mortality. *Assessment: beneficial (effectiveness 100%; certainty 78%).*

## **Likely to be beneficial**

## **Delay mowing or first grazing date on grasslands**

Eight studies (including a European systematic review) from the Netherlands, Sweden and the UK found delaying mowing or grazing benefited some or all plants, invertebrates or birds, including increases in numbers or productivity. Three reviews found the UK corncrake population increased following management that included delayed mowing. Six studies (including a European systematic review) from five countries found no clear effect on some plants, invertebrates or birds. *Assessment: likely to be beneficial (effectiveness 60%; certainty 45%).*

http://www.conservationevidence.com/actions/131

#### **Leave uncut strips of rye grass on silage fields**

Four studies (including two replicated, controlled trials) from the UK found uncut strips of rye grass benefited some birds, with increased numbers. A randomized, replicated, controlled study from the UK found higher ground beetle diversity on uncut silage plots, but only in the third study year. *Assessment: likely to be beneficial (effectiveness 80%; certainty 49%).*

http://www.conservationevidence.com/actions/132

#### **Maintain species-rich, semi-natural grassland**

Nine studies (including two randomized, replicated before-and-after trials) from Switzerland and the UK looked at the effectiveness of agri-environment schemes in maintaining species-rich grassland and all except one found mixed results. All twelve studies (including a systematic review) from six countries looking at grassland management options found techniques that improved or maintained vegetation quality. A site comparison from Finland and Russia found butterfly communities were more affected by grassland age and origin than present management. *Assessment: likely to be beneficial (effectiveness 80%; certainty 60%).*

## **Maintain traditional water meadows (includes management for breeding and/or wintering waders/waterfowl)**

Four studies (including a replicated site comparison) from Belgium, Germany, the Netherlands and the UK found maintaining traditional water meadows increased numbers of some birds or plant diversity. One bird species declined. Two studies (including a replicated site comparison from the Netherlands) found mixed or inconclusive effects on birds, plants or wildlife generally. A replicated study from the UK found productivity of one wading bird was too low to sustain populations in some areas of wet grassland managed for wildlife. *Assessment: likely to be beneficial (effectiveness 56%; certainty 50%).*

http://www.conservationevidence.com/actions/696

## **Maintain upland heath/moorland**

Eight studies (including one randomized, replicated, controlled trial) from the UK found management, including reducing grazing, can help to maintain the conservation value of upland heath or moorland. Benefits included increased numbers of plants or invertebrates. Three studies (including a before-and-after trial) from the UK found management to maintain upland heath or moorland had mixed effects on some wildlife groups. Four studies (including a controlled site comparison) from the UK found reducing grazing had negative impacts on soil organisms, but a randomized, replicated before-and-after study found heather cover declined where grazing intensity had increased. *Assessment: likely to be beneficial (effectiveness 90%; certainty 50%).*

http://www.conservationevidence.com/actions/647

## **Reduce management intensity on permanent grasslands (several interventions at once)**

Eleven studies (including four replicated site comparisons) from three countries found reducing management intensity benefited plants. Sixteen studies (including four paired site comparisons) from four countries found benefits to some or all invertebrates. Five studies (including one paired, replicated site comparison) from four countries found positive effects on some or all birds. Twenty-one studies (including two randomized, replicated, controlled trials) from six countries found no clear effects of reducing management intensity on some or all plants, invertebrates or birds. Five studies (including two paired site comparisons) from four countries found negative effects on plants, invertebrates or birds. *Assessment: likely to be beneficial (effectiveness 100%; certainty 60%).*

http://www.conservationevidence.com/actions/69

#### **Restore or create traditional water meadows**

Three studies (two before-and-after trials) from Sweden and the UK looked at bird numbers following water meadow restoration, one found increases, one found increases and decreases, one found no increases. Seventeen studies (two randomized, replicated, controlled) from six countries found successful techniques for restoring wet meadow plant communities. Three studies (one replicated, controlled) from four countries found restoration of wet meadow plant communities had reduced or limited success. *Assessment: likely to be beneficial (effectiveness 100%; certainty 50%).*

http://www.conservationevidence.com/actions/119

#### **Unknown effectiveness (limited evidence)**

#### **Add yellow rattle seed** *Rhinanthus minor* **to hay meadows**

A review from the UK reported that hay meadows had more plant species when yellow rattle was present. A randomized, replicated controlled trial in the UK found yellow rattle could be established by 'slot seeding'. *Assessment: unknown effectiveness — limited evidence (effectiveness 70%; certainty 20%).*

http://www.conservationevidence.com/actions/129

#### **Employ areas of semi-natural habitat for rough grazing (includes salt marsh, lowland heath, bog, fen)**

Three studies (two replicated) from the UK and unspecified European countries found grazing had positive effects on birds, butterflies or biodiversity generally. A series of site comparisons from the UK found one bird species used heathland managed for grazing as feeding but not nesting sites. Two studies (one replicated site comparison) from the UK found grazing had negative effects on two bird species. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%).*

## **Exclude livestock from semi-natural habitat (including woodland)**

Three studies (including one randomized, replicated, controlled trial) from Ireland and the UK found excluding livestock from semi-natural habitats benefited plants and invertebrates. Three studies (one replicated, controlled and one replicated paired sites comparison) from Ireland and the UK did not find benefits to plants or birds. Two studies (one replicated, controlled and a review) from Poland and the UK found limited or mixed effects. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 15%).*

http://www.conservationevidence.com/actions/150

### **Maintain wood pasture and parkland**

A randomized, replicated, controlled trial in Sweden found annual mowing on wood pasture maintained the highest number of plant species. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%).*

http://www.conservationevidence.com/actions/649

#### **Plant cereals for whole crop silage**

A replicated study from the UK found cereal-based whole crop silage had higher numbers of some birds than other crops. A review from the UK reported that seed-eating birds avoided cereal-based whole crop silage in winter, but used it as much as spring barley in summer. *Assessment: unknown effectiveness — limited evidence (effectiveness 80%; certainty 28%).*

http://www.conservationevidence.com/actions/149

### **Raise mowing height on grasslands**

Three studies (including one replicated, controlled trial) from the UK or unspecified European countries found raised mowing heights caused less damage to amphibians and invertebrates or increased Eurasian skylark productivity. Two studies (one randomized, replicated, controlled) from the UK found no effect on bird or invertebrate numbers and a replicated study from the UK found young birds had greater foraging success in shorter grass. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 35%).*

#### **Restore or create upland heath/moorland**

A small trial in northern England found moorland restoration increased the number of breeding northern lapwing. A UK review concluded that vegetation changes were slow during the restoration of heather moorland from upland grassland. *Assessment: unknown effectiveness — limited evidence (effectiveness 78%; certainty 20%).*

http://www.conservationevidence.com/actions/650

#### **Restore or create wood pasture**

A replicated, controlled trial in Belgium found survival and growth of tree seedlings planted in pasture was enhanced when they were protected from grazing. A replicated study in Switzerland found cattle browsing had negative effects on tree saplings. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 5%).*

http://www.conservationevidence.com/actions/644

### **Use traditional breeds of livestock**

Three studies (one replicated) from the UK found the breed of livestock affected vegetation structure, invertebrate communities and the amount of plants grazed. A replicated trial from France, Germany and the UK found no difference in the number of plant species or the abundance of birds, invertebrates or mammals between areas grazed by traditional or commercial livestock. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 20%).*

http://www.conservationevidence.com/actions/539

#### **Likely to be ineffective or harmful**

### **Reduce grazing intensity on grassland (including seasonal removal of livestock)**

Fifteen studies (including three randomized, replicated, controlled trials) from four countries found reducing grazing intensity benefited birds, invertebrates or plants. Three studies (including one randomized, replicated, controlled trial) from the Netherlands and the UK found no benefit to plants or invertebrates. Nine studies (including a systematic review) from France, Germany and the UK found mixed effects for some or all wildlife groups. The systematic review concluded that intermediate grazing levels are usually optimal but different wildlife groups are likely to have different grazing requirements. *Assessment: likely to be ineffective (effectiveness 30%; certainty 70%).*

http://www.conservationevidence.com/actions/704

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


#### **Evidence not assessed**

#### **Create open patches or strips in permanent grassland**

A randomized, replicated, controlled study from the UK found more Eurasian skylarks used fields containing open strips, but numbers varied. A randomized, replicated, controlled study from the UK found insect numbers on grassy headlands initially dropped when strips were cleared. *Assessment:this intervention has not been assessed.*

http://www.conservationevidence.com/actions/563

## **Provide short grass for birds**

A replicated UK study found two bird species spent more time foraging on short grass than longer grass. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/115

## **Use mixed stocking**

A replicated, controlled study in the UK found more spiders, harvestmen and pseudoscorpions in grassland grazed by sheep-only than grassland grazed by sheep and cattle. Differences were only found when suction sampling not pitfall-trapping. *Assessment: this intervention has not been assessed.*

# 4.5 Threat: Residential and commercial development


## **Unknown effectiveness (limited evidence)**

### **Provide owl nest boxes (tawny owl, barn owl)**

Two studies (one before-and-after study) from the Netherlands and the UK found providing nest boxes increased barn owl populations. A replicated study from the UK found a decrease in the proportion of breeding barn owls was not associated with the number of nest boxes. *Assessment: unknown effectiveness — limited evidence (effectiveness 100%; certainty 33%).*

http://www.conservationevidence.com/actions/154

#### **No evidence found (no assessment)**


# 4.6 Threat: Agri-chemicals


## **Beneficial**

## **Leave headlands in fields unsprayed (conservation headlands)**

Twenty-two studies from 14 experiments (including two randomized, replicated, controlled) from five countries found conservation headlands had higher invertebrate or plant diversity than other habitats, twelve studies from ten experiments (three randomized, replicated, controlled) did not. Twenty-seven studies from 15 experiments (of which 13 replicated, controlled) from five countries found positive effects on abundance or behaviour of some wildlife groups. Nineteen studies from 13 experiments

(12 replicated, controlled) from four countries found similar, or lower, numbers of birds, invertebrates or plants on conservation headlands than other habitats. *Assessment: beneficial (effectiveness 90%; certainty 75%).*

http://www.conservationevidence.com/actions/652

## **Reduce fertilizer, pesticide or herbicide use generally**

Thirty-four studies (including a systematic review) from 10 countries found reducing fertilizer, pesticide or herbicide inputs benefited some invertebrates, plants or birds. Twenty-five studies (including seven randomized, replicated, controlled trials) from eight countries found negative or no clear effects on some invertebrates, plants or birds. *Assessment: beneficial (effectiveness 100%; certainty 70%).*

http://www.conservationevidence.com/actions/139

#### **Use organic rather than mineral fertilizers**

Fourteen studies (including four randomized, replicated, controlled trials) from six countries found areas treated with organic rather than mineral fertilizers had more plants or invertebrates or higher diversity. A randomized, replicated, controlled trial from the UK found no effect on weed numbers. Two studies (including a small trial from Belgium) found organic fertilizers benefited invertebrates, a UK review found that in large quantities they did not. *Assessment: beneficial (effectiveness 100%; certainty 70%).*

http://www.conservationevidence.com/actions/134

#### **Likely to be beneficial**

#### **Reduce chemical inputs in grassland management**

Six studies (including a randomized, replicated, controlled beforeand-after trial) from three countries found stopping fertilizer inputs on grassland improved plant or invertebrate species richness or abundance. Two reviews from the Netherlands and the UK found no or low fertilizer input grasslands favour some birds and invertebrates. Five studies (two replicated trials of which one randomized and one replicated) from three countries found no clear effects on invertebrates or plants. *Assessment: likely to be beneficial (effectiveness 90%; certainty 60%).*

## **Unknown effectiveness (limited evidence)**

## **Provide buffer strips alongside water courses (rivers and streams)**

Three studies (including one replicated site comparison) from the Netherlands and the UK found riparian buffer strips increased diversity or abundance of plants, invertebrates or birds and supported vegetation associated with water vole habitats. Two replicated site comparisons from France and Ireland found farms with buffer strips did not have more plant species than farms without strips. *Assessment: unknown effectiveness—limited evidence (effectiveness 10%; certainty 15%).*

http://www.conservationevidence.com/actions/120

#### **Restrict certain pesticides**

A small UK study found two fungicides that reduced insect abundance less than an alternative. A replicated, controlled trial in Switzerland found applying slug pellets in a band at the field edge was as effective as spreading the pellets across the field. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 5%).*

http://www.conservationevidence.com/actions/565

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Buffer in-field ponds

#### **Evidence not assessed**

#### **Make selective use of spring herbicides**

A randomized, replicated, controlled study from the UK found spring herbicides had some benefits for beneficial weeds and arthropods. *Assessment: this intervention has not been assessed.*

# 4.7 Threat: Transport and service corridors

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for transport and service corridors? No evidence found (no assessment)** ● Manage land under power lines to benefit wildlife

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Manage land under power lines to benefit wildlife

# 4.8 Threat: Hunting and trapping (for pest control, food or sport)


**Evidence not assessed** ● Use scaring devices (e.g. gas guns) and other deterrents to reduce persecution of native species

during shoots

### **Unknown effectiveness (limited evidence)**

#### **Enforce legislation to protect birds against persecution**

Two before-and-after studies from Denmark and the UK found increased numbers or survival of raptors under legislative protection. *Assessment: unknown effectiveness — limited evidence (effectiveness 90%; certainty 18%).*

## **Provide 'sacrificial' grasslands to reduce the impact of wild geese on crops**

All six studies from the UK (including four replicated, controlled trials) found that managing grasslands for geese increased the number of geese using these areas. Four of these studies found geese were moving within the study sites. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 5%).*

http://www.conservationevidence.com/actions/641

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


#### **Evidence not assessed**

## **Use scaring devices (e.g. gas guns) and other deterrents to reduce persecution of native species**

A replicated, controlled trial in Germany found phosphorescent tape was more effective than normal yellow tape at deterring one of three mammal species. *Assessment: this intervention has not been assessed.*

# 4.9 Threat: Natural system modification


## **Likely to be beneficial**

## **Raise water levels in ditches or grassland**

Eight studies (including two replicated, controlled trials) from Denmark, the Netherlands and the UK found raising water levels increased numbers of birds, invertebrates or plants or allowed wet grassland plant species to establish more rapidly. Three studies (two replicated) from the Netherlands and the UK found raising water levels had negative, limited or no effects on plants or birds. A replicated study from the UK found unflooded pastures had a greater weight of soil invertebrates than flooded pastures. *Assessment: likely to be beneficial (effectiveness 100%; certainty 55%).*

#### **Unknown effectiveness (limited evidence)**

#### **Create scrapes and pools**

Five studies (including a replicated, controlled, paired trial) from Sweden and the UK found creating scrapes and pools provided habitat for birds, invertebrates or plants or increased invertebrate diversity. Two replicated studies (one controlled, paired) from Ireland and the UK found mixed or no differences in invertebrate numbers between created ponds and controls or natural ponds. A study in Sweden found fewer fish species in constructed than natural wetlands. *Assessment: unknown effectiveness — limited evidence (effectiveness 100%; certainty 28%).*

http://www.conservationevidence.com/actions/153

#### **Manage heather by swiping to simulate burning**

A replicated, controlled trial from the UK found heather moorland subject to flailing had fewer plant species than burned plots but more species than unflailed plots. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 9%).*

http://www.conservationevidence.com/actions/151

#### **Manage heather, gorse or grass by burning**

A long-term replicated, controlled trial in Switzerland found burning of chalk grassland did not increase the number of plant species. A replicated, controlled trial in the UK found more plant species on burned than unburned heather moorland. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 5%).*

http://www.conservationevidence.com/actions/152

#### **Remove flood defence banks to allow inundation**

A controlled before-and-after study from the UK found a stretch of river that was allowed to flood had more bird species and territories than a channelized section. A study from Belgium found flooding and mowing increased plant species richness in meadow plots. *Assessment: unknown effectiveness — limited evidence (effectiveness 80%; certainty 10%).*

## **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Re-wet moorland

# 4.10 Threat: Invasive and other problematic species

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for invasive and other problematic species?**


### **Likely to be beneficial**

## **Control predatory mammals and birds (foxes, crows, stoats and weasels)**

Eight studies (including a systematic review) from France and the UK found predator control (sometimes alongside other interventions) increased the abundance, population size or productivity of some birds. A randomized, replicated, controlled study from the UK did not. *Assessment: likely to be beneficial (effectiveness 90%; certainty 60%).*

http://www.conservationevidence.com/actions/699

## **Unknown effectiveness (limited evidence)**

#### **Control scrub**

A replicated site comparison from the UK found the number of young grey partridge per adult was negatively associated with management that included scrub control. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 2%).*

http://www.conservationevidence.com/actions/127

## **Control weeds without damaging other plants in conservation areas**

Two studies (one randomized, replicated, controlled) from the UK found that after specific plants were controlled, new plants established or diversity increased. A replicated, controlled laboratory and grassland study found a specific herbicide had negative impacts on one beetle species. Eleven studies investigated different methods of controlling plants. *Assessment: unknown effectiveness — limited evidence (effectiveness 90%; certainty 28%).*

http://www.conservationevidence.com/actions/123

### **Protect individual nests of ground-nesting birds**

Two randomized, replicated, controlled studies from Sweden found nest exclosures increased measures of ground-nesting bird productivity, however both found bird numbers or adult predation rates were unaffected or negatively affected by exclosures. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 13%).*

http://www.conservationevidence.com/actions/108

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Control grey squirrels


#### **Evidence not assessed**

#### **Control bracken**

A systematic review found repeated herbicide applications reduced bracken abundance but cutting may be equally effective. A laboratory trial found the same herbicide could inhibit the growth of mosses under certain conditions. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/105

## **Control invasive non-native plants on farmland (such as Himalayan balsam, Japanese knotweed)**

Two randomized, replicated, controlled trials in the Czech Republic found removing all giant hogweed flower heads at peak flowering time reduced seed production. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/104

### **Control mink**

A systematic review found trapping may be an effective method of reducing American mink populations. A study in the UK found mink were successfully eradicated from a large area by systematic trapping. *Assessment: this intervention has not been assessed.*

http://www.conservationevidence.com/actions/107

### **Provide medicated grit for grouse**

A controlled study from the UK found higher red grouse productivity where medicated grit was provided. *Assessment: this intervention has not been assessed.*

# 4.11 Threat: Education and awareness


## **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Provide specialist advice, assistance preparing conservation plans

#### **Evidence not assessed**

## **Provide training for land managers, farmers and farm advisers**

A study from the UK found farmers who were trained in how to implement agri-environment schemes created better quality wildlife habitat over five years. *Assessment: this intervention has not been assessed.*

# 5. FOREST CONSERVATION

**Har'el Agra, Simon Schowanek, Yohay Carmel, Rebecca K. Smith & Gidi Ne'eman**

**Expert assessors**

**Rhett Harrison**, Consultative Group on International Agricultural Research, Zambia **Keith Kirby**, University of Oxford, UK **Gillian Petrokofsky**, Biodiversity Institute Oxford, UK **Rebecca K. Smith**, University of Cambridge, UK **William J. Sutherland**, University of Cambridge, UK **Tom Swinfield**, Royal Society for the Protection of Birds, UK

**Scope of assessment**: for the conservation of forest habitat (not specific species within forests), including tropical forests, temperate forests, woodland, scrubland, shrubland and dry forests.

**Assessed:** 2016.

**Effectiveness measure** is the median % score.

**Certainty measure** is the median % certainty of evidence, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects on the forest habitat of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target habitat for each intervention. The assessment may therefore refer to different habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target habitats or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 5.1 Threat: Residential and commercial development

## 5.1.1 Housing and urban areas

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for residential and commercial development in housing and urban areas?**


## **No evidence found (no assessment)**


## 5.1.2 Tourism and recreation areas


#### **No evidence found (no assessment)**


## 5.2.1 Livestock farming

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for livestock farming?**


### **Likely to be beneficial**

### **Use wire fences within grazing areas to exclude livestock from specific forest sections**

Three of four studies, including one replicated, randomized, controlled study in Kenya, Israel, Mexico and Panama found that excluding livestock using wire fences increased the size, density or number of regenerating trees. One study found no effect on tree size and decreased tree density. Four of eight studies, including two replicated, randomized, controlled studies across the world found that excluding livestock using increased biomass, species richness, density or cover of understory plants. Four studies found mixed or no effects on understory plants. *Assessment: likely to be beneficial (effectiveness 58%; certainty 63%; harms 18%).*

http://www.conservationevidence.com/actions/1205

#### **Trade-off between benefit and harms**

#### **Prevent livestock grazing in forests**

One site comparison study in Israel found that preventing cattle grazing increased the density of seedlings and saplings. Two of three studies, including one replicated, controlled study, in Brazil, Costa Rica and the UK found that preventing livestock grazing increased survival, species richness or diversity of understory plants. One study found mixed effects. *Assessment: trade-offs between benefits and harms (effectiveness 69%; certainty 45%; harms 20%).*

http://www.conservationevidence.com/actions/1206

#### **Unknown effectiveness (limited evidence)**

#### **Reduce the intensity of livestock grazing in forests**

Two studies, including one replicated, randomized, controlled study, in the UK and Greece found that reducing grazing intensity increased the number of tree saplings or understory total weight. *Assessment: unknown effectiveness (effectiveness 78%; certainty 34%; harms 0%).*

http://www.conservationevidence.com/actions/1207

### **Shorten livestock grazing period or control grazing season in forests**

One of two studies, including one replicated, controlled study, in Spain and Australia found that shortening the grazing period increased the abundance and size of regenerating trees. One found no effect native plant species richness. One replicated study in the UK found that numbers of tree seedlings were higher following summer compared to winter grazing. *Assessment: unknown effectiveness (effectiveness 58%; certainty 33%; harms 0%).*

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Provide financial incentives not to graze.

# 5.3 Threat: Transport and service corridors

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for transport and service corridors? No evidence found (no assessment)** ● Maintain/create habitat corridors

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Maintain/create habitat corridors.

# 5.4 Threat: Biological resource use

## 5.4.1 Thinning and wood harvesting


#### **Beneficial**

#### **Log/remove trees within forests: effects on understory plants**

Eight of 12 studies, including four replicated, randomized, controlled studies, in India, Australia, Bolivia, Canada and the USA found that logging increased the density and cover or species richness and diversity of understory plants. Two studies found mixed and three found no effect. *Assessment: beneficial (effectiveness 65%; certainty 65%; harms 10%).*

http://www.conservationevidence.com/actions/1273

#### **Likely to be beneficial**

#### **Thin trees within forests: effects on understory plants**

Twenty five of 38 studies, including 12 replicated, randomized, controlled studies, across the world found that thinning trees increased the density and cover or species richness and diversity of understory plants. Nine studies found mixed and two no effects, and one found a decrease the abundance of herbaceous species. *Assessment: Likely to be beneficial (effectiveness 58%; certainty 73%; harms 13%).*

http://www.conservationevidence.com/actions/1211

#### **Thin trees within forests: effects on young trees**

Six of 12 studies, including two replicated, randomized, controlled studies, in Japan and the USA found that thinning increased the density of young trees and a study in Peru found it increased the growth rate of young trees. One study found thinning decreased the density and five found mixed or no effect on young trees. One replicated, controlled study in the USA found no effect on the density of oak acorns. *Assessment: Likely to be beneficial (effectiveness 60%; certainty 65%; harms 15%).*

http://www.conservationevidence.com/actions/1210

#### **Use shelterwood harvest instead of clearcutting**

Three replicated, controlled studies in Sweden and the USA found that shelterwood harvesting increased density of trees or plant diversity, or decreased grass cover compared with clearcutting. *Assessment: Likely to be beneficial (effectiveness 75%; certainty 55%; harms 15%).*

http://www.conservationevidence.com/actions/1214

#### **Trade-off between benefit and harms**

#### **Thin trees within forests: effects on mature trees**

Eleven of 12 studies, including two replicated, randomized, controlled studies, in Brazil, Canada, and the USA found that thinning trees decreased the density and cover of mature trees and in one case tree species diversity. Five of six studies, including one replicated, controlled, before-and-after study, in Australia, Sweden and the USA found that thinning increased mature tree size, the other found mixed effects. One of three studies, including two replicated controlled studies, in the USA found that thinning reduced the number of trees killed by beetles. *Assessment: trade-offs between benefits and harms (effectiveness 47%; certainty 55%; harms 35%).*

http://www.conservationevidence.com/actions/1209

#### **Unknown effectiveness (limited evidence)**

#### **Log/remove trees within forests: effects on young trees**

One of two replicated controlled studies in Canada and Costa Rica found that logging increased the density of young trees, the other found mixed effects. *Assessment: unknown effectiveness (effectiveness 50%; certainty 18%; harms 10%).*

http://www.conservationevidence.com/actions/1272

#### **Use partial retention harvesting instead of clearcutting**

Three studies, including one replicated, randomized, controlled study, in Canada found that using partial retention harvesting instead of clearcutting decreased the density of young trees. *Assessment: unknown effectiveness (effectiveness 5%; certainty 35%; harms 45%).*

## **Use summer instead of winter harvesting**

One replicated study in the USA found no effect of logging season on plant species richness and diversity. *Assessment: unknown effectiveness (effectiveness 0%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/1216

### **Unlikely to be beneficial**

## **Remove woody debris after timber harvest**

Two studies, including one replicated, randomized, controlled study, in France and the USA found no effect of woody debris removal on cover or species diversity of trees. One of six studies, including two replicated, randomized, controlled studies, in Ethiopia, Spain, Canada and the USA found that woody debris removal increased young tree density. One found that it decreased young tree density and three found mixed or no effect on density or survival. One of six studies, including two replicated, randomized, controlled studies, in the USA and France found that woody debris removal increased understory vegetation cover. Five studies found mixed or no effects on understory vegetation cover or species richness and diversity. *Assessment: unlikely to be beneficial (effectiveness 23%; certainty 50%; harms 10%).*

http://www.conservationevidence.com/actions/1213

#### **Likely to be ineffective or harmful**

#### **Log/remove trees within forests: effect on mature trees**

Three of seven studies, including two replicated, controlled studies, across the world found that logging trees decreased the density and cover of mature trees. Two found it increased tree density and two found no effect. Four of nine studies, including one replicated, randomized, controlled study, across the world found that logging increased mature tree size or diversity. Four found it decreased tree size or species richness and diversity, and two found no effect on mature tree size or diversity. One replicated, controlled study in Canada found that logging increased mature tree mortality rate. *Assessment: likely to be ineffective or harmful (effectiveness 35%; certainty 50%; harms 30%).*

## **Log/remove trees within forests: effect on effects on nonvascular plants**

Two of three studies, including one replicated, paired sites study, in Australia, Norway and Sweden found that logging decreased epiphytic plant abundance and fern fertility. One found mixed effects depending on species. *Assessment: likely to be ineffective or harmful (effectiveness 18%; certainty 40%; harms 50%).*

http://www.conservationevidence.com/actions/1270

## **Thin trees within forests: effects on non-vascular plants**

Three of four studies, including one replicated, randomized, controlled study, in Canada, Finland and Sweden found that thinning decreased epiphytic plant abundance and species richness. Three found mixed effects depending on thinning method and species. *Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 48%; harms 50%).*

http://www.conservationevidence.com/actions/1212

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 5.4.2 Harvest forest products


## **Unknown effectiveness (limited evidence)**

## **Adopt certification**

One replicated, site comparison study in Ethiopia found that deforestation risk was lower in certified than uncertified forests. One controlled, beforeand-after trial in Gabon found that, when corrected for logging intensity, although tree damage did not differ, changes in above-ground biomass were smaller in certified than in uncertified forests. *Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 3%).*

http://www.conservationevidence.com/actions/1150

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Sustainable management of non-timber products

## 5.4.3 Firewood

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for firewood?**


#### **No evidence found (no assessment)**


# 5.5.1 Changing fire frequency


#### **Trade-off between benefit and harms**

## **Use prescribed fire: effect on understory plants**

Eight of 22 studies, including seven replicated, randomized, controlled studies, in Australia, Canada and the USA found that prescribed fire increased the cover, density or biomass of understory plants. Six found it decreased plant cover and eight found mixed or no effect on cover or density. Fourteen of 24 studies, including 10 replicated, randomized, controlled studies, in Australia, France, West Africa and the USA found that fire increased species richness and diversity of understory plants. One found it decreased species richness and nine found mixed or no effect on understory plants. *Assessment: trade-offs between benefits and harms (effectiveness 55%; certainty 70%; harms 25%).*

http://www.conservationevidence.com/actions/1221

#### **Use prescribed fire: effect on young trees**

Five of 15 studies, including four replicated, randomized, controlled studies, in France, Canada and the USA found that prescribed fire increased the density and biomass of young trees. Two found that fire decreased young tree density. Eight found mixed or no effect on density and two found mixed effects on species diversity of young trees. Two replicated, controlled studies in the USA found mixed effects of prescribed fire on young tree survival. *Assessment: trade-offs between benefits and harms (effectiveness 45%; certainty 55%; harms 23%).*

http://www.conservationevidence.com/actions/1220

#### **Likely to be ineffective or harmful**

#### **Use prescribed fire: effect on mature trees**

Four of nine studies, including two replicated, randomized, controlled studies, in the USA found that prescribed fire decreased mature tree cover, density or diversity. Two studies found it increased tree cover or size, and four found mixed or no effect. Seven studies, including one replicated, randomized, controlled study, in the USA found that fire increased mature tree mortality. *Assessment: likely to be ineffective or harmful (effectiveness 25%; certainty 50%; harms 50%).*

http://www.conservationevidence.com/actions/1217

#### **No evidence found (no assessment)**


## 5.5.2 Water management

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for water management?**


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


# 5.5.3 Changing disturbance regime



#### **Trade-off between benefit and harms**

#### **Use clearcutting to increase understory diversity**

Three of nine studies, including four replicated, randomized, controlled studies, in Australia, Japan, Brazil, Canada and the USA found that clearcutting decreased density, species richness or diversity of mature trees. One study found it increased trees species richness and six found mixed or no effect or mixed effect on density, size, species richness or diversity. One replicated, randomized, controlled study in Finland found that clearcutting decreased total forest biomass, particularly of evergreen shrubs. Three of six studies, including five replicated, randomized, controlled studies, in Brazil, Canada and Spain found that clearcutting increased the density and species richness of young trees. One found it decreased young tree density and two found mixed or no effect. Eight of 12 studies, including three replicated, randomized, controlled studies, across the world found that clearcutting increased the cover or species richness of understory plants. Two found it decreased density or species richness, and two found mixed or no effect. *Assessment: trade-offs between benefits and harms (effectiveness 63%; certainty 65%; harms 30%).*

http://www.conservationevidence.com/actions/1222

### **Use group-selection harvesting**

Four of eight studies, including one replicated, controlled study, in Australia, Canada, Costa Rica and the USA found that group-selection harvesting increased cover or diversity of understory plants, or the density of young trees. Two studies found it decreased understory species richness or and biomass. Three studies found no effect on understory species richness or diversity or tree density or growth-rate. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 58%; harms 30%).*

## **Use shelterwood harvesting**

Six of seven studies, including five replicated, controlled studies, in Australia, Iran, Nepal and the USA found that shelterwood harvesting increased abundance, species richness or diversity or understory plants, as well as the growth and survival rate of young trees. One study found shelterwood harvesting decreased plant species richness and abundance and one found no effect on abundance. One replicated, controlled study in Canada found no effect on oak acorn production. *Assessment: trade-offs between benefits and harms (effectiveness 78%; certainty 70%; harms 28%).*

http://www.conservationevidence.com/actions/1223

## **Unknown effectiveness (limited evidence)**

## **Thin trees by girdling (cutting rings around tree trunks)**

One before-and-after study in Canada found that thinning trees by girdling increased understory plant species richness, diversity and cover. *Assessment: unknown effectiveness — limited evidence (effectiveness 58%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/1226

## **Use herbicides to thin trees**

One replicated, controlled study in Canada found no effect of using herbicide to thin trees on total plant species richness. *Assessment: unknown effectiveness — limited evidence (effectiveness 5%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/1225

### **Unlikely to be beneficial**

## **Use thinning followed by prescribed fire**

Three of six studies, including one replicated, randomized, controlled study, in the USA found that thinning followed by prescribed fire increased cover or abundance of understory plants, and density of deciduous trees. One study found it decreased tree density and species richness. Three studies found mixed or no effect or mixed effect on tree growth rate or density

of young trees. One replicated, controlled study Australia found no effect of thinning then burning on the genetic diversity of black ash. *Assessment: unlikely to be beneficial (effectiveness 35%; certainty 40%; harms 15%).*

http://www.conservationevidence.com/actions/1227

#### **No evidence found (no assessment)**


# 5.6 Threat: Invasive and other problematic species

## 5.6.1 Invasive plants


### **Unknown effectiveness (limited evidence)**

### **Manually/mechanically remove invasive plants**

Two replicated, controlled studies in Hawaii and Ghana found that removing invasive grass or weed species increased understory plant biomass or tree seedling height. Two replicated, controlled studies in the USA and Hawaii found no effect of removing invasive shrubs or plants on understory plant diversity or growth rate of native species. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 33%; harms 15%).*

## **Use herbicides to remove invasive plant species**

One replicated, randomized, controlled study in the USA found no effect of controlling invasive plants using herbicide on native plant species richness. *Assessment: unknown effectiveness — limited evidence (effectiveness 5%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/1229

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 5.6.2 Native plants

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for native plants? No evidence found (no assessment)** ● Manually/mechanically remove native plants

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Manually/mechanically remove native plants

## 5.6.3 Herbivores



## **Likely to be beneficial**

### **Use wire fences to exclude large native herbivores**

Two replicated, controlled studies in the USA found that excluding large herbivores increased tree density. One of three studies, including two replicated, paired-sites, before-and-after studies, in Canada, Bhutan and Ireland found that excluding large herbivores increased the biomass of young trees. One found it decreased the density of young trees and one found mixed effects on species. Five of 10 studies, including two replicated, randomized, controlled studies, across the world found that excluding large herbivores increased the cover or and size of understory plants. Six found no effect on the cover, seed density, species richness or diversity of understory plants. *Assessment: Likely to be beneficial (effectiveness 50%; certainty 65%; harms 10%).*

http://www.conservationevidence.com/actions/1230

#### **Unknown effectiveness (limited evidence)**

### **Use electric fencing to exclude large native herbivores**

One controlled study in South Africa found that using electric fencing to exclude elephants and nyalas increased tree density. *Assessment: Unknown effectiveness (effectiveness 65%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/1231

#### **No evidence found (no assessment)**


## 5.6.4 Rodents

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for rodents? Unknown effectiveness (limited evidence)** ● Control rodents

## **Unknown effectiveness (limited evidence)**

## **Control rodents**

One controlled study in New Zealand found that rodent control decreased native plant species richness and had no effect on total plant species richness. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%; harms 50%).*

http://www.conservationevidence.com/actions/1232

## 5.6.5 Birds


### **Unknown effectiveness (limited evidence)**

#### **Control birds**

One controlled study in Australia found that removing birds did not improve the health of the trees in a narrow-leaved peppermint forest. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 15%; harms 0%).*

# 5.7 Threat: Pollution


#### **Unknown effectiveness (limited evidence)**

#### **Maintain/create buffer zones**

One site comparison study in Australia found that a forest edge protected by a planted buffer strip had higher canopy cover and lower stem density, but similar understory species richness to an unbuffered forest edge. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

http://www.conservationevidence.com/actions/1168

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Remove nitrogen and phosphorus using harvested products.

# 5.8 Threat: Climate change and severe weather

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for climate change and severe weather? No evidence found (no assessment)** ● Prevent damage from strong winds

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Prevent damage from strong winds.

# 5.9 Habitat protection


#### **Unknown effectiveness (limited evidence)**

#### **Adopt community-based management to protect forests**

Two studies, including one replicated, before-and-after, site comparison, in Ethiopia and Nepal found that forest cover increased more in communitymanaged forests than in forests not managed by local communities. However, one replicated, site comparison study in Colombia found that deforestation rates in community-managed forests did not differ from deforestation rates in unmanaged forests. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 35%; harms 0%).*

http://www.conservationevidence.com/actions/1152

### **Legal protection of forests**

Two site comparison studies in Nigeria and Iran found that legal protection of forest increased tree species richness and diversity or the density of young trees. One replicated, paired site study in Mexico found no effect of forest protection on seed density and diversity of trees and shrubs. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1233

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Adopt Protected Species legislation (impact on forest management).

# 5.10 Habitat restoration and creation

## 5.10.1 Restoration after wildfire


## **Trade-off between benefit and harms**

### **Thin trees after wildfire**

Four of five replicated, controlled studies in Spain, Israel, Cananda and the USA found that thinning trees in burnt forest areas increased plant species richness, cover or survival of saplings. One study found thinning decreased plant biomass. One paired-site study in Canada found that logging after wildfire decreased species richness and diversity of mosses. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 50%; harms 38%).*

## **Unknown effectiveness (limited evidence)**

## **Remove burned trees**

Two replicated, controlled studies in Israel and Spain found that removing burned trees increased total plant species richness or the cover and species richness of some plant species. *Assessment: unknown effectiveness (effectiveness 60%; certainty 20%; harms 25%).*

http://www.conservationevidence.com/actions/1237

## **Likely to be ineffective or harmful**

#### **Sow tree seeds after wildfire**

Three studies, including one replicated, randomized, controlled study, in the USA found that sowing herbaceous plant seeds in burnt forest areas decreased the density of tree seedlings or the number and cover of native species. All three found no effect of seeding on total plant cover or species richness. *Assessment: likely to be ineffective or harmful (effectiveness 0%; certainty 43%; harms 40%).*

http://www.conservationevidence.com/actions/1236

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Plant trees after wildfire

## 5.10.2 Restoration after agriculture


## **Unknown effectiveness (limited evidence)**

## **Restore wood pasture (e.g. introduce grazing)**

One replicated paired study in Sweden found that partial harvesting in abandoned wood pastures increased tree seedling density, survival and growth. *Assessment: unknown effectiveness (effectiveness 65%; certainty 25%; harms 0%).*

http://www.conservationevidence.com/actions/1164

## 5.10.3 Manipulate habitat to increase planted tree survival during restoration

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for manipulating habitat to increase planted tree survival during restoration?**


#### **Unknown effectiveness (limited evidence)**

### **Apply herbicides after restoration planting**

One replicated, randomized, controlled study in the USA found that controlling vegetation using herbicides after restoration planting decreased plant species richness and diversity. *Assessment: unknown effectiveness (effectiveness 45%; certainty 25%; harms 40%).*

## **Cover the ground using techniques other than plastic mats after restoration planting**

One replicated, randomized, controlled study in the USA found that covering the ground with mulch after planting increased total plant cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 15%; harms 10%).*

http://www.conservationevidence.com/actions/1240

## **Cover the ground with plastic mats after restoration planting**

One replicated study in Canada found that covering the ground with plastic mats after restoration planting decreased the cover of herbecous plants and grasses. *Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1239

### **Use selective thinning after restoration planting**

One replicated, paired sites study in Canada found that selective thinning after restoration planting conifers increased the abundance of herbaceous species. *Assessment: unknown effectiveness (effectiveness 43%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/1238

## 5.10.4 Restore forest community


## **Unknown effectiveness (limited evidence)**

## **Build bird-perches to enhance natural seed dispersal**

One replicated, randomized, controlled, before-and-after study in Brazil found that sowing tree seeds increased the density and species richness of new trees. *Assessment: unknown effectiveness (effectiveness 50%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/1245

## **Plant a mixture of tree species to enhance diversity**

One replicated, randomized, controlled study in Brazil found that planting various tree species increased species richness, but had no effect on the density of new trees. One replicated, controlled study in Greece found that planting native tree species increased total plant species richness, diversity and cover. *Assessment: unknown effectiveness (effectiveness 50%; certainty 28%; harms 0%).*

http://www.conservationevidence.com/actions/1243

#### **Sow tree seeds**

One replicated, randomized, controlled, before-and-after study in Brazil found that sowing tree seeds increased the density and species richness of new trees. *Assessment: unknown effectiveness (effectiveness 60%; certainty 13%; harms 0%).*

http://www.conservationevidence.com/actions/1244

### **Water plants to preserve dry tropical forest species**

One replicated, controlled study in Hawaii found that watering plants increased the abundance and biomass of forest plants. *Assessment: unknown effectiveness (effectiveness 65%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/1242

#### **No evidence found (no assessment)**


# 5.10.5 Prevent/encourage leaf litter accumulation



## **Unknown effectiveness (limited evidence)**

#### **Remove or disturb leaf litter to enhance germination**

One of two replicated, controlled studies in Poland and Costa Rica found that removing leaf litter increased understory plant species richness. The two studies found that removal decreased understory plant cover or the density of new tree seedlings. *Assessment: unknown effectiveness (effectiveness 40%; certainty 25%; harms 23%).*

http://www.conservationevidence.com/actions/1246

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Encourage leaf litter development in new planting

## 5.10.6 Increase soil fertility



## **Likely to be beneficial**

## **Use vegetation removal together with mechanical disturbance to the soil**

Three studies, including one replicated, randomized, controlled study, in Portugal and France found that vegetation removal together with mechanical disturbance of the soil increased the cover or diversity of understory plants, or density of young trees. One of the studies found it decreased understory shrub cover. *Assessment: Likely to be beneficial (effectiveness 61%; certainty 40%; harms 15%).*

http://www.conservationevidence.com/actions/1274

#### **Trade-off between benefit and harms**

## **Add organic matter**

One of two studies, including one replicated, randomized, controlled study, in Brazil and Costa Rica found that adding leaf litter increased species richness of young trees. One found it decreased young tree density in artificial forest gaps and both found no effect on the density of tree regenerations under intact forest canopy. One of two replicated, controlled study in Portugal and the USA found that adding plant material increased total plant cover. One found mixed effects on cover depending on plant group. *Assessment: trade-offs between benefits and harms (effectiveness 45%; certainty 43%; harms 28%).*

http://www.conservationevidence.com/actions/1250

### **Use fertilizer**

Six of eight studies, including five replicated, randomized, controlled, in Europe, Brazil, Australia and the USA found that applying fertilizer

#### *Forest Conservation*

increased total plant cover, understory plant biomass, size of young trees, biomass of grasses or cover of artificially seeded plant species. Five of the studies found no effect on plant biomass, cover, seedling abundance, tree growth or tree seedling diversity. *Assessment: trade-offs between benefits and harms (effectiveness 55%; certainty 65%; harms 25%).*

http://www.conservationevidence.com/actions/1248

#### **Use soil scarification or ploughing to enhance germination**

Two studies, including one replicated, randomized, controlled study, in Portugal and the USA found that ploughing increased the cover or diversity of understory plants. Two of five studies, including two replicated, randomized, controlled, in Canada, Brazil, Ethiopia and Sweden found that ploughing increased the density of young trees. One found a decrease in density and two found mixed effects depending on tree species. One replicated, before-and-after trial in Finland found that ploughing decreased the cover of plants living on wood surface. One replicated, controlled study in the USA found that ploughing did not decrease the spreading distance and density of invasive grass seedlings. *Assessment: unknown effectiveness (effectiveness 60%; certainty 50%; harms 25%).*

http://www.conservationevidence.com/actions/1251

#### **Unknown effectiveness (limited evidence)**

#### **Add lime to the soil to increase fertility**

One replicated, randomized controlled study in the USA found that adding lime increased vegetation cover. *Assessment: unknown effectiveness (effectiveness 80%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/1249

## **Use soil disturbance to enhance germination (excluding scarification or ploughing)**

Two replicated, controlled studies in Canada and Finland found that disturbance of the forest floor decreased understory vegetation cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 35%; harms 40%).*

#### **Likely to be ineffective or harmful**

#### **Enhance soil compaction**

Two of three studies, including two replicated, randomized, controlled studies in Canada and the USA found that soil compaction increased understory plant cover and density. Two found it decreased tree regeneration height or density and understory plant species richness. *Assessment: likely to be ineffective or harmful (effectiveness 28%; certainty 40%; harms 45%).*

# 5.11 Actions to improve survival and growth rate of planted trees

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions to improve the survival and growth rate of planted trees?**



## **Beneficial**

## **Prepare the ground before tree planting**

Six of seven studies, including five replicated, randomized, controlled studies, in Canada and Sweden found that ground preparation increased the survival or growth rate of planted trees. One study found no effect of creating mounds on frost damage to seedlings. *Assessment: beneficial (effectiveness 78%; certainty 73%; harms 0%).*

http://www.conservationevidence.com/actions/1263

### **Use mechanical thinning before or after planting**

Five of six studies, including two replicated, randomized, controlled studies, in Brazil, Canada, Finland, France and the USA found that thinning trees after planting increased survival or size of planted trees. One study found mixed effects on survival and size and one found it decreased their density. One replicated study in the USA found that seedling survival rate increased with the size of the thinned area. *Assessment: beneficial (effectiveness 75%; certainty 63%; harms 10%).*

http://www.conservationevidence.com/actions/1261

### **Likely to be beneficial**

### **Fence to prevent grazing after tree planting**

Four of five studies, including two replicated, randomized, controlled studies, in Finland, Australia, Canada and the USA found that using fences

to exclude grazing increased the survival, size or cover of planted trees. Two studies found no effect on survival rate and one found mixed effects on planted tree size. *Assessment: Likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/1254

#### **Use herbicide after tree planting**

Two of three studies, including two replicated, randomized, controlled studies, in Sweden and the USA found that using herbicide increased the size of planted trees. One study found no effect. One replicated, randomized, controlled study in Sweden found no effect of using herbicide on frost damage to seedlings. *Assessment: unlikely to be beneficial (effectiveness 58%; certainty 45%; harms 0%).*

http://www.conservationevidence.com/actions/1262

#### **Trade-off between benefit and harms**

#### **Use prescribed fire after tree planting**

Two of four studies, including one replicated, randomized, controlled study, in Finland, France and the USA found that using prescribed fire after planting increased the survival and sprouting rate of planted trees. One study found fire decreased planted tree size and one found no effect on the size and survival rate. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 43%; harms 20%).*

http://www.conservationevidence.com/actions/1255

#### **Unknown effectiveness (limited evidence)**

#### **Apply insecticide to protect seedlings from invertebrates**

One randomized, replicated, controlled study in the USA found that applying insecticide increased tree seedling emergence and survival. *Assessment: unknown effectiveness (effectiveness 70%; certainty 13%; harms 0%).*

## **Add lime to the soil after tree planting**

One of two replicated, randomized, controlled studies in the USA found that adding lime before restoration planting decreased the survival of pine seedlings. One found no effect on seedling growth. *Assessment: unknown effectiveness (effectiveness 0%; certainty 30%; harms 50%).*

http://www.conservationevidence.com/actions/1259

## **Add organic matter after tree planting**

Two replicated, randomized, controlled studies in the USA found that adding organic matter before restoration planting increased seedling biomass, but decreased seedling emergence or survival. *Assessment: unknown effectiveness (effectiveness 20%; certainty 25%; harms 50%).*

http://www.conservationevidence.com/actions/1258

### **Cover the ground with straw after tree planting**

One replicated, randomized, controlled study in the Czech Republic found that covering the ground with straw, but not bark or fleece, increased the growth rate of planted trees and shrubs. *Assessment: unknown effectiveness (effectiveness 75%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1266

## **Improve soil quality after tree planting (excluding applying fertilizer)**

Two randomized, replicated, controlled studies in Australia found that different soil enhancers had mixed or no effects on tree seedling survival and height, and no effect on diameter or health. *Assessment: unknown effectiveness (effectiveness 25%; certainty 23%; harms 13%).*

http://www.conservationevidence.com/actions/1153

## **Manage woody debris before tree planting**

One replicated, randomized, controlled study in Canada found that removing woody debris increased the survival rate of planted trees. One replicated, controlled study in the USA found mixed effects on the size of planted trees. *Assessment: unknown effectiveness (effectiveness 40%; certainty 25%; harms 13%).*

#### **Use shading for planted trees**

One replicated, controlled study in Panama found that shading increased the survival rate of planted native tree seedlings. *Assessment: unknown effectiveness (effectiveness 85%; certainty 23%; harms 0%).*

http://www.conservationevidence.com/actions/1269

## **Use tree guards or shelters to protect planted trees**

One replicated, randomized, controlled study in the USA found that using light but not dark coloured plastic tree shelters increased the survival rate of planted tree seedlings. One replicated, controlled study in Hong Kong found that tree guards increased tree height after 37 but not 44 months. *Assessment: unknown effectiveness (effectiveness 60%; certainty 28%; harms 20%).*

http://www.conservationevidence.com/actions/1268

#### **Use weed mats to protect planted trees**

One replicated, controlled study in Hong Kong found no effect of using weed mats on seedling height. *Assessment: unknown effectiveness (effectiveness 0%; certainty 18%; harms 0%).*

http://www.conservationevidence.com/actions/1267

#### **Water seedlings**

One replicated, randomized, controlled study in Spain found that watering seedlings increased or had no effect on seedling emergence and survival, depending on habitat and water availability. *Assessment: unknown effectiveness (effectiveness 45%; certainty 20%; harms 0%).*

http://www.conservationevidence.com/actions/1154

#### **Unlikely to be beneficial**

### **Mechanically remove understory vegetation after tree planting**

Four of five studies, including three replicated, randomized, controlled studies in France, Sweden, Panama, Canada and the USA found no effect of controlling understory vegetation on the emergence, survival, growth rate or frost damage of planted seedlings. One found that removing shrubs increased the growth rate and height of planted seedlings, and another that removing competing herbs increased seedling biomass. *Assessment: unlikely to be beneficial (effectiveness 20%; certainty 50%; harms 0%).*

http://www.conservationevidence.com/actions/1256

## **Use different planting or seeding methods**

Four studies, including one replicated, randomized study, in Australia, Brazil, Costa Rica and Mexico found no effect of planting or seeding methods on the size and survival rate of seedlings. One replicated, controlled study in Brazil found that planting early succession pioneer tree species decreased the height of other planted species. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 43%; harms 13%).*

http://www.conservationevidence.com/actions/1264

### **Use fertilizer after tree planting**

Two of five studies, including two randomized, replicated, controlled studies, in Canada, Australia, France and Portugal found that applying fertilizer after planting increased the size of the planted trees. Three studies found no effect on the size, survival rate or health of planted trees. One randomized, replicated, controlled study in Australia found that soil enhancers including fertilizer had mixed effects on seedling survival and height. *Assessment: unlikely to be beneficial (effectiveness 38%; certainty 45%; harms 3%).*

http://www.conservationevidence.com/actions/1260

#### **No evidence found (no assessment)**


# 5.12 Education and awareness raising

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions to improve education and awareness raising?**


#### **No evidence found (no assessment)**


# 6. PEATLAND CONSERVATION

*Global evidence for the effects of interventions to conserve peatland vegetation*

#### **Nigel G. Taylor, Patrick Grillas & William J. Sutherland**

#### **Expert assessors**

**Stephanie Boudreau**, Canadian Sphagnum Peat Moss Association, Canada **Emma Goodyer**, IUCN UK Peatlands Programme, UK **Laura Graham**, Borneo Orangutan Survival Foundation, Indonesia **Richard Lindsay**, University of East London, UK **Edgar Karofeld**, University of Tartu, Estonia **David Locky**, MacEwan University, Canada **Nancy Ockendon**, University of Cambridge, UK **Anabel Rial**, Independent Consultant & IUCN Species Survival Commission, Colombia **Sarah Ross**, Penny Anderson Associates, UK **Nigel Taylor**, Tour du Valat, France **Tim Thom**, Yorkshire Peat Partnership, UK **Jennie Whinam**, University of Tasmania, Australia

**Scope of assessment**: for the conservation of vegetation in wet peatlands, including bogs, fens, fen meadows and tropical peat swamps. The focus is on overall communities and habitat-defining species, rather than rare species.

#### **Assessed:** 2018.

**Effectiveness measure** is the median % score. How effective is the intervention at conserving peatland vegetation in the collated evidence?

**Certainty measure** is the median % certainty for the effectiveness score across all peatlands that are appropriate targets of the intervention, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score. Are there any negative side effects of the intervention, on peatland vegetation, in the collated evidence?

Each **effectiveness category** assumes that the aims of the intervention match your management goals. For example, planting trees/shrubs is likely to be beneficial assuming that you want to create forested/shrubby peatland. This might not be a desirable outcome on all peatland types or in all locations.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target habitat for each intervention. The assessment may therefore refer to different habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target habitats or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 6.1 Threat: Residential and commercial development


#### **No evidence found (no assessment)**


# 6.2 Threat: Agriculture and aquaculture

## 6.2.1 Multiple farming systems


### **Unknown effectiveness (limited evidence)**

### **Retain/create habitat corridors in farmed areas**


## **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Implement 'mosaic management' of agriculture.

# 6.2.2 Wood and pulp plantations

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for wood and pulp plantations? Likely to be beneficial** ● Cut/remove/thin forest plantations ● Cut/remove/thin forest plantations and rewet peat

## **Likely to be beneficial**

## **Cut/remove/thin forest plantations**


## **Cut/remove/thin forest plantations and rewet peat**


## 6.2.3 Livestock farming and ranching

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for livestock farming and ranching?**


#### **Likely to be beneficial**

#### **Exclude or remove livestock from degraded peatlands**

• *Plant community composition:* Of two replicated, paired, controlled studies in bogs in the UK, one found that excluding sheep had no effect on the plant community. The other found that excluding sheep only affected the community in drier areas of the bog, favouring plants typically found on dry moorlands.

#### *Peatland Conservation*


#### **Unknown effectiveness (limited evidence)**

#### **Reduce intensity of livestock grazing**


https://www.conservationevidence.com/actions/1735

#### **No evidence found (no assessment)**


# 6.3 Threat: Energy production and mining


### **Unknown effectiveness (limited evidence)**

### **Replace blocks of vegetation after mining or peat extraction**


• *Assessment: unknown effectiveness – limited evidence (effectiveness 60%; certainty 35%; harms 10%). Based on evidence from: bogs (one study); fens (one study).*

https://www.conservationevidence.com/actions/1738

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Retain/create habitat corridors in areas of energy production or mining.

# 6.4 Threat: Transportation and service corridors


### **Unknown effectiveness (limited evidence)**

#### **Maintain/restore water flow across service corridors**


https://www.conservationevidence.com/actions/1741

#### **No evidence found (no assessment)**


# 6.5 Threat: Biological resource use


#### **Unknown effectiveness (limited evidence)**


**Reduce intensity of harvest**

## **No evidence found (no assessment)**


# 6.6 Threat: Human intrusions and disturbance


### **Unknown effectiveness (limited evidence)**

### **Physically exclude vehicles from peatlands**


• *Assessment: unknown effectiveness – limited evidence (effectiveness 70%; certainty 35%; harms 0%). Based on evidence from: fens (one study).*

https://www.conservationevidence.com/actions/1750

## **No evidence found (no assessment)**


# 6.7 Threat: Natural system modifications

## 6.7.1 Modified water management


### **Beneficial**

## **Rewet peatland (raise water table)**

• *Plant community composition:* Ten of thirteen studies reported that rewetting affected the overall plant community composition. Six before-and-after studies (four also replicated) in peatlands in Finland, Hungary, Sweden, Poland and Germany reported development of wetland- or peatland-characteristic communities following rewetting. One replicated, paired, controlled study in the Czech Republic found differences between rewetted and drained parts of a bog. Three site comparison studies in Finland and Canada reported differences between rewetted and natural peatlands. In contrast, three replicated studies in peatlands in the UK and fens in Germany reported that rewetting typically had no effect, or insignificant effects, on the plant community.


reported that rewetted peatlands had greater herb cover (total or sedges/rushes) than natural peatlands.


## **Unknown effectiveness (limited evidence)**

## **Irrigate peatland**


https://www.conservationevidence.com/actions/1859

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 6.7.2 Modified vegetation management


#### **Likely to be beneficial**

## **Cut/mow herbaceous plants to maintain or restore disturbance**


### **Cut large trees/shrubs to maintain or restore disturbance**


#### **Trade-off between benefit and harms**

 **Use grazing to maintain or restore disturbance**


## **Unknown effectiveness (limited evidence)**

## **Remove plant litter to maintain or restore disturbance**


#### **Use prescribed fire to maintain or restore disturbance**


# 6.7.3 Modified wild fire regime


#### **No evidence found (no assessment)**


# 6.8 Threat: Invasive and other problematic species

*This section includes evidence for the effects of interventions on peatland vegetation overall. Studies that only report effects on the target problematic species are, or will be, summarized in separate chapters (like Chapter 10).*

## 6.8.1 All problematic species


## **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Implement biosecurity measures to prevent introductions of problematic species.

# 6.8.2 Problematic plants



#### **Trade-off between benefit and harms**

### **Use prescribed fire to control problematic plants**


controlled studies in the bogs in Germany and fens in the USA found that burning, sometimes along with other interventions, had no effect on cover of other woody plants.


https://www.conservationevidence.com/actions/1774

#### **Unknown effectiveness (limited evidence)**

#### **Physically remove problematic plants**


moss from a drained area increased plant species richness, but that there was no effect in a wetter area.

• *Assessment: unknown effectiveness – limited evidence (effectiveness 48%; certainty 35%; harms 12%). Based on evidence from: fens (three studies).* https://www.conservationevidence.com/actions/1768

## **Use cutting/mowing to control problematic herbaceous plants**


https://www.conservationevidence.com/actions/1770

### **Change season/timing of cutting/mowing**

• *Plant community composition:* One replicated, randomized, paired, before-and after study in a fen meadow in the UK reported that changes in plant community composition over time were similar in spring-, summer- and autumn-mown plots. One study in a peatland in the Netherlands reported that summer- and winter-mown areas developed different plant community types.


https://www.conservationevidence.com/actions/1771

#### **Use cutting to control problematic large trees/shrubs**


## **Use herbicide to control problematic plants**


https://www.conservationevidence.com/actions/1776

#### **Introduce an organism to control problematic plants**


https://www.conservationevidence.com/actions/1777

#### **No evidence found (no assessment)**


## 6.8.3 Problematic animals


#### **Unknown effectiveness (limited evidence)**

#### **Exclude wild herbivores using physical barriers**


https://www.conservationevidence.com/actions/1860

#### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Control populations of wild herbivores.

# 6.9.1 Multiple sources of pollution

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for multiple sources of pollution?**


#### **Likely to be beneficial**

### **Divert/replace polluted water source(s)**

• *Characteristic plants:* One study in a fen in the Netherlands found that after a nutrient-enriched water source was replaced, along with other interventions to reduce pollution, cover of mosses characteristic of low nutrient levels increased.


#### **Unknown effectiveness (limited evidence)**

#### **Clean waste water before it enters the environment**


https://www.conservationevidence.com/actions/1778

## **Slow down input water to allow more time for pollutants to be removed**


## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 6.9.2 Agricultural and aquacultural effluents

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for agricultural/aquacultural effluents?**


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 6.9.3 Industrial and military effluents

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for industrial and military effluents? No evidence found (no assessment)** ● Remove oil from contaminated peatlands

### **No evidence found (no assessment)**

We have captured no evidence for the following intervention:

• Remove oil from contaminated peatlands.

## 6.9.4 Airborne pollutants


#### **Unknown effectiveness (limited evidence)**

## **Remove pollutants from waste gases before they enter the environment**


https://www.conservationevidence.com/actions/1789

### **Add lime to reduce acidity and/or increase fertility**


## **Drain/replace acidic water**


# 6.10 Threat: Climate change and severe weather


## **No evidence found (no assessment)**


# 6.11 Habitat creation and restoration

*Remember, the effectiveness category for each intervention assumes that the aims of the intervention match your management goals. You should consider whether each intervention is necessary and appropriate in your focal peatland.*

## 6.11.1 General habitat creation and restoration


## **Likely to be beneficial**

### **Restore/create peatland vegetation (multiple interventions)**

• *Plant community composition:* One replicated, controlled, before-andafter study in the UK reported that the overall plant community composition differed between restored and unrestored bogs. One replicated, controlled, site comparison study in Estonia found that restored and natural bogs contained more similar plant communities than unrestored and natural bogs. However, one site comparison study in Canada reported that after five years, bogs being restored as fens contained a different plant community to natural fens.


#### **Restore/create peatland vegetation using the moss layer transfer technique**

• *Plant community composition:* One replicated study in bogs in Canada reported that the majority of restored areas developed a community of bog-characteristic plant species within eleven years. One controlled, before-and-after study in a bog in Canada reported that a restored area (included in the previous study) developed a more peatland-characteristic plant community over time, and relative to an unrestored area.

#### *Peatland Conservation*


https://www.conservationevidence.com/actions/1804

# 6.11.2 Modify physical habitat only


### **Likely to be beneficial**

## **Fill/block ditches to create conditions suitable for peatland plants**


https://www.conservationevidence.com/actions/1805

#### **Remove upper layer of peat/soil**


#### **Unknown effectiveness (limited evidence)**

#### **Excavate pools**

• *Plant community composition:* One replicated, before-and-after, site comparison study in bogs in Canada reported that excavated pools were colonized by some peatland vegetation over 4–6 years, but contained different plant communities to natural pools. In particular, cattail *Typha latifolia* was more common in created pools.


https://www.conservationevidence.com/actions/1806

#### **Reprofile/relandscape peatland**


https://www.conservationevidence.com/actions/1807

### **Disturb peatland surface to encourage growth of desirable plants**

• *Plant community composition:* Two replicated, paired, controlled, before-and-after studies (one also randomized) in fens in Germany and Sweden reported that soil disturbance affected development of the plant community over 2–3 years. In Germany, disturbed plots developed greater cover of weedy species from the seed bank than undisturbed plots. In Sweden, the community in disturbed and undisturbed plots became less similar over time.


## **Add inorganic fertilizer**


https://www.conservationevidence.com/actions/1812

### **Cover peatland with organic mulch**

• *Vegetation cover:* One replicated, randomized, paired, controlled, before-and-after study in a bog (being restored as a fen) in Canada found that mulching bare peat did not affect cover of fen-characteristic plants. One replicated, controlled, before-and-after study in a bog in Australia reported that plots mulched with straw had similar *Sphagnum* moss cover to unmulched plots.


https://www.conservationevidence.com/actions/1813

#### **Cover peatland with something other than mulch**


https://www.conservationevidence.com/actions/1814

#### **Stabilize peatland surface to help plants colonize**


https://www.conservationevidence.com/actions/1815

#### **Build artificial bird perches to encourage seed dispersal**

• *Vegetation cover:* One replicated, paired, controlled study in a peat swamp forest in Indonesia found that artificial bird perches had no significant effect on tree seedling abundance.

• *Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 20%; harms 1%). Based on evidence from: tropical peat swamps (one study).*

https://www.conservationevidence.com/actions/1817

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 6.11.3 Introduce peatland vegetation


## **Beneficial**

#### **Add mosses to peatland surface**

• *Sphagnum moss cover:* Eleven studies in bogs in the UK, Canada, Finland and Germany and fens in the USA reported that *Sphagnum*  moss was present, after 1–4 growing seasons, in at least some plots sown with *Sphagnum*. Cover ranged from negligible to >90%. Six of these studies were controlled and found that there was more *Sphagnum* in sown than unsown plots. One additional study in Canada found that adding *Sphagnum* to bog pools did not affect *Sphagnum* cover.


#### **Add mixed vegetation to peatland surface**


• *Assessment: beneficial (effectiveness 78%; certainty 68%; harms 1%). Based on evidence from: bogs (eighteen studies).*

https://www.conservationevidence.com/actions/1822

### **Likely to be beneficial**

## **Directly plant peatland mosses**


https://www.conservationevidence.com/actions/1818

## **Directly plant peatland herbs**


#### **Directly plant peatland trees/shrubs**


https://www.conservationevidence.com/actions/1820

#### **Introduce seeds of peatland herbs**


## **Introduce seeds of peatland trees/shrubs**


reported that plots sown with shrub (and herb) seeds developed greater total vegetation cover than unsown plots after two years. One site comparison study in bogs in Estonia reported that sowing shrub seeds, along with fertilization, had no effect on total vegetation cover after 25 years.


# 6.12 Actions to complement planting


## **Likely to be beneficial**

### **Cover peatland with organic mulch (after planting)**


https://www.conservationevidence.com/actions/1828

### **Cover peatland with something other than mulch (after planting)**

• *Germination:* One replicated, controlled, before-and-after study in a bog in Germany reported mixed effects of fleece and fibre mats on germination of sown herb and shrub seeds (positive or no effect, depending on species).

#### *Peatland Conservation*


https://www.conservationevidence.com/actions/1829

#### **Reprofile/relandscape peatland (before planting)**


reprofiled and raised plots developed similar cover of other mosses/ bryophytes and vascular plants.

• *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 5%). Based on evidence from: bogs (four studies).*

https://www.conservationevidence.com/actions/1833

#### **Trade-off between benefit and harms**

#### **Add inorganic fertilizer (before/after planting)**


#### **Unknown effectiveness (limited evidence)**

#### **Introduce nurse plants (to aid focal peatland plants)**


https://www.conservationevidence.com/actions/1830

#### **Irrigate peatland (before/after planting)**


https://www.conservationevidence.com/actions/1832

#### **Create mounds or hollows (before planting)**


#### **Add fresh peat to peatland (before planting)**


https://www.conservationevidence.com/actions/1837

## **Remove vegetation that could compete with planted peatland vegetation**


https://www.conservationevidence.com/actions/1840

#### **Add root-associated fungi to plants (before planting)**


## **Likely to be ineffective or harmful**

## **Add lime (before/after planting)**


https://www.conservationevidence.com/actions/1825

#### **No evidence found (no assessment)**


# 6.13 Habitat protection


### **Likely to be beneficial**

## **Legally protect peatlands**


#### *Peatland Conservation*


https://www.conservationevidence.com/actions/1796

## **Unknown effectiveness (limited evidence)**

#### **Pay landowners to protect peatlands**


https://www.conservationevidence.com/actions/1799

### **Increase 'on the ground' protection (e.g. rangers)**


https://www.conservationevidence.com/actions/1800

#### **No evidence found (no assessment)**


# 6.14 Education and awareness


#### **Unknown effectiveness (limited evidence)**

#### **Raise awareness amongst the public (general)**


## **Provide education or training programmes about peatlands or peatland management**


https://www.conservationevidence.com/actions/1848

#### **Lobby, campaign or demonstrate to protect peatlands**


https://www.conservationevidence.com/actions/1849

#### **No evidence found (no assessment)**


# 7. PRIMATE CONSERVATION

**Jessica Junker, Hjalmar S. Kühl, Lisa Orth, Rebecca K. Smith, Silviu O. Petrovan & William J. Sutherland**

#### **Expert assessors**

**Graham L. Banes**, University of Wisconsin-Madison, USA **Sergio Marrocoli**, Max Planck Institute for Evolutionary Anthropology, Germany **Sarah Papworth**, Royal Holloway University of London, UK **Silviu O. Petrovan**, University of Cambridge, UK **Andrew J. Plumptre**, Wildlife Conservation Society, Uganda **Ricardo Rocha**, University of Cambridge, UK **Joanna M. Setchell**, Durham University, UK **Kathy Slater**, Operation Wallacea, UK **Erin Wessling**, Max Planck Institute for Evolutionary Anthropology, Germany **Liz Williamson**, University of Stirling, UK **Scope of assessment**: for wild primate species across the world.

**Assessed**: 2017.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects to the group of species of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

> Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 7.1 Threat: Residential and commercial development


#### **Likely to be beneficial**

#### **Remove and relocate 'problem' animals**

Three studies, including one replicated, before-and-after trial, in India, Kenya, the Republic of Congo and Gabon found that most primates survived the translocation. One study found that all translocated rhesus monkeys remained at the release site for at least four years. Another study showed that after 16 years, 66% of olive baboons survived and survival rate was similar to wild study groups. The third study showed that 84% of gorillas released in the Republic of Congo and Gabon survived for at least four years. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 10%).*

## **No evidence found (no assessment)**


# 7.2 Threat: Agriculture



## **Likely to be beneficial**

### **Humans chase primates using random loud noise**

One controlled, replicated, before-and-after study in Indonesia found that in areas where noise deterrents were used, along with tree nets, crop raiding by orangutans was reduced. One study in the Democratic Republic Congo found that chasing gorillas and using random noise resulted in the return of gorillas from plantation to areas close to protected forest. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Prohibit (livestock) farmers from entering protected areas**

One before-and-after site comparison study in Rwanda found that numbers of young gorillas increased after removal of cattle from a protected area, alongside other interventions. One before-and-after study in Rwanda, Uganda, and the Democratic Republic of Congo found that gorilla numbers declined following the removal of livestock, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1432

#### **Use nets to keep primates out of fruit trees**

A controlled, replicated, before-and-after study in Indonesia found that areas where nets were used to protect crop trees, crop-raiding by orangutans was reduced. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 30%; harms 20%).*

https://www.conservationevidence.com/actions/1442

#### **No evidence found (no assessment)**


# 7.3 Threat: Energy production and mining


### **No evidence found (no assessment)**


# 7.4 Threat: Transportation and service corridors


## **Likely to be beneficial**

## **Install rope or pole (canopy) bridges**

One before-and-after study in Belize study found that howler monkey numbers increased after pole bridges were constructed over man-made gaps. Two studies in Brazil and Madagascar found that primates used pole bridges to cross roads and pipelines. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1457

#### **No evidence found (no assessment)**


## 7.5.1 Hunting



## **Likely to be beneficial**

## **Conduct regular anti-poaching patrols**

Two of three studies found that gorilla populations increased after regular anti-poaching patrols were conducted, alongside other interventions. One study in Ghana found a decline in gorilla populations. One review on gorillas in Uganda found that no gorillas were killed after an increase in anti-poaching patrols. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1471

#### **Regularly de-activate/remove ground snares**

One of two studies found that the number of gorillas increased in an area patrolled for removing snares, alongside other interventions. One study in the Democratic Republic of Congo, Rwanda, and Uganda found that gorilla populations declined despite snare removal. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1475

## **Provide better equipment (e.g. guns) to anti-poaching ranger patrols**

Two studies in the Democratic Republic of Congo and Rwanda found that gorilla populations increased after providing anti-poaching guards with better equipment, alongside other interventions. One study in Uganda found that no gorillas were killed after providing game guards with better equipment. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

## **Implement local no-hunting community policies/ traditional hunting ban**

Four studies, one of which had multiple interventions, in the Democratic Republic of Congo, Belize, Cameroon and Nigeria found that primate populations increased in areas where there were bans on hunting or where hunting was reduced due to local taboos. One study found that very few primates were killed in a sacred site in China where it is forbidden to kill wildlife. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1478

## **Implement community control of patrolling, banning hunting and removing snares**

Two site comparison studies found that there were more gorillas and chimpanzees in an area managed by a community conservation organisation than in areas not managed by local communities and community control was more effective at reducing illegal primate hunting compared to the nearby national park. A before-and-after study in Cameroon found that no incidents of gorilla poaching occurred over three years after implementation of community control and monitoring of illegal activities. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1482

## **Unknown effectiveness (limited evidence)**

## **Strengthen/support/re-install traditions/taboos that forbid the killing of primates**

One site comparison study in Laos found that Laotian black crested gibbons occurred at higher densities in areas where they were protected by a local hunting taboo compared to sites were there was no taboo. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 10%; harms 0%).*

## **Implement monitoring surveillance strategies (e.g. SMART) or use monitoring data to improve effectiveness of wildlife law enforcement patrols**

One before-and-after study in Nigeria found that more gorillas and chimpanzees were observed after the implementation of law enforcement and a monitoring system. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1481

#### **Provide training to anti-poaching ranger patrols**

Two before-and-after studies in Rwanda and India found that primate populations increased in areas where anti-poaching staff received training, alongside other interventions. Two studies in Uganda and Cameroon found that no poaching occurred following training of anti-poaching rangers, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 70%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1477

#### **No evidence found (no assessment)**


# 7.5.2 Substitution


## **Unknown effectiveness (limited evidence)**

## **Use selective logging instead of clear-cutting**

One of two site comparison studies in Africa found that primate abundance was higher in forests that had been logged at low intensity compared to forest logged at high intensity. One study in Uganda found that primate abundances were similar in lightly and heavily logged forests. One study in Madagascar found that the number of lemurs increased following selective logging. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 35%; harms 30%).*

https://www.conservationevidence.com/actions/1485

## **Avoid/minimize logging of important food tree species for primates**

One before-and-after study in Belize found that black howler monkey numbers increased over a 13 year period after trees important for food for the species were preserved, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1494

#### **No evidence found (no assessment)**


# 7.6 Threat: Human intrusions and disturbance


**Unknown effectiveness (limited evidence)**

## **Implement a 'no-feeding of wild primates' policy**

A controlled before-and-after study in Japan found that reducing food provisioning of macaques progressively reduced productivity and reversed population increases and crop and forest damage. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 20%; harms 0%).*

## **Put up signs to warn people about not feeding primates**

One review study in Japan found that after macaque feeding by tourists was banned and advertised, the number of aggressive incidents between people and macaques decreased as well as the number of road collisions with macaques that used to be fed from cars. *Assessment: unknown effectiveness limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1507

## **Resettle illegal human communities (i.e. in a protected area) to another location**

One review on gorillas in Uganda found that no more gorillas were killed after human settlers were relocated outside the protected area, alongside other interventions. One before-and-after study in the Republic of Congo found that most reintroduced chimpanzees survived over five years after human communities were resettled, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 65%; certainty 15%; harms 0%).*

https://www.conservationevidence.com/actions/1515

#### **No evidence found (no assessment)**


# 7.7 Threat: Natural system modifications


#### **No evidence found (no assessment)**


# 7.8 Threat: Invasive and other problematic species and genes

## 7.8.1 Problematic animal/plant species and genes


## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 7.8.2 Disease transmission

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for disease transmission?**



## **Trade-off between benefit and harms**

## **Preventative vaccination of habituated or wild primates**

Three before-and-after studies in the Republic of Congo and Gabon, two focusing on chimpanzees and one on gorillas, found that most reintroduced individuals survived over 3.5-10 years after being vaccinated, alongside other interventions. One before-and-after study in Puerto Rico found that annual mortality of introduced rhesus macaques decreased after a preventive tetanus vaccine campaign, alongside other interventions. *Assessment: trade-offs between benefits and harms (effectiveness 70%; certainty 40%; harms 30%).*

#### **Unknown effectiveness (limited evidence)**

## **Wear face-masks to avoid transmission of viral and bacterial diseases to primates**

One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being visited by researchers and visitors wearing face-masks, alongside other interventions. One study in Uganda found that a confiscated chimpanzee was successfully reunited with his mother after being handled by caretakers wearing face-masks, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 5%; harms 0%).*

https://www.conservationevidence.com/actions/1537

#### **Keep safety distance to habituated animals**

One before-and-after study in the Republic of Congo found that most reintroduced chimpanzees survived over five years while being routinely followed from a safety distance, alongside other interventions. One beforeand-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being routinely visited from a safety distance, alongside other interventions. However, one study in Malaysia found that orangutan numbers declined while being routinely visited from a safety distance. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1538

#### **Limit time that researchers/tourists are allowed to spend with habituated animals**

One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being routinely visited during limited time, alongside other interventions. One controlled study in Indonesia found that the behaviour of orangutans that spent limited time with caretakers was more similar to the behaviour of wild orangutans than that of individuals that spent more time with caretakers. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

## **Implement quarantine for primates before reintroduction/ translocation**

Six studies, including four before-and-after studies, in Brazil, Madagascar, Malaysia and Indonesia have found that most reintroduced primates did not survive or their population size decreased over periods ranging from months up to seven years post-release, despite being quarantined before release, alongside other interventions. However, two before-andafter studies in Indonesia, the Republic of Congo and Gabon found that most orangutans and gorillas that underwent quarantine survived over a period ranging from three months to 10 years. One before-and-after study in Uganda found that one reintroduced chimpanzee repeatedly returned to human settlements after being quarantined before release alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1541

#### **Ensure that researchers/tourists are up-to-date with vaccinations and healthy**

One before-and-after study in Rwanda, Uganda and the Republic of Congo found that gorilla numbers increased while being visited by healthy researchers and visitors, alongside other interventions. However, one controlled study in Malaysia found that orangutan numbers decreased despite being visited by healthy researchers and visitors, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1546

#### **Regularly disinfect clothes, boots etc.**

One controlled, before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being regularly visited by researchers and visitors whose clothes were disinfected, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

#### **Treat sick/injured animals**

Eight studies, including four before-and-after studies, in Brazil, Malaysia, Liberia, the Democratic Republic of Congo, The Gambia and South Africa found that most reintroduced or translocated primates that were treated when sick or injured, alongside other interventions, survived being released and up to at least five years. However, five studies, including one review and four before-and-after studies, in Brazil, Thailand, Malaysia and Madagascar found that most reintroduced or translocated primates did not survive or their numbers declined despite being treated when sick or injured, alongside other interventions. One study in Uganda found that several infected gorillas were medically treated after receiving treatment, alongside other interventions. One study in Senegal found that one chimpanzee was reunited with his mother after being treated for injuries, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1550

#### **Remove/treat external/internal parasites to increase reproductive success/survival**

Five studies, including four before-and-after studies, in the Republic of Congo, The Gambia and Gabon found that most reintroduced or translocated primates that were treated for parasites, alongside other interventions, survived periods of at least five years. However, four studies, including one before-and-after study, in Brazil, Gabon and Vietnam found that most reintroduced primates did not survive or their numbers declined after being treated for parasites, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 5%; harms 0%).*

https://www.conservationevidence.com/actions/1551

#### **Conduct veterinary screens of animals before reintroducing/translocating them**

Twelve studies, including seven before-and-after studies, in Brazil, Malaysia, Indonesia, Liberia, the Republic of Congo, Guinea, Belize, French Guiana and Madagascar found that most reintroduced or translocated primates that underwent pre-release veterinary screens, alongside other interventions, survived, in some situations, up to at least five years or increased in population size. However, 10 studies, including six beforeand-after studies, in Brazil, Malaysia, French Guiana, Madagascar, Kenya, South Africa and Vietnam found that most reintroduced or translocated primates did not survive or their numbers declined after undergoing pre-release veterinary screens, alongside other interventions. One beforeand-after study in Uganda, found that one reintroduced chimpanzee repeatedly returned to human settlements after undergoing pre-release veterinary screens, alongside other interventions. One controlled study in Indonesia found that gibbons that underwent pre-release veterinary screens, alongside other interventions, behaved similarly to wild gibbons. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1553

## **Implement continuous health monitoring with permanent vet on site**

One controlled, before-and-after study in Rwanda, Uganda and the Republic of Congo found that numbers of gorillas that were continuously monitored by vets, alongside other interventions, increased over 41 years. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1554

## **Detect and report dead primates and clinically determine their cause of death to avoid disease transmission**

One controlled, before-and-after study in Rwanda, Uganda and the Republic of Congo found that numbers of gorillas that were continuously monitored by vets, alongside other interventions, increased over 41 years. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

#### **No evidence found (no assessment)**


# 7.9 Threat: Pollution

## 7.9.1 Garbage/solid waste


#### **No evidence found (no assessment)**


## 7.9.2 Excess energy


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Reduce noise pollution by restricting development activities to certain times of the day/night.

# 7.10 Education and Awareness


### **Unknown effectiveness (limited evidence)**

### **Educate local communities about primates and sustainable use**

One before-and-after study in Cameroon found that numbers of drills increased after the implementation of an education programme, alongside one other intervention. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 0%; harms 0%).*

#### **Involve local community in primate research and conservation management**

One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers decreased despite the implementation of an environmental education programme, alongside other interventions. However, one before-and-after study in Cameroon found that gorilla poaching stopped after the implementation of a community-based monitoring scheme, alongside other interventions. One before-and-after study in Belize found that numbers of howler monkeys increased while local communities were involved in the management of the sanctuary, alongside other interventions. One before-and-after study in Uganda found that a reintroduced chimpanzee repeatedly returned to human settlements despite the involvement of local communities in the reintroduction project, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1565

#### **Regularly play TV and radio announcements to raise primate conservation awareness**

One before-and-after study in Congo found that most reintroduced chimpanzees whose release was covered by media, alongside other interventions, survived over five years. *Assessment: unknown effectiveness limited evidence (effectiveness 50%; certainty 5%; harms 0%).*

https://www.conservationevidence.com/actions/1569

#### **Implement multimedia campaigns using theatre, film, print media, and discussions**

Three before-and-after studies in Belize and India found that primate numbers increased after the implementation of education programs, alongside other interventions. Three before-and-after studies found that the knowledge about primates increased after the implementation of education programmes. One before-and-after study in Madagascar found that lemur poaching appeared to have ceased after the distribution of conservation books in schools. One study in four African countries found that large numbers of people were informed about gorillas through multimedia campaigns using theatre and film. *Assessment: unknown effectiveness limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1571

#### **No evidence found (no assessment)**


# 7.11 Habitat protection

## 7.11.1 Habitat protection


#### **Likely to be beneficial**

## **Create/protect habitat corridors**

One before-and-after study in Belize found that howler monkey numbers increased after the protection of a forest corridor, alongside other interventions. *Assessment: likely to be beneficial (effectiveness 65%; certainty 41%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Legally protect primate habitat**

Two reviews and a before-and-after study in China found that primate numbers increased or their killing was halted after their habitat became legally protected, alongside other interventions. However, one beforeand-after study in Kenya found that colobus and mangabey numbers decreased despite the area being declared legally protected, alongside other interventions. Two before-and-after studies found that most chimpanzees and gorillas reintroduced to areas that received legal protection, alongside other interventions, survived over 4–5 years. However, one before-and-after study in Brazil found that most golden lion tamarins did not survive over seven years despite being reintroduced to a legally protected area, alongside other interventions, yet produced offspring that partly compensated the mortality. One controlled, site comparison study in Mexico found that howler monkeys in protected areas had lower stress levels than individuals living in unprotected forest fragments. *Assessment: unknown effectiveness limited evidence (effectiveness 60%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1578

## **Establish areas for conservation which are not protected by national or international legislation (e.g. private sector standards and codes)**

Two before-and-after studies in Rwanda, Republic of Congo and Belize found that gorilla and howler monkey numbers increased after the implementation of a conservation project funded by a consortium of organizations or after being protected by local communities, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1579

## **Create/protect forest patches in highly fragmented landscapes**

One before-and-after study in Belize found that howler monkey numbers increased after the protection of forest along property boundaries and across cleared areas, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).* https://www.conservationevidence.com/actions/1581

### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 7.11.2 Habitat creation or restoration

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for habitat creation or restoration?**


**Unknown effectiveness (limited evidence)**

## **Plant indigenous trees to re-establish natural tree communities in clear-cut areas**

One site comparison study in Kenya found that group densities of two out of three primate species were lower in planted forests than in natural forests. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 5%; harms 0%).*

## **No evidence found (no assessment)**


# 7.12.1 Species management

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for species management?**


## **Likely to be beneficial**

## **Guard habituated primate groups to ensure their safety/ well-being**

One study in Rwanda, Uganda and the Congo found that a population of mountain gorillas increased after being guarded against poachers, alongside other interventions. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Habituate primates to human presence to reduce stress from tourists/researchers etc.**

Two studies in Central Africa and Madagascar found that primate populations increased or were stable following habituation to human presence, alongside other interventions. One study in Brazil found that golden lion tamarin populations declined following habituation to human presence, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 20%; harms 10%).*

https://www.conservationevidence.com/actions/1519

### **Implement legal protection for primate species under threat**

Three of four studies in India, South East Asia, and West Africa found that primate populations declined after the respective species were legally protected, alongside other interventions. One of four studies in India found that following a ban on export of rhesus macaques, their population increased. One study in Malaysia found that a minority of introduced gibbons survived after implementing legal protection, along with other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1524

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Implement birth control to stabilize primate community/population size.

# 7.12.2 Species recovery


#### **Unknown effectiveness (limited evidence)**

## **Regularly and continuously provide supplementary food to primates**

Two of four studies found that primate populations increased after regularly providing supplementary food, alongside other interventions, while two of four studies found that populations declined. Four of four studies found that the majority of primates survived after regularly providing supplementary food, alongside other interventions. One study found that introduced lemurs had different diets to wild primates after regularly being providing supplementary food, along with other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 60%).*

https://www.conservationevidence.com/actions/1526

## **Regularly provide supplementary food to primates during resource scarce periods only**

Two studies found that the majority of primates survived after supplementary feeding in resource scarce periods, alongside other

#### *Primate Conservation*

interventions. One study in Madagascar found that the diet of introduced lemurs was similar to that of wild lemurs after supplementary feeding in resource scarce periods, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 10%).*

https://www.conservationevidence.com/actions/1527

## **Provide supplementary food for a certain period of time only**

Six of eleven studies found that a majority of primates survived after supplementary feeding, alongside other interventions. Five of eleven studies found that a minority of primates survived. One of two studies found that a reintroduced population of primates increased after supplementary feeding for two months immediately after reintroduction, alongside other interventions. One study found that a reintroduced population declined. Two studies found that abandoned primates rejoined wild groups after supplementary feeding, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 0%; harms 0%).*

https://www.conservationevidence.com/actions/1528

## **Provide additional sleeping platforms/nesting sites for primates**

One study found that a translocated golden lion tamarin population declined despite providing artificial nest boxes, alongside other interventions. One of two studies found that the majority of gorillas survived for at least seven years after nesting platforms were provided, alongside other interventions. One of two studies found that a minority of tamarins survived for at least seven years after artificial nest boxes were provided, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 0%; harms 0%).*

https://www.conservationevidence.com/actions/1530

#### **Provide artificial water sources**

Three of five studies found that a minority of primates survived for between 10 months and seven years when provided with supplementary water, alongside other interventions. Two of five studies found that a majority of primates survived for between nine and ten months, when provided with supplementary water, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1531

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 7.12.3 Species reintroduction


### **Likely to be beneficial**

## **Reintroduce primates into habitat where the species is absent**

One of two studies found that primate populations increased after reintroduction into habitat where the species was absent, alongside other interventions. One study in Thailand found that lar gibbon populations declined post-reintroduction. One study in Indonesia found that a orangutan population persisted for at least four years after reintroduction. Eight of ten studies found that a majority of primates survived after reintroduction into habitat where the species was absent, alongside other interventions. Two studies in Malaysia and Vietnam found that a minority of primates survived after reintroduction into habitat where the species was absent, alongside other interventions. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1590

#### **Unknown effectiveness (limited evidence)**

### **Translocate (capture and release) wild primates from development sites to natural habitat elsewhere**

Four studies found that the majority of primates survived following translocation from a development site to natural habitat, alongside other interventions. One study in French Guyana found that a minority of primates survived for at least 18 months. One study in India found that rhesus macaques remained at sites where they were released following translocation from a development site to natural habitat, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 30%; harms 10%).*

https://www.conservationevidence.com/actions/1558

#### **Translocate (capture and release) wild primates from abundant population areas to non-inhabited environments**

One study in Belize found that he majority of howler monkeys survived for at least 10 months after translocation from abundant population areas to an uninhabited site, along with other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1559

## **Allow primates to adapt to local habitat conditions for some time before introduction to the wild**

Two of three studies found that primate populations declined despite allowing individuals to adapt to local habitat conditions before introduction into the wild, along with other interventions. One study in Belize found an increase in introduced howler monkey populations. Ten of 17 studies found that a majority of primates survived after allowing them to adapt to local habitat conditions before introduction into the wild, along with other interventions. Six studies found that a minority of primates survived and one study found that half of primates survived. One study found that a reintroduced chimpanzee repeatedly returned to human settlements after allowing it to adapt to local habitat conditions before introduction into the wild, along with other interventions. One study found that after allowing time to adapt to local habitat conditions, a pair of reintroduced Bornean agile gibbons had a similar diet to wild gibbons. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1564

#### **Reintroduce primates in groups**

Two of four studies found that populations of introduced primates declined after reintroduction in groups, alongside other interventions, while two studies recorded increases in populations. Two studies found that primate populations persisted for at least five to 55 years after reintroduction in groups, alongside other interventions. Seven of fourteen studies found that a majority of primates survived after reintroduction in groups, alongside other interventions. Seven of fourteen studies found that a minority of primates survived after reintroduction in groups, alongside other interventions. One study found that introduced primates had a similar diet to a wild population. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).*

## **Reintroduce primates as single/multiple individuals**

Three of four studies found that populations of reintroduced primates declined after reintroduction as single/multiple individuals, alongside other interventions. One study in Tanzania found that the introduced chimpanzee population increased in size. Three of five studies found that a minority of primates survived after reintroduction as single/multiple individuals, alongside other interventions. One study found that a majority of primates survived and one study found that half of primates survived. Two of two studies in Brazil and Senegal found that abandoned primates were successfully reunited with their mothers after reintroduction as single/ multiple individuals, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1589

## **Reintroduce primates into habitat where the species is present**

One of two studies found that primate populations increased after reintroduction into habitat where the species was absent, alongside other interventions. One study in Malaysia found that an introduced orangutan population declined post-reintroduction. One study found that a primate population persisted for at least four years after reintroduction. Eight of ten studies found that a majority of primates survived after reintroduction into habitat where the species was absent, alongside other interventions. Two studies found that a minority of primates survived after reintroduction into habitat where the species was present, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1591

## **Reintroduce primates into habitat with predators**

Eight of fourteen studies found that a majority of reintroduced primates survived after reintroduction into habitat with predators, alongside other interventions. Six studies found that a minority of primates survived. One study found that an introduced primate population increased after reintroduction into habitat with predators, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1593

#### **Reintroduce primates into habitat without predators**

One study in Tanzania found that a population of reintroduced chimpanzees increased over 16 years following reintroduction into habitat without predators. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 5%; harms 0%).*

https://www.conservationevidence.com/actions/1592

## 7.12.4 *Ex-situ* conservation


**Unknown effectiveness (limited evidence)**

## **Captive breeding and reintroduction of primates into the wild: born and reared in cages**

One study in Brazil found that the majority of reintroduced golden lion tamarins which were born and reared in cages, alongside other interventions, did not survive over seven years.

#### *Primate Conservation*

Two of two studies in Brazil and French Guiana found that more reintroduced primates that were born and reared in cages, alongside other interventions, died post-reintroduction compared to wild-born monkeys. *Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 15%; harms 0%).*

https://www.conservationevidence.com/actions/1594

## **Captive breeding and reintroduction of primates into the wild: limited free-ranging experience**

One of three studies found that the majority of captive-bred primates, with limited free-ranging experience and which were reintroduced in the wild, alongside other interventions, had survived. One study in Madagascar found that a minority of captive-bred lemurs survived reintroduction over five years. One study found that reintroduced lemurs with limited freeranging experience had a similar diet to wild primates. Reintroduction was undertaken alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1595

## **Captive breeding and reintroduction of primates into the wild: born and raised in a free-ranging environment**

One study in Brazil found that the majority of golden lion tamarins survived for at least four months after being raised in a free-ranging environment, alongside other interventions. One study found that the diet of lemurs that were born and raised in a free-ranging environment alongside other interventions, overlapped with that of wild primates. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1596

### **Rehabilitate injured/orphaned primates**

Six of eight studies found that the majority of introduced primates survived after rehabilitation of injured or orphaned individuals, alongside other interventions. One study found that a minority of introduced primates survived, and one study found that half of primates survived. One of two studies found that an introduced chimpanzee population increased in size after rehabilitation of injured or orphaned individuals, alongside other interventions. One study found that an introduced rehabilitated or injured primate population declined. One review found that primates living in sanctuaries had a low reproduction rate. One study found that introduced primates had similar behaviour to wild primates after rehabilitation of injured or orphaned individuals, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1597

#### **Fostering appropriate behaviour to facilitate rehabilitation**

Three of five studies found that a minority of primates survived after they were fostered to encourage behaviour appropriate to facilitate rehabilitation, alongside other interventions. Two studies found that the majority of reintroduced primates fostered to facilitate rehabilitation along other interventions survived. Three studies found that despite fostering to encourage behaviour appropriate to facilitate rehabilitation, alongside other interventions, primates differed in their behaviour to wild primates. *Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%; harms 0%).*

# 7.13 Livelihood; economic and other incentives

7.13.1 Provide benefits to local communities for sustainably managing their forest and its wildlife


#### **Unknown effectiveness (limited evidence)**

## **Provide monetary benefits to local communities for sustainably managing their forest and its wildlife (e.g. REDD, employment)**

One before-and-after study in Belize found that howler monkey numbers increased after the provision of monetary benefits to local communities alongside other interventions. However, one before-and-after study in Rwanda, Uganda and the Congo found that gorilla numbers decreased despite the implementation of development projects in nearby communities, alongside other interventions. One before-and-after study in Congo found that most chimpanzees reintroduced to an area where local communities received monetary benefits, alongside other interventions, survived over five years. *Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 25%; harms 0%).*

https://www.conservationevidence.com/actions/1509

## **Provide non-monetary benefits to local communities for sustainably managing their forest and its wildlife (e.g. better education, infrastructure development)**

One before-and-after study India found that numbers of gibbons increased in areas were local communities were provided alternative income, alongside other interventions. One before-and-after study in Congo found that most chimpanzees reintroduced survived over seven years in areas where local communities were provided non-monetary benefits, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).*

# 7.13.2 Long-term presence of research/tourism project

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for the long-term presence of research-/ tourism project?**


## **Likely to be beneficial**

## **Run research project and ensure permanent human presence at site**

Three before-and-after studies, in Rwanda, Uganda, Congo and Belize found that numbers of gorillas and howler monkeys increased while populations were continuously monitored by researchers, alongside other interventions. One before-and-after study in Kenya found that troops of translocated baboons survived over 16 years post-translocation while being continuously monitored by researchers, alongside other interventions. One before-and-after study in the Congo found that most reintroduced chimpanzees survived over 3.5 years while being continuously monitored by researchers, alongside other interventions. However, one beforeand-after study in Brazil found that most reintroduced tamarins did not survive over 7 years, despite being continuously monitored by researchers, alongside other interventions; but tamarins reproduced successfully. One review on gorillas in Uganda found that no individuals were killed while gorillas were continuously being monitored by researchers, alongside other interventions. *Assessment: likely to be beneficial (effectiveness 61%; certainty 40%; harms 0%).*

#### **Trade-off between benefit and harms**

#### **Run tourism project and ensure permanent human presence at site**

Six studies, including four before-and-after studies, in Rwanda, Uganda, Congo and Belize found that numbers of gorillas and howler monkeys increased after local tourism projects were initiated, alongside other interventions. However, two before-and-after studies in Kenya and Madagascar found that numbers of colobus and mangabeys and two of three lemur species decreased after implementing tourism projects, alongside other interventions. One before-and-after study in China found that exposing macaques to intense tourism practices, especially through range restrictions to increase visibility for tourists, had increased stress levels and increased infant mortality, peaking at 100% in some years. *Assessment: trade-off between benefit and harms (effectiveness 40%; certainty 40%; harms 40%).*

https://www.conservationevidence.com/actions/1512

#### **Unknown effectiveness (limited evidence)**

#### **Permanent presence of staff/managers**

Two before-and-after studies in the Congo and Gabon found that most reintroduced chimpanzees and gorillas survived over a period of between nine months to five years while having permanent presence of reserve staff. One before-and-after study in Belize found that numbers of howler monkeys increased after permanent presence of reserve staff, alongside other interventions. However, one before-and-after study in Kenya found that numbers of colobus and mangabeys decreased despite permanent presence of reserve staff, alongside other interventions. *Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 30%; harms 0%).*

# 8. SHRUBLAND AND HEATHLAND CONSERVATION

**Philip A. Martin, Ricardo Rocha, Rebecca K. Smith & William J. Sutherland**

**Expert assessors**

**Andrew Bennet**, La Trobe University, Australia **Brian van Wilgen**, Stellenbosch University, South Africa **Rob Marrs**, University of Liverpool, UK **Chris Diek**, Royal Society for the Protection of Birds, UK **G. Matt Davies**, Ohio State University, USA **David Le Maitre**, CSIR, UK **Giles Groome**, Consultant Ecologist, UK **Isabel Barrio**, University of Iceland, Iceland **James Adler**, Surrey Wildlife Trust, UK **Jon Keeley**, US Geological Survey, Western Ecological Research Center and Department of Ecology and Evolutionary Biology, University of California, USA **Jonty Denton**, Consultant Ecologist, UK **Penny Anderson**, Penny Anderson Associates Limited, UK

**Scope of assessment:** for the conservation of shrubland and heathland habitats (not specific species within these habitats).

**Assessed:** 2017.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects on the shrubland and heathland habitats of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target habitat for each intervention. The assessment may therefore refer to different habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target habitats or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 8.1 Threat: Residential and commercial development


#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Remove residential or commercial development

areas

• Maintain/create habitat corridors in developed areas.

# 8.2 Threat: Agriculture and aquaculture

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of agriculture and aquaculture in shrublands and heathlands?**


## **Beneficial**

#### **Reduce number of livestock**

Two before-and-after trials in the UK and South Africa and one replicated, controlled study in the UK found that reducing or stopping grazing increased the abundance or cover of shrubs. Two site comparison studies in the UK found that cover of common heather declined in sites with high livestock density, but increased in sites with low livestock density. One site comparison study in the Netherlands found that dwarf shrub cover was higher in ungrazed sites. One replicated, randomized, before-and-after study in Spain found that reducing grazing increased the cover of western gorse. One randomized, controlled trial and one before-and-after trial in the USA found that stopping grazing did not increase shrub abundance. One site comparison study in France found that ungrazed sites had higher cover of ericaceous shrubs, but lower cover of non-ericaceous shrubs than grazed sites. One site comparison study in the UK found that reducing grazing had mixed effects on shrub cover. One replicated, randomized, controlled study in the UK found that reducing grazing increased vegetation height. However, one replicated, controlled, paired, site comparison study in the UK found that reducing grazing led to a reduction in the height of heather plants. Two site comparison studies in France and the Netherlands found that ungrazed sites had a lower number of plant species than grazed sites. One replicated, controlled, paired, site comparison study in Namibia and South Africa found that reducing livestock numbers increased plant cover and the number of plant species. One controlled study in Israel found that reducing grazing increased plant biomass. However, one randomized, site comparison on the island of Gomera, Spain found that reducing grazing did not increase plant cover and one replicated, controlled study in the UK found that the number of plant species did not change . One replicated, controlled study in the UK found no change in the cover of rush or herbaceous species as a result of a reduction in grazing. Two site comparison studies in France and the Netherlands found that grass cover and sedge cover were lower in ungrazed sites than in grazed sites. One randomized, controlled study in the USA found a mixed effect of reducing grazing on grass cover. *Assessment: Beneficial (effectiveness 65%, certainty 70%, harms 10%).*

https://www.conservationevidence.com/actions/1607

#### **Likely to be beneficial**

#### **Use fences to exclude livestock from shrublands**

Two replicated, controlled, randomized studies (one of which was also a before-and-after trial) and one controlled before-and-after trial in the UK found that using fences to exclude livestock increased shrub cover or abundance. Two replicated, controlled, randomized studies in Germany and the UK found that using fences increased shrub biomass or the biomass and height of individual heather plants. Two controlled studies (one of which was a before-and-after study) in Denmark and the UK found that heather presence or cover was higher in fenced areas that in areas that were not fenced. However, one site comparison study in the USA found that using fences led to decreased cover of woody plants. Three replicated, controlled studies (one of which was a before and after study) in the USA and the UK found that fencing either had a mixed effect on shrub cover or did not alter shrub cover. One randomized, replicated, controlled, paired study in the UK found that using fences to exclude livestock did not alter the number of plant species, but did increase vegetation height and biomass. One controlled, before-and-after study in the UK found that fenced areas had lower species richness than unfenced areas. One randomized, replicated, controlled, before-and-after trial in the UK and one site comparison study in the USA found that using fences to exclude livestock led to a decline in grass cover. However, four controlled studies (one of which a beforeand-after trial) in the USA, the UK, and Finland found that using fences did not alter cover of grass species. One site comparison study in the USA and one replicated, controlled study in the UK recorded an increase in grass cover. One controlled study in Finland found that using fences to exclude livestock did not alter the abundance of herb species and one site comparison in the USA found no difference in forb cover between fenced and unfenced areas. One replicated, controlled study in the USA found fencing had a mixed effect on herb cover. A*ssessment: likely to be beneficial (effectiveness 51%; certainty 60%; harms 10%).*

https://www.conservationevidence.com/actions/1545

#### **Unknown effectiveness (limited evidence)**

#### **Change type of livestock**

Two replicated, before-and-after studies and one controlled study in Spain and the UK found changing the type of livestock led to mixed effects on shrub cover. However, in two of these studies changing the type of livestock reduced the cover of herbaceous species. One replicated, controlled, beforeand-after study in the UK found that grazing with both cattle and sheep, as opposed to grazing with sheep, reduced cover of purple moor grass, but had no effect on four other plant species. A*ssessment: unknown effectiveness (effectiveness 40%; certainty 29%; harms 5%).*

#### **Shorten the period during which livestock can graze**

One replicated, controlled, before-and-after study in the UK found that shortening the period in which livestock can graze had mixed effects on heather, bilberry, crowberry, and grass cover. One replicated, randomized, controlled study in the UK found that grazing in only winter or summer did not affect the heather or grass height compared to year-round grazing. A*ssessment: unknown effectiveness (effectiveness 32%; certainty 20%; harms 2%).*

# 8.3 Threat: Energy production and mining


### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Maintain/create habitat corridors in areas of energy production or mining.

# 8.4 Threat: Biological resource use

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of biological resource use in shrublands and heathlands?**


#### **No evidence found (no assessment)**


# 8.5 Threat: Transportation and service corridors


## **No evidence found (no assessment)**


# 8.6 Threat: Human intrusions and disturbance

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of human intrusions and disturbance in shrublands and heathlands?**


**Unknown effectiveness (limited evidence)**

## **Re-route paths to reduce habitat disturbance**

One before-and-after trial in Australia found that closing paths did not alter shrub cover, but did increase the number of plant species in an alpine shrubland. *Assessment: unknown effectiveness (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1619

#### **No evidence found (no assessment)**


# 8.7 Threat: Natural system modifications

## 8.7.1 Modified fire regime


### **No evidence found (no assessment)**


## 8.7.2 Modified vegetation management


#### **Unknown effectiveness (limited evidence)**

#### **Reinstate the use of traditional burning practices**

One before and after study in the UK found that prescribed burning initially decreased the cover of most plant species, but that their cover subsequently increased. A systematic review of five studies from the UK found that prescribed burning did not alter species diversity. A replicated, controlled study in the UK found that regeneration of heather was similar in cut and burned areas. A systematic review of five studies, from Europe found that prescribed burning did not alter grass cover relative to heather cover. *Assessment: unknown effectiveness (effectiveness 40%; certainty 30%; harms 12%).*

https://www.conservationevidence.com/actions/1625

#### **Use cutting/mowing to mimic grazing**

One systematic review of three studies in lowland heathland in North Western Europe found that mowing did not alter heather abundance relative to grass abundance. A site comparison in Italy found that mowing increased heather cover. Two replicated, randomized, before-and-after trials in Spain (one of which was controlled) found that using cutting to mimic grazing reduced heather cover. One replicated, randomized, controlled, beforeand-after trial in Spain found that cutting increased the number of plant species. However, a replicated, randomized, before-and-after trial found that the number of plant species only increased in a minority of cases. One replicated, randomized, before-and-after trial in Spain found that cutting to mimic grazing increased grass cover. A site comparison in Italy found that mowing increased grass cover. One site comparison study in Italy found a reduction in tree cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 25%; harms 10%).*

https://www.conservationevidence.com/actions/1627

#### **Increase number of livestock**

Two site comparison studies in the UK found that cover of common heather declined in sites with a high density of livestock. One site comparison in the Netherlands found that dwarf shrub cover was lower in grazed areas than in ungrazed areas. One before-and-after study in Belgium found that grazing increased cover of heather. One site comparison in France found that areas grazed by cattle had higher cover of non-ericaceous shrubs, but lower cover of ericaceous shrubs. One before-and-after study in the Netherlands found that increasing the number of livestock resulted in an increase in the number of common heather and cross-leaved heath seedlings. One randomized, replicated, paired, controlled study in the USA found that increasing the number of livestock did not alter shrub cover. One replicated, site comparison study and one before-and-after study in the UK and Netherlands found that increasing grazing had mixed effects on shrub and heather cover. Three site comparisons in France, the Netherlands and Greece found that grazed areas had a higher number of plant species than ungrazed areas. One before-and-after study in Belgium found that the number of plant species did not change after the introduction of grazing. One replicated, before-and-after study in the Netherlands found a decrease in the number of plant species. One before-and-after study in the Netherlands found that increasing the number of livestock resulted in a decrease in vegetation height. One replicated, before-and-after trial in France found that grazing to control native woody species increased vegetation cover in one of five sites but did not increase vegetation cover in four of five sites. A systematic review of four studies in North Western Europe found that increased grazing intensity increased the cover of grass species, relative to heather species. One before-and-after study and two site comparisons in the Netherlands and France found areas with high livestock density had higher grass and sedge cover than ungrazed areas. One randomized, replicated, paired, controlled study in the USA found that increasing the number of livestock reduced grass and herb cover. One before-and-after study in Spain found that increasing the number of ponies in a heathland site reduced grass height. One replicated, site comparison in the UK and one replicated before-and-after study in the Netherlands found that increasing cattle had mixed effects on grass and herbaceous species. *Assessment: unknown effectiveness (effectiveness 30%; certainty 30%; harms 20%).*

# 8.8 Threat: Invasive and other problematic species

## 8.8.1 Problematic tree species

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of invasive and other problematic tree species in shrublands and heathlands?**


### **Unknown effectiveness (limited evidence)**

## **Apply herbicide to trees**

One replicated, controlled, before-and-after study in South Africa found that using herbicide to control trees increased plant diversity but did not increase shrub cover. One randomized, replicated, controlled study in the UK found that herbicide treatment of trees increased the abundance of common heather seedlings. *Assessment: unknown effectiveness (effectiveness 40%; certainty 35%; harms 10%).*

https://www.conservationevidence.com/actions/1629

#### **Cut trees**

One randomized, replicated, controlled study in the UK found that cutting birch trees increased density of heather seedlings but not that of mature common heather plants. One replicated, controlled study in South Africa found that cutting non-native trees increased herbaceous plant cover but did not increase cover of native woody plants. One site comparison study in South Africa found that cutting non-native Acacia trees reduced shrub and tree cover. *Assessment: unknown effectiveness (effectiveness 37%; certainty 30%; harms 3%).*

https://www.conservationevidence.com/actions/1630

#### **Cut trees and remove leaf litter**

One before-and-after trial in the Netherlands found that cutting trees and removing the litter layer increased the cover of two heather species and of three grass species. *Assessment: unknown effectiveness (effectiveness 45%; certainty 10%; harms 3%).*

https://www.conservationevidence.com/actions/1631

#### **Cut trees and remove seedlings**

A controlled, before-and-after study in South Africa found that cutting orange wattle trees and removing seedlings of the same species increased plant diversity and shrub cover. *Assessment: unknown effectiveness (effectiveness 62%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1632

#### **Use prescribed burning to control trees**

One randomized, replicated, controlled, before-and-after trial in the USA found that burning to control trees did not change cover of two of three grass species. One randomized, controlled study in Italy found that prescribed burning to control trees reduced cover of common heather, increased cover of purple moor grass, and had mixed effects on the basal area of trees. *Assessment: unknown effectiveness (effectiveness 10%; certainty 20%; harms 22%).*

https://www.conservationevidence.com/actions/1721

### **Use grazing to control trees**

One randomized, controlled, before-and-after study in Italy found that grazing to reduce tree cover reduced cover of common heather and the basal area of trees, but did not alter cover of purple moor grass. *Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 5%).*

https://www.conservationevidence.com/actions/1634

#### **Cut trees and apply herbicide**

One controlled study in the UK found that cutting trees and applying herbicide increased the abundance of heather seedlings. However, one replicated, controlled study in the UK found that cutting silver birch trees and applying herbicide did not alter cover of common heather when compared to cutting alone. Two controlled studies (one of which was a before-and-after study) in South Africa found that cutting of trees and applying herbicide did not increase shrub cover. Two controlled studies in South Africa found that cutting trees and applying herbicide increased the total number of plant species and plant diversity. One replicated, controlled study in the UK found that cutting and applying herbicide reduced cover of silver birch trees. *Assessment: unknown effectiveness (effectiveness 45%; certainty 35%; harms 3%).*

https://www.conservationevidence.com/actions/1636

## **Cut trees and use prescribed burning**

One replicated, before-and-after trial in the USA found that cutting western juniper trees and using prescribed burning increased the cover of herbaceous plants. One replicated, randomized, controlled, before-andafter trial in the USA found that cutting western juniper trees and using prescribed burning increased cover of herbaceous plants but had no effect on the cover of most shrubs. One controlled study in South Africa found that cutting followed by prescribed burning reduced the cover of woody plants but did not alter herbaceous cover. *Assessment: unknown effectiveness (effectiveness 40%; certainty 35%; harms 5%).*

https://www.conservationevidence.com/actions/1637

## **Increase number of livestock and use prescribed burning to control trees**

One randomized, controlled, before-and-after study in Italy found that using prescribed burning and grazing to reduce tree cover reduced the cover of common heather and the basal area of trees. However, it did not alter the cover of purple moor grass. *Assessment: unknown effectiveness (effectiveness 2%; certainty 12%; harms 12%).*

https://www.conservationevidence.com/actions/1722

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 8.8.2 Problematic grass species

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of invasive and other problematic grass species in shrublands and heathlands?**



## **Unknown effectiveness (limited evidence)**

#### **Cut/mow to control grass**

One controlled study in the UK found that mowing increased the number of heathland plants in one of two sites. The same study found that the presence of a small minority of heathland plants increased, but the presence of nonheathland plants did not change. Three replicated, controlled studies in the UK and the USA found that cutting to control grass did not alter cover of common heather or shrub seedling abundance. One replicated, controlled study in the UK found that cutting to control purple moor grass reduced vegetation height, had mixed effects on purple moor grass cover and the number of plant species, and did not alter cover of common heather. Two randomized, controlled studies in the USA found that mowing did not increase the cover of native forb species. Both studies found that mowing reduced grass cover but in one of these studies grass cover recovered over time. One replicated, controlled study in the UK found that mowing did not alter the abundance of wavy hair grass relative to rotovating or cutting turf. *Assessment: unknown effectiveness (effectiveness 22%; certainty 35%; harms 5%).*

https://www.conservationevidence.com/actions/1638

### **Cut/mow to control grass and sow seed of shrubland plants**

One randomized, replicated, controlled study in the USA found that the biomass of sagebrush plants in areas where grass was cut and seeds sown did not differ from areas where grass was not cut, but seeds were sown. One randomized controlled study in the USA found that cutting grass and sowing seeds increased shrub seedling abundance and reduced grass cover One randomized, replicated, controlled study in the USA found that sowing seeds and mowing did not change the cover of non-native plants or the number of native plant species. *Assessment: unknown effectiveness (effectiveness 31%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1639

#### **Rake to control grass**

A randomized, replicated, controlled, paired study in the USA found that cover of both invasive and native grasses, as well as forbs was lower in areas that were raked than in areas that were not raked, but that the number of annual plants species did not differ. *Assessment: unknown effectiveness (effectiveness 30%; certainty 20%; harms 12%).*

https://www.conservationevidence.com/actions/1640

#### **Cut/mow and rotovate to control grass**

One controlled study in the UK found that mowing followed by rotovating increased the number of heathland plant species in one of two sites. The same study found that the presence of a minority of heathland and nonheathland species increased. *Assessment: unknown effectiveness (effectiveness 22%; certainty 15%; harms 7%).*

https://www.conservationevidence.com/actions/1641

### **Apply herbicide and sow seeds of shrubland plants to control grass**

One randomized, controlled study in the USA found that areas where herbicide was sprayed and seeds of shrubland species were sown had more shrub seedlings than areas that were not sprayed or sown with seeds. One randomized, replicated, controlled study in the USA found that spraying with herbicide and sowing seeds of shrubland species did not increase the cover of native plant species, but did increase the number of native plant species. One of two studies in the USA found that spraying with herbicide and sowing seeds of shrubland species reduced non-native grass cover. One study in the USA found that applying herbicide and sowing seeds of shrubland species did not reduce the cover of non-native grasses. *Assessment: unknown effectiveness (effectiveness 35%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1644

## **Apply herbicide and remove plants to control grass**

One randomized, replicated, controlled, paired study in the USA found that areas sprayed with herbicide and weeded to control non-native grass cover had higher cover of native grasses and forbs than areas that were not sprayed or weeded, but not a higher number of native plant species. The same study found that spraying with herbicide and weeding reduced non-native grass cover. *Assessment: unknown effectiveness (effectiveness 42%; certainty 20%; harms 2%).*

https://www.conservationevidence.com/actions/1645

#### **Use grazing to control grass**

One replicated, controlled, before-and-after study in the Netherlands found that grazing to reduce grass cover had mixed effects on cover of common heather and cross-leaved heath. One replicated, controlled, before-and-after study in the Netherlands found that cover of wavy-hair grass increased and one before-and-after study in Spain found a reduction in grass height. *Assessment: unknown effectiveness (effectiveness 32%; certainty 17%; harms 10%).*

https://www.conservationevidence.com/actions/1646

#### **Use precribed burning to control grass**

One replicated controlled, paired, before-and-after study in the UK found that prescribed burning to reduce the cover of purple moor grass, did not reduce its cover but did reduce the cover of common heather. One randomized, replicated, controlled study in the UK found that prescribed burning initially reduced vegetation height, but this recovered over time. A*ssessment: unknown effectiveness (effectiveness 0%; certainty 20%; harms 15%).*

https://www.conservationevidence.com/actions/1723

### **Cut and use prescribed burning to control grass**

One randomized, replicated, controlled, paired, before-and-after study in the UK found that burning and cutting to reduce the cover of purple moor grass reduced cover of common heather but did not reduce cover of purple moor grass. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 10%).*

https://www.conservationevidence.com/actions/1724

#### **Use herbicide and prescribed burning to control grass**

One randomized, replicated, controlled, paired, before-and-after study in the UK found that burning and applying herbicide to reduce the cover of purple moor grass reduced cover of common heather but did not reduce cover of purple moor grass. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 20%).*

https://www.conservationevidence.com/actions/1725

#### **Strip turf to control grass**

One controlled study in the UK found that cutting and removing turf increased the number of heathland plants. The same study found that the presence of a small number of heathland plants increased, and that the presence of a small number of non-heathland plants decreased. One replicated, controlled study in the UK found that presence of heather was similar in areas where turf was cut and areas that were mown or rotovated. One replicated, controlled study in the UK found that the presence of wavy hair grass was similar in areas where turf was cut and those that were mown or rotovated. *Assessment: unknown effectiveness (effectiveness 32%; certainty 25%; harms 2%).*

https://www.conservationevidence.com/actions/1647

#### **Rotovate to control grass**

One replicated, controlled study in the UK found that rotovating did not alter the presence of heather compared to mowing or cutting. The same study found that wavy hair grass presence was not altered by rotovating, relative to areas that were mown or cut. *Assessment: unknown effectiveness (effectiveness 0%; certainty 5%; harms 0%).*

https://www.conservationevidence.com/actions/1648

#### **Add mulch to control grass**

One randomized, controlled study in the USA found that areas where mulch was used to control grass cover had a similar number of shrub seedlings to areas where mulch was not applied. The same study found that mulch application did not reduce grass cover. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1649

#### **Add mulch to control grass and sow seed**

One randomized, controlled study in the USA found that adding mulch, followed by seeding with shrub seeds, increased the seedling abundance of one of seven shrub species but did not reduce grass cover. *Assessment: unknown effectiveness (effectiveness 5%; certainty 7%; harms 0%).*

https://www.conservationevidence.com/actions/1650

#### **Cut/mow, rotovate and sow seeds to control grass**

One replicated, controlled study in the UK found that rotovating did not alter the presence of heather compared to mowing or cutting. The same study found that wavy hair grass presence was not altered by rotovating, relative to areas that were mown or cut. *Assessment: unknown effectiveness (effectiveness 50%; certainty 12%; harms 1%).*

https://www.conservationevidence.com/actions/1651

#### **Unlikely to be beneficial**

#### **Use herbicide to control grass**

Two randomized, controlled studies in the UK and the USA found that spraying with herbicide did not affect the number of shrub or heathland plant seedlings. One of these studies found that applying herbicide increased the abundance of one of four heathland plants, but reduced the abundance of one heathland species. However, one randomized, controlled study in the UK found that applying herbicide increased cover of heathland species. One randomized, replicated, controlled study in the UK reported no effect on the cover of common heather. One randomized, replicated study in the UK reported mixed effects of herbicide application on shrub cover. Two randomized, controlled studies in the USA and the UK found that herbicide application did not change the cover of forb species. However, one randomized, controlled, study in the USA found that herbicide application increased native forb cover. Four of five controlled studies (two of which were replicated) in the USA found that grass cover or non-native grass cover were lower in areas where herbicides were used to control grass than areas were herbicide was not used. Two randomized, replicated, controlled studies in the UK found that herbicide reduced cover of purple moor grass, but not cover of three grass/reed species. Two randomized, controlled studies in the UK found that herbicide application did not reduce grass cover. *Assessment: unlikely to be beneficial (effectiveness 32%; certainty 40%; harms 7%).*

https://www.conservationevidence.com/actions/1643

## 8.8.3 Bracken


#### **Unknown effectiveness (limited evidence)**

#### **Use herbicide to control bracken**

One controlled, before-and-after trial in the UK found that applying herbicide to control bracken increased the number of heather seedlings. However, two randomized, controlled studies in the UK found that spraying with herbicide did not increase heather cover. One randomized, controlled study in the UK found that applying herbicide to control bracken increased heather biomass. One replicated, randomized, controlled study in the UK found that the application of herbicide increased the number of plant species in a heathland site. However, one replicated, randomized, controlled study in the UK found that spraying bracken with herbicide had no effect on species richness or diversity. One randomized, controlled study in the UK found that applying herbicide to control bracken increased the cover of wavy hair-grass and sheep's fescue. One controlled study in the UK found that applying herbicide to control bracken increased the cover of gorse and the abundance of common cow-wheat. One controlled, beforeand-after trial in the UK found that the application of herbicide reduced the abundance of bracken but increased the number of silver birch seedlings. Three randomized, controlled studies in the UK found that the application of herbicide reduced the biomass or cover of bracken. However, one controlled study in the UK found that applying herbicide did not change the abundance of bracken. *Assessment: unknown effectiveness (effectiveness 50%; certainty 35%; harms 10%).*

https://www.conservationevidence.com/actions/1652

#### **Cut to control bracken**

One randomized, controlled, before-and-after trial in Norway and one randomized, controlled study in the UK found that cutting bracken increased the cover or biomass of heather. However, two randomized, replicated, controlled studies in the UK found that cutting bracken did not increase heather cover or abundance of heather seedlings. One randomized, replicated, controlled study in the UK found that cutting to control bracken increased the species richness of heathland plant species. However, another randomized, replicated, controlled study in the UK found that cutting to control bracken did not alter species richness but did increase species diversity. One randomized, replicated, controlled study in the UK found that cutting bracken increased cover of wavy hair-grass and sheep's fescue. One controlled study in the UK found that cutting bracken did not increase the abundance of gorse or common cow-wheat. One randomized, controlled, before-and-after trial in Norway and two randomized, controlled studies in the UK found that cutting bracken reduced bracken cover or biomass. One randomized, replicated, controlled, paired study the UK found that cutting had mixed effects on bracken cover. However, one controlled study in the UK found that cutting bracken did not decrease the abundance of bracken. *Assessment: unknown effectiveness (effectiveness 50%; certainty 35%; harms 2%).*

https://www.conservationevidence.com/actions/1653

#### **Cut and apply herbicide to control bracken**

One randomized, controlled study in the UK found that cutting and applying herbicide to control bracken did not alter heather biomass. One randomized, controlled, before-and-after trial in Norway found that cutting and applying herbicide increased heather cover. One randomized, replicated, controlled, paired study in the UK found that cutting and using herbicide had no significant effect on the cover of seven plant species. One replicated, randomized, controlled study in the UK found that cutting bracken followed by applying herbicide increased plant species richness when compared with applying herbicide followed by cutting. Three randomized, controlled studies (one also a before-and-after trial, and one of which was a paired study) in the UK and Norway found that cutting and applying herbicide reduced bracken biomass or cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 30%; harms 4%).*

https://www.conservationevidence.com/actions/1654

#### **Cut bracken and rotovate**

One controlled study in the UK found that cutting followed by rotovating to control bracken did not increase total plant biomass or biomass of heather. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1656

#### **Use 'bracken bruiser' to control bracken**

One randomized, replicated, controlled, before-and-after, paired study in the UK found that bracken bruising increased bracken cover, though bracken cover also increased in areas where bracken bruising was not done .There was no effect on the number of plant species or plant diversity. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 7%).*

## **Use herbicide and remove leaf litter to control bracken**

One randomized, controlled study in the UK found that using herbicide and removing leaf litter did not increase total plant biomass after eight years. The same study found that for three of six years, heather biomass was higher in areas where herbicide was sprayed and leaf litter was removed than in areas that were sprayed with herbicide. *Assessment: unknown effectiveness (effectiveness 27%; certainty 12%; harms 2%).*

https://www.conservationevidence.com/actions/1660

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 8.8.4 Problematic animals

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of problematic animals in shrublands and heathlands?**


## **Unknown effectiveness (limited evidence)**

#### **Use fences to exclude large herbivores**

One controlled study in the USA found that using fences to exclude deer increased the height of shrubs, but not shrub cover. *Assessment: unknown effectiveness (effectiveness 7%; certainty 10%; harms 0%).*

#### **Reduce numbers of large herbivores**

One before-and-after trial in the USA found that removing feral sheep, cattle and horses increased shrub cover and reduced grass cover. One replicated study in the UK found that reducing grazing pressure by red deer increased the cover and height of common heather. *Assessment: unknown effectiveness (effectiveness 70%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1663

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Use biological control to reduce the number of problematic invertebrates.

# 8.9 Threat: Pollution

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of pollution in shrublands and heathlands?**


#### **Unknown effectiveness (limited evidence)**

#### **Mow shrubland to reduce impact of pollutants**

One randomized, replicated, controlled study in the UK found that mowing to reduce the impact of nitrogen deposition did not alter shoot length of common heather or the number of purple moor grass seedlings. One controlled study in the UK found that mowing a heathland affected by nitrogen pollution did not alter the cover or shoot length of heather compared to areas where prescribed burning was used. A*ssessment: unknown effectiveness (effectiveness 0%; certainty 17%; harms 0%).*

https://www.conservationevidence.com/actions/1669

#### **Burn shrublands to reduce impacts of pollutants**

One randomized, replicated, controlled study in the UK found that prescribed burning to reduce the impact of nitrogen deposition did not alter the shoot length of common heather or the number of purple moor grass seedlings compared to mowing. A controlled study in the UK found that burning to reduce the concentration of pollutants in a heathland affected by nitrogen pollution did not alter the cover or shoot length of heather relative to areas that were mowed. *Assessment: unknown effectiveness (effectiveness 0%; certainty 17%; harms 0%).*

https://www.conservationevidence.com/actions/1670

#### **No evidence found (no assessment)**


# 8.10 Threat: Climate change and severe weather

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for managing the impacts of climate change and severe weather in shrublands and heathlands?**


#### **No evidence found (no assessment)**



**(no assessment)** ● Legally protect habitat around shrubland

#### **No evidence found (no assessment)**


# 8.12 Habitat restoration and creation

## 8.12.1 General restoration

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for general restoration of shrubland and heathland habitats?**


## **Likely to be beneficial**

## **Allow shrubland to regenerate without active management**

Five before-and-after trials (two of which were replicated) in the USA, UK, and Norway, found that allowing shrubland to recover after fire without any active management increased shrub cover or biomass. One replicated, paired, site comparison in the USA found that sites that were allowed to recover without active restoration had similar shrub cover to unburned areas. One controlled, before-and-after trial in the USA found no increase in shrub cover. One before-and-after trial in Norway found an increase in heather height. One before-and-after trial in Spain found that there was an increase in seedlings for one of three shrub species. Two replicated, randomized, controlled, before-and-after trials in Spain and Portugal found that there was an increase in the cover of woody plant species. One before-and-after study in Spain found that cover of woody plants increased, but the number of woody plant species did not. One replicated, before-andafter study in South Africa found that the height of three protea species increased after recovery from fire. One before-and-after trial in South Africa found that there was an increase in vegetation cover, but not in the number of plant species. One before-and-after trial in South Africa found an increase in a minority of plant species. Two before-and-after trials in the USA and UK found that allowing shrubland to recover after fire without active management resulted in a decrease in grass cover or biomass. One controlled, before-and-after trial in the USA found an increase in the cover of a minority of grass species. One before-and-after study in Spain found that cover of herbaceous species declined. One replicated, before-andafter study in the UK found mixed effects on cover of wavy hair grass. One controlled, before-and-after trial in the USA found no increase in forb cover. One replicated, randomized, controlled before-and-after trial in Spain found that herb cover declined after allowing recovery of shrubland after fire. *Assessment: likely to be beneficial (effectiveness 62%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1679

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Restore/create connectivity between shrublands.

## 8.12.2 Modify physical habitat

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for restoring shrubland and heathland habitats by modifying the physical habitat?**



### **Likely to be beneficial**

#### **Add topsoil**

Two randomized, controlled studies in the UK found that the addition of topsoil increased the cover or abundance of heathland plant species. One replicated, site comparison in Spain found an increase in the abundance of woody plants. One randomized, controlled study in the UK found an increase in the number of seedlings for a majority of heathland plants. One controlled study in Namibia found that addition of topsoil increased plant cover and the number of plant species, but that these were lower than at a nearby undisturbed site. One randomized, controlled study in the UK found an increase in the cover of forbs but a reduction in the cover of grasses. *Assessment: likely to be beneficial (effectiveness 67%; certainty 45%; harms 0%).*

https://www.conservationevidence.com/actions/1686

#### **Unknown effectiveness (limited evidence)**

#### **Disturb vegetation**

One randomized, replicated, controlled study in the UK found that vegetation disturbance did not increase the abundance or species richness of specialist plants but increased the abundance of generalist plants. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 7%).*

#### **Strip topsoil**

Two randomized, replicated, controlled studies in the UK found that removal of topsoil did not increase heather cover or cover of heathland species. However, one controlled study in the UK found an increase in heather cover. One randomized, replicated, controlled study in the UK found that removing topsoil increased the cover of both specialist and generalist plant species, but did not increase species richness. One randomized, replicated, paired, controlled study in the UK found that removal of topsoil increased cover of annual grasses but led to a decrease in the cover of perennial grasses. One controlled study in the UK found that removal of turf reduced cover of wavy hair grass. One controlled, before-and-after trial in the UK found that stripping surface layers of soil increased the cover of gorse and sheep's sorrel as well as the number of plant species. *Assessment: unknown effectiveness (effectiveness 30%; certainty 25%; harms 3%).*

https://www.conservationevidence.com/actions/1685

#### **Remove leaf litter**

One randomized, controlled study in the UK found that removing leaf litter did not alter the presence of heather. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1688

#### **Add sulphur to soil**

One randomized, replicated, controlled study in the UK found that adding sulphur to the soil of a former agricultural field did not increase the number of heather seedlings in five of six cases. *Assessment: unknown effectiveness (effectiveness 2%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1691

#### **Use erosion blankets/mats to aid plant establishment**

One replicated, randomized, controlled study in the USA found that using an erosion control blanket increased the height of two shrub species. One replicated, randomized, controlled study in the USA did not find an increase in the number of shrub species, but one controlled study in China did find an increase in plant diversity following the use of erosion control blankets. The same study found an increase in plant biomass and cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1692

## **Add mulch and fertilizer to soil**

One randomized, controlled study in the USA found that adding mulch and fertilizer did not increase the seedling abundance of seven shrub species. The same study also reported no change in grass cover. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1694

## **Add manure to soil**

One replicated, randomized, controlled study in South Africa found that adding manure increased plant cover and the number of plant species. *Assessment: unknown effectiveness (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1695

#### **Irrigate degraded shrublands**

One replicated, randomized, controlled study at two sites in USA found that temporary irrigation increased shrub cover. *Assessment: unknown effectiveness (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1696

#### **No evidence found (no assessment)**


## 8.12.3 Introduce vegetation or seeds

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for restoring shrubland and heathland habitats by introducing vegetation or seeds?**


#### **Beneficial**

#### **Sow seeds**

Five of six studies (including three replicated, randomized, controlled studies, one site comparison study and one controlled study) in the UK, South Africa, and the USA found that sowing seeds of shrubland species increased shrub cover. One of six studies in the UK found no increase in shrub cover. One replicated site comparison in the USA found in sites where seed containing Wyoming big sagebrush was sown the abundance of the plant was higher than in sites where it was not sown. One replicated, randomized, controlled study in the USA found that shrub seedling abundance increased after seeds were sown. One study in the USA found very low germination of hackberry seeds when they were sown. One replicated, randomized, controlled study in the USA found that the community composition of shrublands where seeds were sown was similar to that found in undisturbed shrublands. One randomized, controlled study in the UK found an increase in the cover of heathland plants when seeds were sown. One replicated, randomized, controlled study in South Africa found that sowing seeds increased plant cover. One replicated, randomized, controlled study in the USA found that areas where seeds were sown did not differ significantly in native cover compared to areas where shrubland plants had been planted. One controlled study in the USA found higher plant diversity in areas where seeds were sown by hand than in areas where they were sown using a seed drill. Two of three studies (one of which was a replicated, randomized, controlled study) in the USA found that sowing seeds of shrubland species resulted in an increase in grass cover. One randomized, controlled study in the UK found no changes in the cover of grasses or forbs. *Assessment: beneficial (effectiveness 70%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1698

## **Unknown effectiveness (limited evidence)**

## **Plant individual plants**

One replicated, randomized, controlled study in the USA found that planting California sagebrush plants did not increase the cover of native plant species compared to sowing of seeds or a combination of planting and sowing seeds. One replicated, randomized, controlled study in South Africa found that planting *Brownanthus pseudoschlichtianus* plants increased plant cover, but not the number of plant species. One study in the USA found that a majority of planted plants survived after one year. *Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1697

## **Sow seeds and plant individual plants**

One replicated, controlled study in the USA found that planting California sagebrush and sowing of seeds did not increase cover of native plant species compared to sowing of seeds, or planting alone. *Assessment: unknown effectiveness (effectiveness 10%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1700

## **Spread clippings**

One randomized, controlled study in the UK found that the addition of shoots and seeds of heathland plants did not increase the abundance of mature plants for half of plant species. One randomized, controlled study in the UK found that the frequency of heather plants was not significantly different in areas where heather clippings had been spread and areas where they were not spread. One replicated, randomized, controlled study in the UK found an increase in the number of heather seedlings, but not of other heathland species. One randomized, controlled study in the UK found that the addition of shoots and seeds increased the number of seedlings for a minority of species. One replicated, randomized, controlled study in South Africa found that plant cover and the number of plant species did not differ significantly between areas where branches had been spread and those where branches had not been spread. *Assessment: unknown effectiveness (effectiveness 30%; certainty 32%; harms 0%).*

https://www.conservationevidence.com/actions/1701

#### **Build bird perches to encourage colonization by plants**

One replicated, controlled study in South Africa found that building artificial bird perches increased the number of seeds at two sites, but no shrubs became established at either of these sites. *Assessment: unknown effectiveness (effectiveness 10%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1702

#### **Plant turf**

Two randomized, controlled studies in the UK found that planting turf from intact heathland sites increased the abundance or cover of heathland species. One of these studies also found that planting turf increased the seedling abundance for a majority of heathland plant species. One randomized, controlled study in the UK found that planting turf increased forb cover, and reduced grass cover. One randomized, replicated, controlled study in Iceland found that planting large turves from intact heathland sites increased the number of plant species, but smaller turves did not. A*ssessment: unknown effectiveness (effectiveness 62%; certainty 30%; harms 0%).*

# 8.13 Actions to benefit introduced vegetation


### **Unknown effectiveness (limited evidence)**

#### **Add fertilizer to soil (alongside planting/seeding)**

A replicated, controlled study in Iceland found that adding fertilizer and sowing seeds increased cover of shrubs and trees in a majority of cases. The same study showed an increase in vegetation cover in two of three cases. One controlled study in the USA found that adding fertilizer increased the biomass of four-wing saltbush in a majority of cases. *Assessment: unknown effectiveness (effectiveness 45%; certainty 25%; harms 0%).*

https://www.conservationevidence.com/actions/1704

## **Add peat to soil (alongside planting/seeding)**

One replicated, randomized, controlled study in the UK found that adding peat to soil and sowing seed increased the cover of common heather in the majority of cases, compared to seeding alone. One replicated, randomized, controlled study in the UK found that adding peat to soil and sowing seed increased the density of heather seedlings, and led to larger heather plants than seeding alone, but that no seedlings survived after two years. *Assessment: unknown effectiveness (effectiveness 42%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1705

### **Add mulch and fertilizer to soil (alongside planting/ seeding)**

A randomized, controlled study in the USA found that adding mulch and fertilizer, followed by sowing of seeds increased the abundance of seedlings for a minority of shrub species. The same study found that adding mulch and fertilizer, followed by sowing seeds had no significant effect on grass cover. *Assessment: unknown effectiveness (effectiveness 35%; certainty 15%; harms 0%).*

https://www.conservationevidence.com/actions/1707

### **Add gypsum to soil (alongside planting/seeding)**

One randomized, controlled study in South Africa found that adding gypsum to soils and sowing seeds increased survival of seedlings for one of two species. *Assessment: unknown effectiveness (effectiveness 30%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1708

### **Add sulphur to soil (alongside planting/seeding)**

A randomized, replicated, controlled study in the UK found that adding sulphur to soil alongside sowing seeds did not increase heather cover in a majority of cases. One replicated, controlled study in the UK found that adding sulphur and spreading heathland clippings had mixed effects on cover of common heather, perennial rye-grass, and common bent. One randomized, controlled study in the UK found that adding sulphur to soil alongside planting of heather seedlings increased their survival, though after two years survival was very low. *Assessment: unknown effectiveness (effectiveness 20%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1710

### **Strip/disturb topsoil (alongside planting/seeding)**

Two replicated, controlled studies in the UK found that removal of topsoil and addition seed/clippings increased cover of heathland plants or cover of heather and gorse. One controlled study in the UK found that soil disturbance using a rotovator and spreading clippings of heathland plants (alongside mowing) increased the number of heathland plants. One replicated, controlled study in the UK found that stripping the surface layers of soil and adding seed reduced the cover of perennial rye-grass. One randomized, replicated, paired, and controlled study in the UK found that removal of topsoil and addition of the clippings of heathland plants did not alter the cover of annual grasses but led to a decrease in cover of perennial grasses. *Assessment: unknown effectiveness (effectiveness 60%; certainty 35%; harms 0%).*

https://www.conservationevidence.com/actions/1711

### **Add topsoil (alongside planting/seeding)**

One randomized, replicated, paired, controlled study in the USA found that addition of topsoil alongside sowing of seed increased the biomass of grasses but reduced the biomass of forbs in comparison to addition of topsoil alone. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1857

### **Plant seed balls**

A randomized, replicated, controlled study in the USA found that planting seed balls resulted in lower seedling numbers than sowing seed. *Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).*

#### **Plant/sow seeds of nurse plants alongside focal plants**

A randomized, replicated, controlled study in the UK found that sowing seeds of nurse plants and heathland plants did not increase the cover of common heather. One replicated, randomized, controlled study in the USA found that sowing seeds of nurse plants and California sagebrush seeds together reduced survival of shrubs in more than half of cases. The same study found that California sagebrush biomass was also reduced when its seeds were sown with those of nurse plants. *Assessment: unknown effectiveness (effectiveness 0%; certainty 20%; harms 10%).*

https://www.conservationevidence.com/actions/1713

#### **Plant/seed under established vegetation**

A replicated, randomized, controlled study in the USA found that sowing seed under established shrubs had mixed effects on blackbrush seedling emergence. *Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1714

#### **Plant shrubs in clusters**

A randomized, controlled study in South Africa found that when shrubs were planted in clumps more of them died than when they were planted alone. *Assessment: unknown effectiveness (effectiveness 0%; certainty 15%; harms 1%).*

https://www.conservationevidence.com/actions/1715

#### **Add root associated bacteria/fungi to introduced plants**

Two controlled studies (one of which was randomized) in Spain found that adding rhizobacteria to soil increased the biomass of shrubs. One of these studies also found an increase in shrub height. *Assessment: unknown effectiveness (effectiveness 60%; certainty 15%; harms 0%).*

# 8.14 Education and awareness

## **Based on the collated evidence, what is the current assessment of the effectiveness of interventions for education and awareness of shrubland and heathland habitats?**


### **No evidence found (no assessment)**


# 9. MANAGEMENT OF CAPTIVE ANIMALS

#### **Coral S. Jonas, Lydia T. Timbrell, Fey Young, Silviu O. Petrovan, Andrew E. Bowkett & Rebecca K. Smith**

*Husbandry interventions for captive breeding amphibians*

#### **Expert assessors**

**Kay Bradfield**, Perth Zoo, Australia **Jeff Dawson**, Durrell Wildlife Conservation Trust, UK **Devin Edmonds**, Association Mitsinjo, Madagascar **Jonathan Kolby**, Honduras Amphibian Rescue and Conservation Center, Honduras **Stephanie Jayson**, Veterinary Department, Zoological Society of London, UK **Daniel Nicholson**, Queen Mary University of London, UK **Silviu O. Petrovan**, Cambridge University, UK and Froglife Trust, UK **Jay Redbond**, Wildfowl & Wetlands Trust, UK **Rebecca K. Smith**, Cambridge University, UK **Benjamin Tapley**, Herpetology Section, Zoological Society of London, UK

**Scope of assessment**: for husbandry interventions for captive breeding amphibians.

**Assessed**: 2017.

*Promoting health and welfare in captive carnivores (felids, canids and ursids) through feeding practices*

#### **Expert assessors**

**Kathy Baker**, Whitley Wildlife Conservation Trust, Newquay Zoo, UK **Marcus Clauss**, University of Zurich, Switzerland **Ellen Dierenfeld**, Independent comparative nutrition consultant, USA **Thomas Quirke**, University College Cork, Republic of Ireland **Joanna Newbolt**, Whitley Wildlife Conservation Trust, Paignton Zoo, and University of Plymouth, UK **Simon Marsh**, Yorkshire Wildlife Wildlife Park, UK **Amy Plowman**, Whitley Wildlife Conservation Trust, Paignton Zoo, UK **Katherine Whitehouse-Tedd**, Nottingham Trent University, UK **Gwen Wirobski**, University of Veterinary Medicine Vienna, Austria

**Scope of assessment**: for promoting health and welfare in captive carnivores (felids, canids and ursids) through feeding practices.

**Assessed**: 2018.

*Promoting natural feeding behaviours in primates in captivity*

#### **Expert assessors**

**Francis Cabana**, Wildlife Reserves Singapore, Singapore **Po-Han Chou**, Taipei Zoo, Taiwan **Ellen Dierenfeld**, Independent comparative nutrition consultant, USA **Mike Downman**, Dartmoor Zoo, UK **Craig Gilchrist**, Paignton Zoo, UK **Amy Plowman**, Whitley Wildlife Conservation Trust, Paignton Zoo, UK

**Scope of assessment**: for promoting natural feeding behaviours in captive primates.

**Assessed**: 2017.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects on the species included.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

> Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 9.1 *Ex-situ* conservation – breeding amphibians

9.1.1 Refining techniques using less threatened species


### **Unknown effectiveness (limited evidence)**

## **Identify and breed a similar species to refine husbandry techniques prior to working with target species**

Two small, replicated interlinked studies in Brazil found that working with a less threatened surrogate species of frog first to establish husbandry interventions promoted successful breeding of a critically endangered species of frog. *Assessment: unknown effectiveness (effectiveness 68%; certainty 30%; harms 15%).*

## 9.1.2 Changing environmental conditions/microclimate


### **Unknown effectiveness (limited evidence)**

## **Vary enclosure temperature to simulate seasonal changes in the wild**

One small, replicated study in Italy found that one of six females bred following a drop in temperature from 20-24 to 17°C, and filling of an egg laying pond. One replicated, before-and-after study in 2006-2012 in Australia found that providing a pre-breeding cooling period, alongside allowing females to gain weight before the breeding period, along with separating sexes during the non-breeding period, providing mate choice for females and playing recorded mating calls, increased breeding success. *Assessment: unknown effectiveness (effectiveness 50%; certainty 35%; harms 0%).*

https://www.conservationevidence.com/actions/1864

## **Vary quality or quantity (UV% or gradients) of enclosure lighting to simulate seasonal changes in the wild**

One replicated study in the UK found that there was no difference in clutch size between frogs given an ultraviolet (UV) boost compared with those that only received background levels. However, frogs given the UV boost had a significantly greater fungal load than frogs that were not UV-boosted. *Assessment: unknown effectiveness (effectiveness 0%; certainty 33%; harms 20%).*

https://www.conservationevidence.com/actions/1865

## **Provide artificial aquifers for species which breed in upwelling springs**

One small study in the USA found that salamanders bred in an aquarium fitted with an artificial aquifer. *Assessment: unknown effectiveness (effectiveness 50%; certainty 15%; harms 0%).*

https://www.conservationevidence.com/actions/1871

### **Vary artificial rainfall to simulate seasonal changes in the wild**

Two replicated, before-and-after studies in Germany and Austria found that simulating a wet and dry season, as well as being moved to an enclosure with more egg laying sites and flowing water in Austria, stimulated breeding and egg deposition. In Germany, no toadlets survived past 142 days old. *Assessment: unknown effectiveness (effectiveness 78%; certainty 33%; harms 0%).*

### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 9.1.3 Changing enclosure design for spawning or egg laying sites


#### **Unknown effectiveness (limited evidence)**

#### **Provide multiple egg laying sites within an enclosure**

One replicated study in Australia found that frogs only bred once moved into an indoor enclosure which had various types of organic substrate, allowed temporary flooding, and enabled sex ratios to be manipulated along with playing recorded mating calls. One small, replicated, beforeand-after study in Fiji found that adding rotting logs and hollow bamboo pipes to an enclosure, as well as a variety of substrates, promoted egg laying in frogs. *Assessment: unknown effectiveness (effectiveness 50%; certainty 25%; harms 0%).*

https://www.conservationevidence.com/actions/1873

#### **Provide natural substrate for species which do not breed in water (e.g. burrowing/tunnel breeders)**

Two replicated studies in Australia and Fiji found that adding a variety of substrates to an enclosure, as well as rotting logs and hollow bamboo pipes in one case, promoted egg laying of frogs. The Australian study also temporarily flooded enclosures, manipulated sex ratios and played recorded mating calls. *Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1874

## **Provide particular plants as breeding areas or egg laying sites**

One small, controlled study in the USA found that salamanders bred in an aquarium heavily planted with java moss and swamp-weed. *Assessment: unknown effectiveness (effectiveness 75%; certainty 20%; harms 0%).*

# 9.1.4 Manipulate social conditions


#### **Unknown effectiveness (limited evidence)**

#### **Manipulate sex ratio within the enclosure**

One replicated study in Australia found that frogs only bred once sex ratios were manipulated, along with playing recorded mating calls and moving frogs into an indoor enclosure which allowed temporary flooding, and had various types of organic substrate. *Assessment: unknown effectiveness (effectiveness 35%; certainty 15%; harms 0%).*

https://www.conservationevidence.com/actions/1879

### **Separate sexes in non-breeding periods**

One replicated, before-and-after study in Australia found that clutch size of frogs increased when sexes were separated in the non-breeding periods, alongside providing female mate choice, playing recorded mating calls and allowing females to increase in weight before breeding. *Assessment: unknown effectiveness (effectiveness 65%; certainty 30%; harms 0%).*

### **Play recordings of breeding calls to simulate breeding season in the wild**

One replicated study in Australia found that frogs only bred when recorded mating calls were played, as well as manipulating the sex ratio after frogs were moved into an indoor enclosure that allowed temporary flooding and had various types of organic substrates. One replicated, before-and-after study in Australia found that clutch size of frogs increased when playing recorded mating calls, along with the sexes being separated in the nonbreeding periods, providing female mate choice, and allowing females to increase in weight before breeding. *Assessment: unknown effectiveness (effectiveness 35%; certainty 28%; harms 0%).*

https://www.conservationevidence.com/actions/1881

#### **Allow female mate choice**

One replicated study in Australia found that frogs only bred after females carrying eggs were introduced to males, sex ratios were manipulated, recorded mating calls were played, and after being moved to an indoor enclosure which allowed temporary flooding and had various types of organic substrates.

One replicated, before-and-after study in Australia found that clutch size of frogs increased when female mate choice was provided, alongside playing recorded mating calls, sexes being separated in the non-breeding periods, and allowing females to increase in weight before breeding. *Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).*

https://www.conservationevidence.com/actions/1882

#### **No evidence found (no assessment)**


# 9.1.5 Changing the diet of adults


## **Unknown effectiveness (limited evidence)**

## **Supplement diets with carotenoids (including for colouration)**

One study in the USA found that adding carotenoids to fruit flies fed to frogs reduced the number of clutches, but increased the number of tadpoles and successful metamorphs. *Assessment: unknown effectiveness (effectiveness 70%; certainty 28%; harms 0%).*

https://www.conservationevidence.com/actions/1887

## **Increase caloric intake of females in preparation for breeding**

One replicated, before-and-after study in Australia found that clutch size of frogs increased when females increased in weight before breeding, as well as having mate choice, recorded mating calls, and sexes being separated during the non-breeding periods. *Assessment: unknown effectiveness (effectiveness 60%; certainty 23%; harms 0%).*

https://www.conservationevidence.com/actions/1888

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 9.1.6 Manipulate rearing conditions for young

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for manipulating rearing conditions for the young Trade-off between** ● Manipulate temperature of enclosure to improve


## **Trade-off between benefit and harms**

## **Manipulate temperature of enclosure to improve development or survival to adulthood**

One replicated study in Spain found that salamander larvae had higher survival rates when reared at lower temperatures. One replicated study in Germany found that the growth rate and development stage reached by harlequin toad tadpoles was faster at a higher constant temperature rather than a lower and varied water temperature. One replicated study in Australia found that frog tadpoles took longer to reach metamorphosis when reared at lower temperatures. One replicated, controlled study in Iran found that developing eggs reared within a temperature range of 12-25°C had higher survival rates, higher growth rates and lower abnormalities than those raised outside of that range. *Assessment: trade-offs between benefits and harms (effectiveness 80%; certainty 58%; harms 20%).*

https://www.conservationevidence.com/actions/1893

#### **Unknown effectiveness (limited evidence)**

### **Formulate larval diets to improve development or survival to adulthood**

One randomized, replicated, controlled study in the USA found that tadpoles had higher body mass and reached a more advanced developmental stage when fed a control diet (rabbit chow and fish food) or freshwater algae, compared to those fed pine or oak pollen. One randomized, replicated study in Portugal found that tadpoles reared on a diet containing 46% protein had higher growth rates, survival and body weights at metamorphosis compared to diets containing less protein. *Assessment: unknown effectiveness (effectiveness 65%; certainty 35%; harms 0%).*

https://www.conservationevidence.com/actions/1889

## **Manipulate larval density within the enclosure**

One randomized study in the USA found that decreasing larval density of salamanders increased larvae survival and body mass. *Assessment: unknown effectiveness (effectiveness 88%; certainty 28%; harms 0%).*

### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 9.1.7 Artificial reproduction

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for artificial reproduction?**

**No evidence found (no assessment)** ● Use artificial cloning from frozen or fresh tissue

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:

• Use artificial cloning from frozen or fresh tissue

For summarised evidence for


See Smith, R.K. and Sutherland, W.J. (2014) *Amphibian Conservation: Global Evidence for the Effects of Interventions*. Exeter, Pelagic Publishing.

Key messages and summaries are available here:

https://www.conservationevidence.com/actions/834 https://www.conservationevidence.com/actions/883

# 9.2 Promoting health and welfare in captive carnivores (felids, canids and ursids) through feeding practices

## 9.2.1 Diet and food type


#### **Likely to be beneficial**

#### **Provide bones, hides or partial carcasses**

One replicated, before-and-after study in the USA and one replicated, controlled study in Finland found that the provision of bones decreased the frequency of stereotypic behaviours in lions, tigers and Arctic foxes. Two replicated, before-and-after studies of felids and red foxes in the USA and Norway found that the provision of bones increased activity and manipulation time. *Assessment: likely to be beneficial (effectiveness 80%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1902

#### **Trade-off between benefit and harms**

#### **Feed whole carcasses (with or without organs/ gastrointestinal tract)**

Two replicated, before-and-after studies in the USA found that feeding whole carcasses reduced pacing levels in lions, leopards, snow leopards and cougars. However, it increased pacing in tigers. One replicated, randomized, controlled study in Denmark found that when fed whole rabbit, cheetahs had lower blood protein urea, zinc and vitamin A levels compared to supplemented beef. One replicated before-and-after study in Denmark found that feeding whole rabbit showed lower levels of inflammatory bowel indicators in cheetahs. One replicated, randomized study and one controlled study in the USA found that when fed whole 1 to 3 day old chickens, ocelots had lower digestible energy and fat compared to a commercial diet and African wildcats had had lower organic matter digestibility compared to a ground-chicken diet. *Assessment: trade-offs between benefits and harms (effectiveness 80%; certainty 70%; harms 25%).*

### **Unknown effectiveness (limited evidence)**

## **Feed commercially prepared diets**

One replicated, before-and-after study in the USA found that providing a commercial diet to maned wolves led to similar dry matter intake and digestibility despite having a lower protein content. One replicated, controlled study in South Africa found that cheetahs fed a commercial diet had a similar likelihood of developing gastritis as those fed horse meat, lower levels of blood protein urea but higher levels of creatine. One study in USA found that cheetahs fed a commercial meat diet or whole chicken carcasses had plasma a-tocopherol, retinol and taurine concentrations within the ranges recommended for domestic cats. *Assessment: unknown effectiveness (effectiveness 40%; certainty 35%; harms 50%).*

https://www.conservationevidence.com/actions/1900

#### **Feed plant-derived protein**

One replicated, randomized, controlled study and one replicated, controlled study in the USA found that a plant-derived protein diet increased digestible energy and dry matter digestibility but decreased mineral retention and plasma taurine levels in maned wolves compared to a (supplemented) animal-based protein diet. *Assessment: unknown effectiveness (effectiveness 10%; certainty 25%; harms 70%).*

https://www.conservationevidence.com/actions/1903

## **Supplement meat-based diets with prebiotic plant material to facilitate digestion**

One replicated, before-and-after study in India found that providing Jerusalem artichoke as a supplement increased two types of gut microbiota, faecal scores and faecal moisture content in leopards. *Assessment: unknown effectiveness (effectiveness 50%; certainty 25%; harms 0%).*

https://www.conservationevidence.com/actions/1905

## **Supplement meat-based diet with amino acid**

One replicated, before-and-after study in the USA found that supplementing an animal-protein diet with taurine, increased plasma taurine levels in maned wolves. *Assessment: unknown effectiveness (effectiveness 90%; certainty 25%; harms 0%).*

https://www.conservationevidence.com/actions/1908

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 9.2.2 Food presentation and enrichment


### **Beneficial**

## **Hide food around enclosure**

Four replicated, before-and-after studies in the USA, UK and Germany and one before-and-after study of a black bear, leopard cats, bush dogs, maned wolves and Malayan sun bears found that hiding food increased exploring and foraging behaviours. One replicated, before-and-after study and one before-and-after study in the USA found a decrease in stereotypical pacing in leopard cats and black bear. One before-and-after study in the USA found that hiding food reduced the time Canadian lynx spent sleeping during the day. *Assessment: beneficial (effectiveness 90%; certainty 70%; harms 10%).*

https://www.conservationevidence.com/actions/1915

#### **Likely to be beneficial**

#### **Present food frozen in ice**

Two replicated, before-and-after studies in the USA found that when presented with food frozen in ice, abnormal or stereotypic behaviours decreased and activity levels increased in bears and felids. One replicated, before-and-after study in the USA found that manipulation behaviours increased in lions, whereas a replicated study in the USA found that manipulation behaviours decreased in grizzly bears. *Assessment: likely to be beneficial (effectiveness 70%; certainty 52%; harms 10%).*

https://www.conservationevidence.com/actions/1923

#### **Present food inside objects (e.g. Boomer balls)**

Two before-and-after studies in Germany and India found that exploratory and foraging behaviours increased and stereotypic behaviours decreased in sloth bears and spectacled bears when presented with food inside objects. One before-and-after study in the USA found that exploring/ foraging behaviours decreased in a sloth bear when presented with food inside objects. One replicated study in the USA found that grizzly bears spent a similar time manipulating food in a box and freely available food. *Assessment: likely to be beneficial (effectiveness 60%; certainty 70%; harms 10%).*

https://www.conservationevidence.com/actions/1924

#### **Trade-off between benefit and harms**

#### **Provide devices to simulate live prey, including sounds, lures, pulleys and bungees**

Two before-and-after studies in the USA and the UK found that activity levels and behavioural diversity increased in felids when presented with a lure or pulley system. One replicated, before-and-after study in the USA found that pacing behaviour decreased and walking increased in cougars, but pacing initially increased in tigers, when provided with a carcass on a bungee. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 50%; harms 25%).*

https://www.conservationevidence.com/actions/1927

#### **Unknown effectiveness (limited evidence)**

#### **Change location of food around enclosure**

One replicated, before-and-after study in Ireland found that altering the location of food decreased pacing behaviours in cheetahs. *Assessment: unknown effectiveness (effectiveness 90%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1918

#### **Scatter food around enclosure**

One replicated, before-and-after study in Brazil found that scattered feeding increased locomotion in maned wolves. One replicated study in Brazil found that maned wolves spent more time in the section of their enclosure with scattered food than in a section with food on a tray. *Assessment: unknown effectiveness (effectiveness 70%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1921

#### **Provide live vertebrate prey**

One small before-and-after study in the USA found that hunting behaviour increased and sleeping decreased when a fishing cat was provided with live fish. One replicated, before-and-after study in the USA found that there was no change in the occurrence of stereotypical behaviours in tigers when provided with live fish. *Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1925

#### **Provide live invertebrate prey**

One replicated study in the USA found that provision of live prey increased explorative behaviours in fennec foxes compared to other types of enrichment. *Assessment: unknown effectiveness (effectiveness 80%; certainty 20%; harms 0%).*

## **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


# 9.2.3 Feeding schedule


#### **Trade-off between benefit and harms**

### **Provide food on a random temporal schedule**

Three replicated, before-and-after studies and one replicated, controlled study found that an unpredictable feeding schedule reduced the frequency of stereotypic pacing behaviours in tigers and cheetahs. One replicated, before-and-after controlled study in the USA found that an unpredictable feeding schedule increased territorial behaviour in coyotes but did not affect travelling or foraging. One before-and-after study in Switzerland found that an unpredictable feeding schedule increased behavioural diversity in red foxes. *Assessment: trade-offs between benefits and harms (effectiveness 100%; certainty 80%; harms 20%).*

#### **Unknown effectiveness (limited evidence)**

#### **Allocate fast days**

One replicated, before-and-after study in the UK found that large felids fed once every three days paced more frequently on non-feeding days. *Assessment: unknown effectiveness (effectiveness 6%; certainty 25%; harms 50%).*

https://www.conservationevidence.com/actions/1906

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 9.2.4 Social feeding

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for social feeding?**


#### **No evidence found (no assessment)**


# 9.3 Promoting natural feeding behaviours in primates in captivity

## 9.3.1 Food Presentation


#### **Beneficial**

#### **Scatter food throughout enclosure**

Four studies, including one replicated study, in the USA, found that scattering food throughout enclosures increased overall activity, feeding and exploration and decreased abnormal behaviours and aggression. *Assessment: beneficial (effectiveness 80%; certainty 80%; harms 0%).*

https://www.conservationevidence.com/actions/1315

#### **Likely to be beneficial**

#### **Hide food in containers (including boxes and bags)**

Three studies including two before-and-after studies in the USA and Ireland found that the addition of food in boxes, baskets or tubes increased activity levels in lemurs and foraging levels in gibbons. *Assessment: likely to be beneficial (effectiveness 75%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1316

#### **Present food frozen in ice**

Two studies in the USA and Ireland found that when frozen food was presented, feeding time increased and inactivity decreased. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1321

#### **Present food items whole instead of processed**

One before-and-after study in the USA found that when food items were presented whole instead of chopped, the amount of food consumed and feeding time increased in macaques. *Assessment: likely to be beneficial (effectiveness 80%; certainty 50%; harms 0%).*

### **Present feeds at different crowd levels**

One before-and-after study in the USA found that when smaller crowds were present foraging and object use in chimpanzees increased. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1324

## **Maximise both vertical and horizontal presentation locations**

One controlled study in the UK and Madagascar found that less time was spent feeding on provisioned food in the indoor enclosure when food was hung in trees in an outdoor enclosure. One replicated, before-and-after study in the UK reported that when vertical and horizontal food locations were increased feeding time increased. *Assessment: likely to be beneficial (effectiveness 65%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1328

#### **Trade-off between benefit and harms**

#### **Present food in puzzle feeders**

Three studies including two before-and-after studies in the USA and UK found that presenting food in puzzle feeders, increased foraging behaviour, time spent feeding and tool use but also aggression. *Assessment: trade-offs between benefits and harms (effectiveness 55%; certainty 80%; harms 60%).*

https://www.conservationevidence.com/actions/1318

#### **Unknown effectiveness (limited evidence)**

#### **Present food in water (including dishes and ponds)**

One replicated, before-and-after study in the USA found that when exposed to water filled troughs, rhesus monkeys were more active and increased their use of tools. *Assessment: unknown effectiveness (effectiveness 60%; certainty 30%; harms 0%).*

#### **Present food dipped in food colouring**

One before-and-after study in the USA found that when food was presented after being dipped in food colouring, orangutans ate more and spent less time feeding. *Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 20%).*

https://www.conservationevidence.com/actions/1322

## **Provide live vegetation in planters for foraging**

One replicated, before-and-after study in the USA reported that chimpanzees spent more time foraging when provided with planted rye grass and scattered sunflower seeds compared to browse and grass added to the enclosure with their normal diet. *Assessment: unknown effectiveness (effectiveness 80%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1327

#### **No evidence found (no assessment)**


## 9.3.2 Diet manipulation


## **Likely to be beneficial**

## **Formulate diet to reflect nutritional composition of wild foods (including removal of domestic fruits)**

Two replicated, before-and-after studies in the USA and UK found that when changing the diet of captive primates to reflect nutritional compositions of wild foods, there was a decrease in regurgitation and reingestion, aggression and self-directed behaviours. *Assessment: likely to be beneficial (effectiveness 70%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1329

#### **Provide cut branches (browse)**

One replicated, before-and-after study in the Netherlands and Germany found that captive gorillas when presented with stinging nettles use the same processing skills as wild gorillas to forage. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

#### **Provide live invertebrates**

One before-and-after study in the UK found that providing live invertebrates to captive lorises increased foraging levels and reduced inactivity. *Assessment: likely to be beneficial (effectiveness 85%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1333

### **Provide fresh produce**

One replicated, before-and-after study in the USA found that when fresh produce was offered feeding time increased and inactivity decreased in rhesus macaques. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 1%).*

https://www.conservationevidence.com/actions/1335

#### **No evidence found (no assessment)**


# 9.3.3 Feeding Schedule


## **Likely to be beneficial**

## **Change feeding times**

One controlled study in the USA found that changing feeding times decreased inactivity and abnormal behaviours in chimpanzees. *Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1338

### **Trade-off between benefit and harms**

### **Change the number of feeds per day**

Two before-and-after studies in Japan and the USA found that changing the number of feeds per day increased time spent feeding in chimpanzees but also increased hair eating in baboons. *Assessment: trade-offs between benefits and harms (effectiveness 70%; certainty 50%; harms 50%).*

https://www.conservationevidence.com/actions/1337

#### **No evidence found (no assessment)**


# 9.3.4 Social group manipulation


## **Trade-off between benefit and harms**

## **Feed individuals in social groups**

One replicated, controlled study in the USA found that an enrichment task took less time to complete when monkeys were in social groups than when feeding alone. One before-and-after study in Italy found that in the presence of their groupmates monkeys ate more unfamiliar foods during the first encounter. *Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 50%; harms 25%).*

https://www.conservationevidence.com/actions/1343

## **No evidence found (no assessment)**


# 10. SOME ASPECTS OF CONTROL OF FRESHWATER INVASIVE SPECIES

#### **David Aldridge, Nancy Ockendon, Ricardo Rocha, Rebecca K. Smith & William J. Sutherland**

#### **Expert assessors**

**David Aldridge**, University of Cambridge, UK **Olaf Booy**, Animal and Plant Health Agency, UK **Manuel A. Duenas**, Centre for Ecology & Hydrology, UK **Alison Dunn**, University of Leeds, UK **Robert Francis**, King's College London, UK **Belinda Gallardo**, Pyrenean Institute of Ecology, Spain **Nancy Ockendon**, University of Cambridge, UK **Trevor Renals**, Environment Agency, UK **Emmanuelle Sarat**, International Union for Conservation of Nature, France **Sonal Varia**, The Centre for Agriculture and Bioscience International, UK **Alexandra Zieritz**, University of Nottingham, UK **Ana L. Nunes**, The Centre for Agriculture and Bioscience International, UK **Deborah Hofstra**, National Institute of Water and Atmospheric Research, New Zealand **Jonathan Newman**, Waterland Management Ltd, UK **Johan van Valkenburg**, National Plant Protection Organization, The Netherlands **Ryan Wersal**, Lonza Water Care, Alpharetta, Georgia, US **Ricardo Rocha**, University of Cambridge, UK

**Scope of assessment**: for the control of 12 invasive freshwater species.

**Assessed:** American bullfrog and *Procambarus* spp. crayfish 2015; parrot's feather 2017; all other species 2016.

**Effectiveness measure** is the median % score for effectiveness.

**Certainty measure** is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects to non-target native species. This was not assessed for some species in this chapter.

*Potential impacts on non-target species should be considered carefully before implementing any control action.*

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

## 10.1.1 Parrot's feather *Myriophyllum aquaticum*



## **Beneficial**

## **Chemical control using the herbicide 2,4-D**

Five laboratory studies (three replicated, controlled and two randomized, controlled) in the USA and Brazil and two replicated, randomized, field studies in Portugal reported that treatment with 2,4-D reduced growth, biomass or cover of parrot's feather. *Assessment: beneficial (effectiveness 80%; certainty 80%; harms 0%).*

https://www.conservationevidence.com/actions/1606

## **Likely to be beneficial**

## **Chemical control using the herbicide carfentrazone-ethyl**

Five laboratory studies (one replicated, controlled, before-and-after, three replicated, controlled and one randomized, controlled) in the USA reported that treatment with carfentrazone-ethyl reduced growth. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 5%).*

https://www.conservationevidence.com/actions/1676

## **Chemical control using the herbicide triclopyr**

Three replicated, controlled laboratory studies in the USA and New Zealand reported that treatment with triclopyr reduced growth or that cover was lower than that of plants treated with glyphosate. One replicated, controlled field study and one replicated, before-and-after field study in New Zealand reported that cover was reduced after treatment with triclopyr but one of these studies reported that cover later increased to near pre-treatment levels. *Assessment: likely to be beneficial (effectiveness 60%; certainty 55%; harms 0%).*

## **Chemical control using the herbicide diquat**

Two replicated, controlled laboratory studies in the USA reported reduced growth after exposure to diquat. However, one replicated, randomized, controlled field study in Portugal reported no reduction in biomass following treatment with diquat. *Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1680

## **Chemical control using the herbicide endohall**

Two replicated, controlled laboratory studies in the USA and New Zealand reported a reduction in biomass after treatment with endothall. However, one replicated, controlled field study in New Zealand found that cover declined after treatment with endothall but later cover increased close to pre-treatment levels. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1681

#### **Chemical control using other herbicides**

One replicated, randomized, controlled field study in Portugal and one replicated, controlled, laboratory study in the USA reported reduced growth or vegetation cover after treatment with glyphosate. Two replicated, randomized, controlled laboratory studies (one of which was randomized) in the USA have found that the herbicide imazapyr reduced growth. Four replicated, controlled (one of which was randomized) laboratory studies in the USA and New Zealand reported reduced growth after treatment with the herbicides imazamox, flumioxazin, dichlobenil and florpyrauxifen-benzyl. Two replicated, controlled (one of which was randomized) field studies in Portugal and New Zealand reported a decrease in cover after treatment with dichlobenil followed by recovery. One replicated, randomized, controlled field study in Portugal reported reduced biomass after treatment with gluphosinate-ammonium. Three replicated, controlled laboratory studies in New Zealand and the USA found no reduction in growth after treatment with clopyralid, copper chelate or fluridone. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

*Some Aspects of Control of Freshwater Invasive Species*

## **Reduction of trade through legislation and codes of conduct**

One randomized, before-and-after trial in the Netherlands reported that the implementation of a code of conduct reduced the trade of invasive aquatic plants banned from sale. One study in the USA found that despite a state-wide trade ban on parrot's feather plants, these could still be purchased in some stores. *Assessment: likely to be beneficial (effectiveness 60%; certainty 45%; harms 0%).*

https://www.conservationevidence.com/actions/1604

#### **Trade-off between benefit and harms**

#### **Biological control using herbivores**

Two replicated, randomized studies in Argentina and the USA found that stocking with grass carp reduced the biomass or abundance of parrot's feather. However, one controlled laboratory study in Portugal found that grass carp did not reduce biomass or cover of parrot's feather. One field study in South Africa found that one *Lysathia* beetle species retarded the growth of parrot's feather. *Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 40%; harms 20%).*

https://www.conservationevidence.com/actions/1599

#### **Unknown effectiveness (limited evidence)**

#### **Water level drawdown**

One replicated, randomized, controlled laboratory study in the USA found that water removal to expose plants to drying during the summer led to lower survival of parrot's feather plants than water removal during winter. *Assessment: unknown effectiveness (effectiveness 60%; certainty 30%; harms 0%).*

## **Biological control using plant pathogens**

One study in South Africa found that exposure to a strain of the bacterium *Xanthomonas campestris* did not affect the survival of parrot's feather. *Assessment: unknown effectiveness (effectiveness 5%; certainty 10%; harms 0%).*

https://www.conservationevidence.com/actions/1601

#### **No evidence found (no assessment)**


# 10.1.2 Floating pennywort *Hydrocotyle ranunculoides*


## **Beneficial**

## **Chemical control using herbicides**

A controlled, replicated field study in the UK found that the herbicide 2,4-D amine achieved almost 100% mortality of floating pennywort, compared with the herbicide glyphosate (applied without an adjuvant) which achieved negligible mortality. *Assessment: beneficial (effectiveness 80%; certainty 70%).*

https://www.conservationevidence.com/actions/1127

#### **Likely to be beneficial**

#### **Flame treatment**

A controlled, replicated study in the Netherlands found that floating pennywort plants were killed by a three second flame treatment with a three second repeat treatment 11 days later. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%).*

https://www.conservationevidence.com/actions/1131

## **Physical removal**

Two studies, one in Western Australia and one in the UK, found physical removal did not completely eradicate floating pennywort. *Assessment: likely to be beneficial (effectiveness 40%; certainty 40%).*

https://www.conservationevidence.com/actions/1126

**Unknown effectiveness (limited evidence)**

## **Combination treatment using herbicides and physical removal**

A before-and-after study in Western Australia found that a combination of cutting followed by a glyphosate chemical treatment, removed floating pennywort. *Assessment: unknown effectiveness (effectiveness 70%; certainty 35%).*

https://www.conservationevidence.com/actions/1128

### **Unlikely to be beneficial**

### **Biological control using co-evolved, host-specific herbivores**

A replicated laboratory and field study in South America found that the South American weevil fed on water pennywort but did not reduce the biomass. *Assessment: unlikely to be beneficial (effectiveness 20%; certainty 50%).*

https://www.conservationevidence.com/actions/1123

### **Use of hydrogen peroxide**

A controlled, replicated study in the Netherlands found that hydrogen peroxide sprayed on potted floating pennywort plants at 30% concentration resulted in curling and transparency of the leaves but did not kill the plants. *Assessment: unlikely to be beneficial (effectiveness 10%; certainty 60%).*

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 10.1.3 Water primrose *Ludwigia spp.*

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for controlling water primrose? Likely to be beneficial** ● Biological control using co-evolved, host specific herbivores ● Chemical control using herbicides ● Combination treatment using herbicides and physical removal **Unlikely to be beneficial** ● Physical removal **No evidence found (no assessment)** ● Biological control using fungal-based herbicides ● Biological control using native herbivores ● Environmental control (e.g. shading, altered flow, altered rooting depth, or dredging) ● Excavation of banks ● Public education ● Use of a tarpaulin ● Use of flame treatment ● Use of hydrogen peroxide ● Use of liquid nitrogen ● Use of mats placed on the bottom of the water body

## **Likely to be beneficial**

#### **Biological control using co-evolved, host specific herbivores**

A controlled, replicated study in China, found a flea beetle caused heavy feeding destruction to the prostrate water primrose. A before-and-after study in the USA found that the introduction of flea beetles to a pond significantly reduced the abundance of large-flower primrose-willow. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%).*

https://www.conservationevidence.com/actions/1135

#### **Chemical control using herbicides**

A controlled, replicated laboratory study in the USA found that the herbicide triclopyr TEA applied at concentrations of 0.25% killed 100% of young cultivated water primrose within two months. A before-and-after field study in the UK found that the herbicide glyphosate caused 97% mortality when mixed with a non-oil based sticking agent and 100% mortality when combined with TopFilm. A controlled, replicated, randomized study in Venezuela, found that use of the herbicide halosulfuron-methyl (Sempra) resulted in a significant reduction in water primrose coverage without apparent toxicity to rice plants. *Assessment: likely to be beneficial (effectiveness 80%; certainty 60%).*

https://www.conservationevidence.com/actions/1139

#### **Combination treatment using herbicides and physical removal**

A study in the USA found that application of glyphosate and a surface active agent called Cygnet-Plus followed by removal by mechanical means killed 75% of a long-standing population of water primrose. A study in Australia found that a combination of herbicide application, physical removal, and other actions such as promotion of native plants and mulching reduced the cover of Peruvian primrose-willow by 85–90%. *Assessment: likely to be beneficial (effectiveness 70%; certainty 55%).*

## **Unlikely to be beneficial**

## **Physical removal**

A study in the USA found that hand pulling and raking water primrose failed to reduce its abundance at one site, whereas hand-pulling from the margins of a pond eradicated a smaller population of water primrose at a second site. *Assessment: unlikely to be beneficial (effectiveness 30%; certainty 50%).*

https://www.conservationevidence.com/actions/1138

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 10.1.4 Skunk cabbage *Lysichiton americanus*

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for controlling skunk cabbage?**



## **Likely to be beneficial**

## **Chemical control using herbicides**

Two studies in the UK found that application of the chemical 2,4-D amine appeared to be successful in eradicating skunk cabbage stands. One of these studies also found glyphosate eradicated skunk cabbage. However, a study in the UK found that glyphosate did not eradicate skunk cabbage, but resulted in only limited reduced growth of plants. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%).*

https://www.conservationevidence.com/actions/1102

### **Physical removal**

Two studies in Switzerland and the Netherlands, reported effective removal of recently established skunk cabbage plants using physical removal, one reporting removal of the entire stock within five years. A third study in Germany reported that after four years of a twice yearly full removal programme, a large number of plants still needed to be removed each year. *Assessment: likely to be beneficial (effectiveness 65%; certainty 55%).*

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 10.1.5 New Zealand pigmyweed *Crassula helmsii*

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for controlling** *Crassula helmsii***?**



#### **Beneficial**

### **Chemical control using herbicides**

Seven studies in the UK, including one replicated, controlled study, found that applying glyphosate reduced *Crassula helmsii*. Three out of four studies in the UK, including one controlled study, found that applying diquat or diquat alginate reduced or eradicated *C. helmsii*. One small trial found no effect of diquat on *C. helmsii* cover. One replicated, controlled study in the UK found dichlobenil reduced biomass of submerged *C. helmsii* but one small before-and-after study found no effect of dichlobenil on *C. helmsii*. A replicated, controlled study found that treatment with terbutryne partially reduced biomass of submerged *C. helmsii* and that asulam, 2,4-D amine and dalapon reduced emergent *C. helmsii*. *Assessment: beneficial (effectiveness 78%; certainty 75%).*

https://www.conservationevidence.com/actions/1279

#### **Decontamination to prevent further spread**

One controlled, replicated container trial in the UK found that submerging *Crassula helmsii* fragments in hot water led to higher mortality than drying out plants or a control. *Assessment: beneficial (effectiveness 80%; certainty 70%).*

### **Likely to be beneficial**

#### **Use lightproof barriers to control plants**

Five before-and-after studies in the UK found that covering with black sheeting or carpet eradicated or severely reduced cover of *Crassula helmsii*. *Assessment: likely to be beneficial (effectiveness 65%; certainty 50%).*

https://www.conservationevidence.com/actions/1294

#### **Use salt water to kill plants**

Two replicated, controlled container trials and two before-and-after field trials in the UK found that seawater eradicated *Crassula helmsii*. *Assessment: likely to be beneficial (effectiveness 80%; certainty 45%).*

https://www.conservationevidence.com/actions/1288

#### **Unknown effectiveness (limited evidence)**

#### **Use a combination of control methods**

One before-and-after study in the UK found that covering *Crassula helmsii* with carpet followed by treatment with glyphosate killed 80% of the plant. *Assessment: unknown effectiveness (effectiveness 75%; certainty 30%).*

https://www.conservationevidence.com/actions/1313

#### **Unlikely to be beneficial**

#### **Use dyes to reduce light levels**

One replicated, controlled study in the UK found that applying aquatic dye, along with other treatments, did not reduce cover of *Crassula helmsii*. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 53%).*

https://www.conservationevidence.com/actions/1293

### **Use grazing to control plants**

One of two replicated, controlled studies in the UK found that excluding grazing reduce abundance and coverage of *Crassula helmsii*. The other study found that ungrazed areas had higher coverage of *C. helmsii* than grazed plots. *Assessment: unlikely to be beneficial (effectiveness 23%; certainty 43%).*

## **Use hot foam to control plants**

One replicated, controlled study in the UK found that treatment with hot foam, along with other treatments, did not control *Crassula helmsii*. A beforeand-after study in the UK found that treatment with hot foam partially destroyed *C. helmsii*. *Assessment: unlikely to be beneficial (effectiveness 20%; certainty 50%).*

https://www.conservationevidence.com/actions/1286

### **Use hydrogen peroxide to control plants**

One controlled tank trial in the UK found that hydrogen peroxide did not control *Crassula helmsii*. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 50%).*

https://www.conservationevidence.com/actions/1281

#### **No evidence found (no assessment)**


# 10.2 Threat: Invasive molluscs

## 10.2.1 Asian clams

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for controlling Asian clams?**


#### **Beneficial**

## **Add chemicals to the water**

Two replicated laboratory studies and one controlled, replicated field study found that chlorine, potassium and copper killed Asian clams. Increasing chemical concentration and water temperature killed more clams in less time. One controlled field trial achieved 80% and 100% mortality of Asian clams using encapsulated control agents (SB1000 and SB2000 respectively) in irrigation systems. *Assessment: beneficial (effectiveness 75%; certainty 70%).*

https://www.conservationevidence.com/actions/1118

## **Change salinity of water**

A controlled, replicated laboratory study from the USA found that exposure to saline water killed all Asian clams. *Assessment: beneficial (effectiveness 65%; certainty 68%).*

https://www.conservationevidence.com/actions/1115

## **Mechanical removal**

A controlled before-and-after study from North America found suction dredging of sediment reduced an Asian clam population by 96%, and these effects persisted for a year. A replicated, controlled, before-and-after field trial in Ireland showed that three types of dredges were effective at removing between 74% and >95% of the Asian clam biomass. *Assessment: beneficial (effectiveness 80%; certainty 78%).*

https://www.conservationevidence.com/actions/1120

#### **Likely to be beneficial**

#### **Change temperature of water**

A controlled laboratory study from the USA found that exposure to water at temperatures of 37°C and 36°C killed all Asian clams within 2 and 4 days, respectively. *Assessment: likely to be beneficial (effectiveness 60%; certainty 55%).*

https://www.conservationevidence.com/actions/1116

## **Clean equipment**

A field study from Portugal found that mechanical removal, followed by regular cleaning and maintenance of industrial pipes at a power plant permanently removed an Asian clam population. A field study from Portugal found that adding a sand filter to a water treatment plant reduced an Asian clam population. *Assessment: likely to be beneficial (effectiveness 75%; certainty 50%).*

*Some Aspects of Control of Freshwater Invasive Species*

## **Use of gas-impermeable barriers**

One controlled study from North America found that placing gas impermeable fabric barriers on a lake bottom (several small and one large area) reduced populations of Asian clams. *Assessment: likely to be beneficial (effectiveness 78%; certainty 60%).*

https://www.conservationevidence.com/actions/1117

## **Unlikely to be beneficial**

#### **Reduce oxygen in water**

A controlled laboratory study from the USA found that Asian clams were not susceptible to low oxygen levels in the water. *Assessment: unlikely to be beneficial (effectiveness 10%; certainty 50%).*

https://www.conservationevidence.com/actions/1113

#### **No evidence found (no assessment)**


# 10.3.1 Ponto-Caspian gammarids


● Exchange ballast water

● Exposure to disease-causing organisms

## **Likely to be beneficial**

## **Change salinity of the water**

One of two replicated studies, including one controlled study, in Canada and the UK found that increasing the salinity level of water killed the majority of invasive shrimp within five hours. One found that increased salinity did not kill invasive killer shrimp. *Assessment: likely to be beneficial (effectiveness 40%; certainty 50%).*

#### **Change water temperature**

A controlled laboratory study from the UK found that heating water in excess of 40°C killed invasive killer shrimps. *Assessment: likely to be beneficial (effectiveness 80%; certainty 50%).*

https://www.conservationevidence.com/actions/1092

## **Dewatering (drying out) habitat**

A replicated, controlled laboratory study from Poland found that lowering water levels in sand (dewatering) killed three species of invasive freshwater shrimp, although one species required water content levels of 4% and below before it was killed. *Assessment: likely to be beneficial (effectiveness 60%; certainty 50%).*

https://www.conservationevidence.com/actions/1094

#### **Exposure to parasites**

A replicated, controlled experimental study in Canada found that a parasitic mould reduced populations of freshwater invasive shrimp. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%).*

https://www.conservationevidence.com/actions/1089

#### **Unlikely to be beneficial**

#### **Add chemicals to water**

A controlled laboratory study from the UK found that four of nine substances added to freshwater killed invasive killer shrimp, but were impractical (iodine solution, acetic acid, Virkon S and sodium hypochlorite). Five substances did not kill invasive killer shrimp (methanol, citric acid, urea, hydrogen peroxide and sucrose). *Assessment: unlikely to be beneficial (effectiveness 35%; certainty 60%).*

https://www.conservationevidence.com/actions/1095

## **Change water pH**

A controlled laboratory study from the UK found that lowering the pH of water did not kill invasive killer shrimp. *Assessment: unlikely to be beneficial (effectiveness 0%; certainty 50%).*

## **Control movement of gammarids**

Two replicated studies, including one controlled study, in the USA and UK found that movements of invasive freshwater shrimp slowed down or were stopped when shrimp were placed in water that had been exposed to predatory fish or was carbonated. *Assessment: likely to be beneficial (effectiveness 20%; certainty 40%).*

https://www.conservationevidence.com/actions/1088

#### **No evidence found (no assessment)**

We have captured no evidence for the following interventions:


## 10.3.2 *Procambarus* spp. crayfish


## **Likely to be beneficial**

## **Add chemicals to the water**

One replicated study in Italy found that natural pyrethrum at concentrations of 0.05 mg/l and above was effective at killing red swamp crayfish both in the laboratory and in a river, but not in drained burrows. *Assessment: likely to be beneficial (effectiveness 80%; certainty 50%; harms 0%).*

https://www.conservationevidence.com/actions/1036

## **Sterilization of males**

One replicated laboratory study from Italy found that exposing male red swamp crayfish to X-rays reduced the number of offspring they produced. *Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).*

https://www.conservationevidence.com/actions/1032

## **Trapping and removal**

One controlled, replicated study from Italy found that food (tinned meat) was a more effective bait in trapping red swamp crayfish, than using pheromone treatments or no bait (control). Baiting with food increased trapping success compared to trapping without bait. *Assessment: likely to be beneficial (effectiveness 40%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1029

### **Trapping combined with encouragement of predators**

One before-and-after study in Switzerland and a replicated, paired site study from Italy found that a combination of trapping and predation was more effective at reducing red swamp crayfish populations than predation alone. *Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 0%).*

## **Unknown effectiveness (limited evidence)**

## **Create barriers**

One before-and-after study from Italy found that the use of concrete dams across a stream was effective at containing spread of the population upstream. *Assessment: unknown effectiveness (effectiveness 30%; certainty 30%; harms 0%).*

https://www.conservationevidence.com/actions/1037

## **Unlikely to be beneficial**

## **Encouraging predators**

Two replicated, controlled studies in Italy found that eels fed on the red swamp crayfish and reduced population size. One replicated, controlled study found that pike predated red swamp crayfish. *Assessment: unlikely to be beneficial (effectiveness 30%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1030

#### **No evidence found (no assessment)**


# 10.4 Threat: Invasive fish

# 10.4.1 Brown and black bullheads


## **Beneficial**

## **Application of a biocide**

Two studies in the UK and USA found that rotenone successfully eradicated black bullhead. *Assessment: beneficial (effectiveness 80%; certainty 80%).*

https://www.conservationevidence.com/actions/1050

## **Likely to be beneficial**

## **Netting**

A replicated study in a nature reserve in Belgium found that double fyke nets could be used to significantly reduce the population of large brown bullheads. *Assessment: likely to be beneficial (effectiveness 55%; certainty 55%).*

https://www.conservationevidence.com/actions/1051

#### **No evidence found (no assessment)**


# 10.4.2 Ponto-Caspian gobies


## **Beneficial**

## **Changing salinity**

A replicated controlled laboratory study in Canada found 100% mortality of round gobies within 48 hours of exposure to water of 30% salinity. *Assessment: beneficial (effectiveness 90%; certainty 75%).*

## **Likely to be beneficial**

## **Use of barriers to prevent migration**

A controlled, replicated field study in the USA found that an electrical barrier prevented movement of round gobies across it, and that increasing electrical pulse duration and voltage increased the effectiveness of the barrier. *Assessment: likely to be beneficial (effectiveness 50%; certainty 45%).*

https://www.conservationevidence.com/actions/1074

#### **No evidence found (no assessment)**


# 10.5 Threat: Invasive reptiles

## 10.5.1 Red-eared terrapin *Trachemys scripta*

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions for controlling red-eared terrapin?**


#### **Likely to be beneficial**

#### **Direct removal of adults**

Two studies, a replicated study from Spain using Aranzadi turtle traps, and an un-replicated study in the British Virgin Islands using sein netting, successfully captured but did not eradicate red-eared terrapin populations. *Assessment: likely to be beneficial (effectiveness 40%; certainty 50%).*

## **Unlikely to be beneficial**

## **Application of a biocide**

A replicated, controlled laboratory study in the USA, found that application of glyphosate to the eggs of red-eared terrapins reduced hatching success to 73% but only at the highest experimental concentration of glyphosate and a surface active agent. *Assessment: unlikely to be beneficial (effectiveness 15%; certainty 50%).*

https://www.conservationevidence.com/actions/1059

### **No evidence found (no assessment)**


## 10.6.1 American bullfrog *Lithobates catesbeiana*


## **Likely to be beneficial**

## **Biological control using native predators**

One replicated, controlled study conducted in northeast Belgium found the introduction of the northern pike led to a strong decline in bullfrog tadpole numbers. *Assessment: likely to be beneficial (effectiveness 70%; certainty 40%; harms 0%).*

## **Direct removal of adults**

One replicated study in Belgium found catchability of adult bullfrogs in small shallow ponds using a double fyke net to be very low. One small study in the USA found that adult bullfrogs can be captured overnight in a single trap floating on the water surface. One replicated, controlled study in the USA found that bullfrog populations rapidly rebounded following intensive removal of the adults. One study in France found a significant reduction in the number of recorded adults and juveniles following the shooting of metamorphosed individuals before reproduction, when carried out as part of a combination treatment. *Assessment: likely to be beneficial (effectiveness 50%; certainty 70%; harms 0%).*

https://www.conservationevidence.com/actions/1045

### **Direct removal of juveniles**

One replicated study in Belgium found double fyke nets were effective in catching bullfrog tadpoles in small shallow ponds. One study in France found a significant reduction in the number of recorded adults and juveniles following the removal of juveniles by trapping, when carried out as part of a combination treatment. *Assessment: likely to be beneficial (effectiveness 70%; certainty 60%; harms 0%).*

https://www.conservationevidence.com/actions/1046

#### **Unknown effectiveness (limited evidence)**

### **Application of a biocide**

One replicated, controlled study in the USA reported a number of chemicals killed American bullfrogs, including caffeine (10% solution), chloroxylenol (5% solution), and a combined treatment of Permethrin (4.6% solution) and Rotenone (1% solution). *Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).*

#### **No evidence found (no assessment)**


# 11. SOME ASPECTS OF ENHANCING NATURAL PEST CONTROL

#### **Hugh L. Wright, Joscelyne E. Ashpole, Lynn V. Dicks, James Hutchison, Caitlin G. McCormack & William J. Sutherland**

#### **Expert assessors**

**Barbara Smith**, Game and Wildlife Conservation Trust, UK **Tony Harding**, Rothamsted Research, UK **Anthony Goggin**, Linking Environment and Farming (LEAF), UK **Felix Wackers**, BioBest/University of Lancaster, Belgium/UK **Melvyn Fidgett**, Syngenta, UK **Michael Garratt**, University of Reading, UK **Michelle Fountain**, East Malling Research, UK **Phillip Effingham**, Greentech Consultants, UK **Stephanie Williamson**, Pesticides Action Network, UK **Toby Bruce**, Rothamsted Research, UK **Andrew Wilby**, University of Lancaster, UK **Eve Veromann**, Estonian University of Life Sciences, Estonia **Mattias Jonsson**, Swedish University of Agricultural Sciences, Sweden **Vicky Kindemba**, Buglife, UK **Steve Sait**, University of Leeds, UK

**Scope of assessment**: 22 of 92 possible actions to enhance natural regulation of pests (including animals, plants, fungi, bacteria and viruses) in agricultural systems across the world.

#### **Assessed:** 2014.

**Effectiveness measure** is the median % score.

**Certainty measure** is the median % certainty of evidence, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects for the farmer such as reduced yield and profits or increased costs.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 11.1 Reducing agricultural pollution

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions that reduce agricultural pollution for enhancing natural pest regulation?**


#### **Unknown effectiveness (limited evidence)**

#### **Alter the timing of insecticide use**


## **Delay herbicide use**


#### **Incorporate parasitism rates when setting thresholds for insecticide use**


http://www.conservationevidence.com/actions/726

#### **Use pesticides only when pests or crop damage reach threshold levels**


#### **Evidence not assessed**

#### **Convert to organic farming**


# 11.2 All farming systems

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on all farming systems for enhancing natural pest regulation?**


## **Likely to be beneficial**

## **Grow non-crop plants that produce chemicals that attract natural enemies**

• *Natural enemies:* Four studies from China, Germany, India and Kenya tested the effects of growing plants that produce chemicals that attract natural enemies. Three (including one replicated, randomized, controlled trail) found higher numbers of natural enemies in plots with plants that produce attractive chemicals, and one also found that the plant used attracted natural enemies in lab studies. One found no effect on parasitism but the plant used was found not to be attractive to natural enemies in lab studies.


#### **Use chemicals to attract natural enemies**


## **Trade-off between benefit and harms**

#### **Leave part of the crop or pasture unharvested or uncut**


## **Unknown effectiveness (limited evidence)**

## **Plant new hedges**


http://www.conservationevidence.com/actions/752

### **Use alley cropping**


one study found effects varied with pest group and between years. One study found more pest damage to crops but another study found no effect.


http://www.conservationevidence.com/actions/718

#### **Evidence not assessed**

## **Use mass-emergence devices to increase natural enemy populations**


# 11.3 Arable farming

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on arable farming systems for enhancing natural pest regulation?**


#### **Beneficial**

#### **Combine trap and repellent crops in a push-pull system**


found no effect on pest infestation, but pests were scarce throughout. Two replicated, controlled studies (one also randomized) found fewer witchweeds.


#### **Trade-off between benefit and harms**

#### **Use crop rotation in potato farming systems**


#### **Unlikely to be beneficial**

#### **Create beetle banks**


#### **Likely to be ineffective or harmful**

### **Incorporate plant remains into the soil that produce weedcontrolling chemicals**


# 11.4 Perennial farming

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on perennial farming systems for enhancing natural pest regulation?**


## **Likely to be beneficial**

#### **Exclude ants that protect pests**


#### **Unknown effectiveness (limited evidence)**

### **Allow natural regeneration of ground cover beneath perennial crops**


covers. Two studies found fewer pests, whilst two studies found effects on pests and crop damage varied for different pest or disease groups. One study found more pests in natural than in sown ground covers.


http://www.conservationevidence.com/actions/720

	- *Natural enemies:* One replicated, controlled study from Australia found predatory ants occupied more cashew trees when colonies were kept isolated.
	- *Pest damage and yield:* The same study found lower pest damage to cashews and higher yields.
	- *The crop studied* was cashew.
	- *Assessment: unknown effectiveness (effectiveness 60%; certainty 19%; harms 0%).*

# 11.5 Livestock farming and pasture



## **Likely to be beneficial**

### **Grow plants that compete with damaging weeds**


#### **Unknown effectiveness (limited evidence)**

## **Delay mowing or first grazing date on pasture or grassland**


#### **Likely to be ineffective or harmful**

### **Use grazing instead of cutting for pasture or grassland management**


http://www.conservationevidence.com/actions/885

#### **Use mixed pasture**

• W*eeds:* Two of two studies (randomized and replicated and one also controlled) from the USA found weeds were negatively affected by mixed compared to monoculture pasture.


# 12. ENHANCING SOIL FERTILITY

**Georgina Key, Mike Whitfield, Lynn V. Dicks, William J. Sutherland & Richard D. Bardgett**

#### **Expert assessors**

**Martin Collison**, Collison and Associates Limited, UK **Julia Cooper**, Newcastle University, UK **Thanasis Dedousis**, PepsiCo Europe **Richard Heathcote**, Heineken, S&N UK Ltd **Shamal Mohammed**, Agriculture and Horticulture Development Board, Cranfield University, UK **Andrew Molyneux**, Huntapac Produce Ltd, UK **Wim van der Putten**, Netherlands Institute of Ecology **Brendan Roth**, Department for Environment, Food & Rural Affairs, UK **Franciska de Vries**, University of Manchester, UK

**Scope of assessment**: actions to enhance soil fertility for agricultural systems across the world.

**Assessed:** 2014.

**Effectiveness measure** is the median % score.

**Certainty measure** is the median % certainty of evidence, determined by the quantity and quality of the evidence in the synopsis.

**Harm measure** is the median % score for negative side-effects for the farmer such as reduced yield, crop quality or profits, or increased costs. This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

#### Full details of the evidence are available at **www.conservationevidence.com**

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

# 12.1 Reducing agricultural pollution


#### **Unknown effectiveness (limited evidence)**

### **Change the timing of manure application**


## **Likely to be ineffective or harmful**

## **Reduce fertilizer, pesticide or herbicide use generally**


# 12.2 All farming systems

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on all farming systems for enhancing soil fertility?**


## **Likely to be beneficial**

### **Control traffic and traffic timing**


#### *Enhancing Soil Fertility*


http://www.conservationevidence.com/actions/899

## **Trade-off between benefit and harms**

## **Change tillage practices**


erosion. Seven trials (one also controlled and randomized) showed reduced soil loss and runoff under reduced tillage compared to conventional ploughing. One trial showed no differences between tillage systems, but demonstrated that across-slope cultivation reduced soil loss compared to up-and-downslope cultivation. Two trials, showed that no-tillage increased soil loss in the absence of crop cover.


## **Convert to organic farming**


http://www.conservationevidence.com/actions/895

## **Plant new hedges**


• *Assessment: trade-offs between benefit and harms (effectiveness 49%; certainty 45%; harms 20%).*

http://www.conservationevidence.com/actions/744

#### **Unknown effectiveness (limited evidence)**

#### **Change the timing of ploughing**


# 12.3 Arable farming

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on arable farming systems for enhancing soil fertility?**


## **Beneficial**

## **Amend the soil using a mix of organic and inorganic amendments**


http://www.conservationevidence.com/actions/902

#### **Grow cover crops when the field is empty**

• *Biodiversity*: One controlled, randomized, replicated experiment in Martinique found that growing cover crops resulted in more diverse nematode communities. One replicated trial from the USA found greater microbial biomass under ryegrass compared to a ryegrass/ vetch cover crop mix.


http://www.conservationevidence.com/actions/898

#### **Use crop rotation**


## **Likely to be beneficial**

## **Amend the soil with formulated chemical compounds**


#### *Enhancing Soil Fertility*


http://www.conservationevidence.com/actions/909

## **Grow cover crops beneath the main crop (living mulches) or between crop rows**


http://www.conservationevidence.com/actions/897

### **Trade-off between benefit and harms**

### **Add mulch to crops**

• *Biodiversity*: Three replicated trials from Canada, Poland and Spain (including one also controlled, one also randomised and one also controlled and randomised) showed that adding mulch to crops (whether shredded paper, municipal compost or straw) increased soil animal and fungal numbers, diversity and activity. Of these, one trial also showed that mulch improved soil structure and increased soil organic matter.


### **Amend the soil with fresh plant material or crop remains**


#### *Enhancing Soil Fertility*


http://www.conservationevidence.com/actions/910

### **Amend the soil with manures and agricultural composts**


and a positive effect on soil physical properties when manure and compost were applied. One study from Germany found no effect of manure on organic matter levels.


http://www.conservationevidence.com/actions/911

#### **Amend the soil with municipal wastes or their composts**


http://www.conservationevidence.com/actions/890

#### **Incorporate leys into crop rotation**


## **Retain crop residues**


http://www.conservationevidence.com/actions/907

#### **Unknown effectiveness (limited evidence)**

## **Amend the soil with bacteria or fungi**


## **Amend the soil with composts not otherwise specified**


http://www.conservationevidence.com/actions/889

#### **Amend the soil with crops grown as green manures**


http://www.conservationevidence.com/actions/908

### **Amend the soil with non-chemical minerals and mineral wastes**


http://www.conservationevidence.com/actions/892

## **Amend the soil with organic processing wastes or their composts**

• *Nutrient loss*: Two controlled, replicated trials from Spain and the UK (one also randomized) measured the effect of adding composts to soil. One trial found applying high rates of cotton gin compost and poultry manure improved soil structure and reduced soil loss, but increased nutrient loss. One trial found improved nutrient retention and increased barley *Hordeum vulgare* yield when molasses were added.


http://www.conservationevidence.com/actions/891

#### **Encourage foraging waterfowl**


http://www.conservationevidence.com/actions/711


# 12.4 Livestock and pasture farming

**Based on the collated evidence, what is the current assessment of the effectiveness of interventions on livestock and pasture farming systems for enhancing soil fertility?**


## **Likely to be beneficial**

## **Reduce grazing intensity**


## **Trade-off between benefit and harms**

 **Restore or create low input grasslands**


# This book need not end here...

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*Edited by Bhaskar Vira, Christoph Wildburger and Stephanie Mansourian*

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# What Works in Conservation

William J. Sutherland, Lynn V. Dicks, Nancy Ockendon, Silviu O. Petrovan and Rebecca K. Smith (eds.)

*Do wind turbine modifi cati ons reduce bat fataliti es? Does adding topsoil increase the abundance of heathland plants? Are interventi ons to reduce road impacts on amphibians eff ecti ve? Do herbicides control invasive parrot's feather?*

*What Works in Conservati on* has been created to provide prac� � oners with answers to these and many other ques� ons about prac� cal conserva� on.

This book provides an assessment of the eff ec� veness of 1389 conserva� on interven� ons based on summarized scien� fi c evidence. The 2019 edi� on contains new material on bat conserva� on. Other chapters cover prac� cal global conserva� on of primates, peatlands, shrublands and heathlands, management of cap� ve animals as well as an extended chapter on control of freshwater invasive species, the global conserva� on of amphibians, bats, birds and forests, conserva� on of European farmland biodiversity and some aspects of enhancing natural pest control, enhancing soil fer� lity and control of freshwater invasive species. It contains key results from the summarized evidence for each conserva� on interven� on and an assessment of the eff ec� veness of each by interna� onal expert panels. The accompanying website **www.conserva� onevidence.com** describes each of the studies individually, and provides full references.

This is the fourth edi� on of *What Works in Conservati on*, which is revised on an annual basis. As with all Open Book publica� ons, this en� re book is available to read and download for free on the publisher's website at **h� ps://www.openbookpublishers. com/product/1031** where printed and ebook edi� ons can also be bought.