Conserving Europe’s bats with evidence: updated


Evidence to help practice

An updated bat ‘synopsis’, launched by Conservation Evidence, looks at the evidence for 190 ways to conserve bats. The bat synopsis gathers, organises, and summarises studies on the effectiveness of different ways to conserve bats, from bat boxes to legal protection, and is free to read or download from the Conservation Evidence website (www.conservationevidence.com). The original bat synopsis was published in 2013, and updates are expected to be regular from hereon in, to incorporate new knowledge. For those unfamiliar with Conservation Evidence, it is a longstanding project to collect and summarise the evidence for what works – and what doesn’t work - to conserve all species, and all habitats, globally.

The synopsis includes studies if they test an action that could be put in place for conservation, in an experimental or quasi-experimental manner, and have a measured outcome on bats. The original bat synopsis found 101 studies published before the end of 2012; the update has 173 papers published by the end of 2017 – for the first time also including studies originally published in Spanish and Portuguese.

Conserving bats in Europe

There are about 80 studies from Europe which test over forty different actions within the bat synopsis, meaning that European bat conservationists can draw on a wealth of knowledge from across the continent. This action spans from the very small scale, such as altering microclimate within bat roosts, to the far larger scale, such as legally protecting bats during development.

To begin at the large scale, three studies from the UK found that legally protecting bats during development was not sufficient to stop their roosts from being destroyed. A review found that 68% licenced activities involved bat roost destruction, while just over half a percent of compensation roosts were used by the same or a greater number of bats. Development licences are on the increase, with licences more than doubling in just three years from 2012-2014. The vast majority (81%) of licensees in the UK did not test whether bats were using compensatory structures. This sobering look at the limited effects of legal protection in the UK underlines the need for mitigation practices to be evidence-based and effective.

We can look at the success (or otherwise) of replacing roosts on a study by study basis, identifying the characteristics of replacement roosts that have worked and those that haven’t. For example, a review found that 74% of bat lofts were used, compared to only 13% of bat boxes, when replacing an existing roost in the UK. Roosts that maintained similar bat numbers, or even higher numbers, in Europe included two entire bat buildings plus one bat box in Spain, and a bat loft in Ireland; these projects could be studied and replicated in appropriate conditions. The 39 bat box studies collected in the synopsis also describe the features of successful - and unsuccessful - bat box schemes, while several studies assess ways to control the roost microclimate to benefit bats.

Other actions that were reviewed included ways to mitigate against damage to bats by wind turbines, roads, and lighting, where some actions were found to reduce impacts. For example, increasing the ‘cut in speed’ at which wind turbines become operational worked to reduce fatalities, in research from the USA and Canada. Underpasses under roads were used in varying proportions in five studies in Europe; effectiveness appears to vary with location and with underpass size, and some species appear more inclined to use them than others. Varying lighting affected different species differently. Switching from white to red light increased the activity of Myotis and Plecotus spp. to the levels seen in darkness, while Pipistrellus species hawked around the white lights; lowering the intensity of lighting led to increased activity for lesser horseshoe bats Rhinolophus hipposideros and soprano pipistrelles Pipistrellus pygmaeus, but not for Myotis spp; while adding UV filters did slightly increase soprano pipistrelle activity, but neither light nor darkness affected common pipistrelle Pipistrellus pipistrellus activity in the same study. While more research is needed to support conservationists in making decisions, existing studies can help to reduce impacts of developments.

Other concerns for bat conservation in Europe involve farming and forestry. While there are some significant evidence gaps, the new bat synopsis brings together some interesting results. Most farming changes did not bring about large results; while reducing chemical use did increase bat activity and alter the species composition in a study in Portugal, overall organic farming did not have consistently positive effects on bats in Europe, and nor did agri-environment schemes. Forestry found some more effective solutions; reduced impact logging did reduce the impact on bats compared to conventional logging, although only one study was from Europe; and retaining riparian buffers in logged areas also retained bats along those corridors, although these studies were not European. We need more effort to find good solutions to conserve bats in different land uses.

Hibernating pond bats by John Altringham

Hibernating pond bats © John Altringham

Share your knowledge

The new bat synopsis does not have all the answers on how to conserve bats, but the existing evidence should challenge our thinking, make us question ‘common sense’ solutions, and spur us to innovate new solutions and to test what we do more rigorously. This synopsis will now be updated on a regular basis, but is only as good as the studies it finds. We need scientists and conservationists to conduct more good quality studies on conservation actions; only with this data can we identify effective solutions, and modify or ditch the bad ones.

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