Hundreds of bats are being killed in collisions with wind turbines in the UK each month, despite ecological impact assessments predicting that many windfarms were unlikely to affect such animals, according to a new study.

All UK species of bats are protected by law, and ecological impact assessments - carried out before construction of windfarms or other sites - should weigh up the risks for local habitats and wildlife. But new research suggests that such assessments are simply not up to scratch.

Using sniffer dogs, scientists at the University of Exeter report that they hunted for bat carcasses at 46 windfarms across the UK, 29 of which had ecological impact assessments available. For 18 of the sites the assessment reported that a windfarm would be unlikely to affect protected species, or an investigation into bat activity was unnecessary.

However the researchers found that nearly all of the 29 sites showed evidence of bat activity, while half had seen collisions between bats and wind turbines with estimated death rates of up to 64 fatalities per month, taking into account factors such as possible removal of carcasses by predators.

Among the sites flagged as posing a high risk to bats, the authors found that efforts to reduce the impact of wind turbines had had little effect.

“The sorts of mitigation that have been used, like moving the turbine a bit further away from woodland, just wasn’t doing the job,” said Dr Fiona Mathews, lead author of the research that was published in the journal Current Biology.



The authors conclude that ecological impact assessments do not adequately predict the risk of windfarms to bats. But it is not clear whether the failings are down to changes in the behaviour of bats after windfarm construction, or are simply down to poor surveying of the area beforehand.

“That is something that really needs urgent attention,” said Mathews. “At the moment tens if not hundreds of thousands of pounds are paid on infrastructure projects all the time to do ecological surveys with nobody actually doing any follow-ups to see whether they’re effective or not.”

As well as improving pre-construction surveys, the authors say that assessments should be carried out after windfarms have been built, while better approaches should be developed to reduce the chances of collisions - such as re-positioning the turbine blades out of the wind at night during periods in the year when bats are most active. More research is also needed into why the bats are flying so close to the turbines, said Mathews.



But, she adds, wind turbines remain an important source of clean energy. “What we want is something that actually works for conservation rather than it just being a box-ticking exercise,” she said.