Endangered bats are regularly being killed by wind farms despite efforts to reduce the risk, a study shows.
The mammals are fatally injured while hunting insects such as midges attracted by the heat that is generated by the spinning turbine blades.
Costly environmental tests called EcIAs (Ecological Impact Assessments) completed prior to their building have failed to stop the fatal collisions, say scientists.
In the first study of its kind in the world, which was partly commissioned by Scottish Natural Heritage and other quangos, researchers studied the death rates around wind turbines.
They studied 46 wind farms across the UK, 16 in Scotland, and found bats were being regularly killed in at least more than a third of them.
Now the team are calling for an overhaul in the assessments as they are poor predictors of future fatalities among bats.
In the UK the number of bats in areas where turbines are put up have fallen by 54 per cent.
The study found up to 64 bats a day are dying at wind farms, although this figure is “highly variable”.
Professor Fiona Mathews, of Exeter University, said: “The findings highlight the difficulty of establishing with certainty the effect of major developments before they occur. This is a real problem for the planning system.
“It’s difficult to say exactly how many bats have been killed by wind farms because it’s very difficult to work out.
“They are small and brown and Although some people may not like them they play a very important part in the environment. The tiniest can eat 5,000 midges a night.
“They also keep moths and caterpillars at bay increasing crop yields. So it’s something that affects us all.”
Ms Mathews said it is important now to determine whether bats might actually be attracted to wind turbines.
The most straightforward approach to keep bats safe is to minimise the rotation of turbines at night in the summer and early autumn when bats are most active.
Some operators are embracing this approach and she and her colleagues are working with them to test the method.
Bats can mistake wind turbines for tall trees because the air currents are similar.
Ms Matthews called for more thorough assessments prior to building along with careful study of casualties post-construction and their impact on local bat populations.
She said: “We need to remember bats have been around for at least 30 million years and during that time have been able to fly happily without the risk of colliding with a spinning object.
“If bats are actively attracted to turbines then it might not prove possible to predict this accurately in advance.”
“Our work highlights this can be difficult to achieve in practice as animals do not always behave the way we might anticipate.”
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