Endangered bats are being wiped out by wind farms despite efforts to reduce the risk, an Exeter study shows.
The legally protected mammals are killed while hunting insects 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.
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.
“In most countries the system of Environmental Impact Assessment is based on the assumption accurate assessment of risks can be made in advance and so appropriate steps can be taken to avoid any adverse effects – or if the bad effects cannot be mitigated, then the development should not be permitted to go ahead.
“Our work highlights this can be difficult to achieve in practice as animals do not always behave the way we might anticipate.”
She said EcIAs cost tens of thousands of pounds – if not more – to carry out because people have to go out at night and during the day for a year, possibly more.
She said: “It ticks a box but like many conservation efforts is actually a waste of time.”
Her study found up to 64 bats a day are dying at wind farms although this figure is “highly variable.”
She said: “It’s difficult to say exactly how many bats have been killed by wind farms in 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.”
Her researchers surveyed 46 wind farms across the UK for bat fatalities over the course of a month.
It’s extremely difficult to find dead bats so they relied heavily on search dogs to locate casualties as well as using audio analysis to characterise bat activity.
Said Prof Mathews: “Without the dogs locating bat casualties is like looking for a needle in a haystack.”
Most bat species weigh less than five grammes.
She said: “Failure to survey adequately is a huge problem and explains why many wind farms apparently have ‘no problem.'”
The researchers then compared the bat activity and casualties they recorded to the expected impact at 29 of the sites for which an EcIA was available
That comparison showed the “perception of risk to bats during EcIAs was not significant in predicting either bat casualty rates or activity levels post-construction.”
The researchers also found the mitigation measures put in place at sites determined in advance to present a greater risk to bats have not provided adequate protection. Bats continue to be killed.
Prof Mathews said EcIAs might not be conducted in a sufficiently rigorous manner.
It’s also possible bats change their behaviour once wind turbines are erected.
She 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.”
Prof Mathews said it’s important now to determine whether bats might actually be attracted to wind turbines.
Meanwhile 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.
The nocturnal creatures are welcomed by farmers across the world as they eat large numbers of insects that usually damage crops.
This reduces the amount that farmers have to spend on pesticides and saves millions of new plants that could be obliterated by the creepy crawlies.
Over 600,000 bats were killed by wind turbines across the USA in 2012 alone and in the UK the number of bats in areas where they are put up have fallen by 54 per cent.
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