Wind farms are killing about 200 bats a month in the UK, say scientists who have called for turbines to be turned off at night to save the creatures.
Bat-friendly operators who agreed to take such a step should be paid more for the electricity they generate, said Fiona Mathews, a biologist from Exeter university who led a government-backed study of 29 onshore wind farms.
Some wind farms were already testing night-time switch-offs and researchers were watching to see what effect this had, she revealed. “This approach obviously affects electricity generation, though to a lesser extent than one might imagine since the time that bats are at most risk is during low wind-speeds in the summer” when turbines generate relatively little electricity, Ms Mathews added.
The study showed 194 bats were killed per month, based on carcases found underneath the turbines. The actual number could be higher because scavengers may have removed some bodies.
The researchers said more work was needed to find out why bats ventured so close to the farms. It is thought the animals might be attracted to insects around the blades, or may switch off their sonar at the height of the blades because they are not used to confronting objects of that size.
“Bats have been around for at least 30m years and during that time have been able to fly happily without the risk of colliding with a spinning object,” said Ms Mathews.
Erecting gigantic bat-proof nets around the turbines would be no solution because it would interfere with wind flows, Ms Mathews said. US researchers had also run into difficulties when experimenting with loud sounds to repel the animals, partly because the electricity needed to power the speakers was a significant drain, she added.
One wind farm operator said although he was unaware of any bat deaths near his company’s projects, he was not sure that it would be politically possible to pay generators to turn off turbines.
“If we are not generating power we should not get paid,” said Rod Wood, managing director of the Community Windpower group, which has eight Scottish farms operating or under construction.
The new study showed the main bat casualties were two common species, the common pipistrelle and the soprano pipistrelle, tiny bats with reddish-brown coats and blackish-brown ears. But researchers also found a dead migratory Nathusius’s pipistrelle, which they said raised concerns about whether onshore and offshore wind farms could pose a threat to navigation routes.
“These animals will be encountering multiple on and offshore wind farm sites as they make their way from eastern Europe along the north coast of continental Europe and across to the UK,” said Ms Mathews.
Another author of the study, to be published in the Current Biology journal, said that although wind farms killed bats it was important to remember the wider benefits of renewable energy, which boosted biodiversity by reducing the greenhouse gases that drive global warming.
“It is important that this is put into context alongside the many other causes of bat mortality caused by humans, including collisions with vehicles, kills by domestic cats, and range contraction due to climate change,” said Paul Lintott.
The researchers said that although huge amounts of money were spent to assess environmental risks before wind farms were built, this work was “very poor” at identifying whether a site was likely to be risky for wildlife once a wind farm was operating. “We therefore call for a switch in emphasis from pre-construction to post-construction assessments,” said Dr Mathews.
The research was funded by the government-backed Natural Environment Research Council and drew on data collected in separate studies funded by the environment and energy departments.
RenewableUK, the wind industry trade group, said it had been working with the government and conservation groups for years to better understand bat activity around wind farms and carried out “rigorous assessments” to make sure projects were as safe as possible.
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