Hundreds of bats are being killed by wind turbines, possibly because they are lured in by insects flying around the blades, scientists at the University of Exeter say.
But simple changes could prevent the bat deaths, the researchers said.
They studied 29 wind farms, using dogs to sniff out the corpses, and found that 194 bats were killed a month.
Because some of the bats will have been eaten by scavengers, or may have flown outside the search area, the number is probably higher, the researchers said, in work published in the journal Current Biology.
Dr Fiona Mathews of Exeter University, who led the research, said that simple measures such as turning off turbines at night at peak times for bats could save many bat lives.
She suggested that wind-farm operators who take steps to prevent bat deaths should be rewarded with higher tariffs for the electricity they produce.
Dr Mathews said more research was needed into the behaviour of bats after turbines were built, including whether they may “switch off” their sonar when flying at the height of the turbines because they are not used to encountering objects at that altitude. They could also be attracted to insects flying around the turbine blades.
“There are effective ways of preventing bat deaths,” she said. “Unfortunately we have found that assessments conducted when wind farms are being planned are very poor at identifying whether a site is likely to be risky. This means that appropriate action is not taken to protect bats.
“We therefore call for a switch in emphasis from pre-construction to post-construction assessments, so that any problem can be nipped in the bud early on.”
Two species of bats were the main casualties of wind turbines were: the common pipstrelle and soprano pipistrelle, tiny bats with reddish-brown coats and blackish-brown ears.
Bodies of the noctule, one of the larger European bat species which sometimes come out before sunset to feed on moths, beetles and other large flying insects, were also found around turbines.
A dead Nathusius’s pipistrelle, which has recently been found to be migratory, was also found, raising concerns about whether onshore and offshore wind farms could pose a threat to their navigation route.
“These animals will be encountering multiple on- and off-shore wind farm sites as they make their way from Eastern Europe along the north coast of continental Europe and across to the UK,” Dr Mathews said.
She warned that expensive ecological impact assessments carried out before wind farms were built often failed to assess accurately the true threat to bats.
“An open field might not be very interesting, whereas once new structures are built the bats may investigate it or feed around it.”
Dr Paul Lintott, first author on the Current Biology paper, said that although wind farms do kill bats it is important to remember the wider benefits of renewable energy in reducing greenhouse gas emissions and the positive impact that this will have on global biodiversity.
“Although bats are killed by wind turbines 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.
“By focusing resources on stopping turbines during high risk periods we should be able to minimise the collision risk to local bat populations whilst also benefiting globally from the transition to a greener economy.”
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