Scientists at the University of Calgary have discovered that bats can die from a lowering in the air pressure close to the blades of the turbines which causes fatal damage to the bats' lungs. A similar condition is called the bends in humans and can occur during ascents and descents by divers and airline passengers.
"As a turbine blade goes around, it creates lift—like an airplane's wings—and there is a small zone of [dropping] pressure, maybe a meter or so in diameter, on the tips of the blades," explained Erin Baerwald, a doctoral candidate at the University of Calgary, in Alberta, who led the research.
"Bats fly through this area, and their lungs expand, and the fine capillaries around the edges of the lungs burst," Baerwald said to the National Geographic.
The team found that as bats use echolocation (radar) when they fly, they rarely fly into structures as big as wind turbines, however their study of bats found in Alberta, Canada found no contact with the blades, they report in Current Biology journal.
"An atmospheric drop in pressure at wind-turbine blades is an undetectable - and potentially unforeseeable - hazard for bats, thus partially explaining the large number of bat fatalities at these specific structures," said Baerwald.
"Given that bats are more susceptible to barotraumas than birds and that bat fatalities at wind turbines far outnumber bird fatalities at most sites, wildlife fatalities at wind turbines are now a bat issue, not a bird issue."
The researchers found that, as the bats fed on insects which do damage to crops, their deaths could have a negative impact on surrounding agriculture.
Wind industry officials have said they will do all they can to reduce the deaths of the bats but concede the task is difficult as little is known of the habits of the nocturnal creatures.
"It's a huge challenge," says Jason Edworthy, director of stakeholder relations for TransAlta Wind said to Canwest News Service. The company operates Summerview Wind Farm where close to 700 bats die each year.