Scientists have known for years that wind farms are killing bats in large numbers, just as they kill birds, but had always believed thought that the spinning blades of the wind turbines were smashing the animals to death.
A study released in Current Biology this month reports the results of a study of 188 bats killed near a wind farm in Alberta, Canada last year. Researchers found that almost half of the animals had no external injuries, and that most of those that they dissected had suffered burst blood vessels in their lungs, suggesting that their deaths were caused by a condition called barotrauma.
When wind moves through a turbine’s blades, air pressure drops behind them. The lungs and blood vessels of bats quickly expand and burst when they wander into the low-pressure zones.
"As turbine height increases, bat deaths increase exponentially," said ecologist Erin Baerwald of the University of Calgary in Alberta, toScientific American. "What we found is a lot of internal hemorrhaging."
Baerwald notes that while birds are also killed by wind farms, their lungs are stronger and more resistant to pressure changes. They are typically killed after being hit by turbine blades, and not because of the air pressure difference.
Scientific American reports that it is not clear what can be done to prevent the bats’ deaths, other than stopping the turbines from operating at night, when the animals are most active.