State officials say wind turbines in Pennsylvania killed about 10,000 bats last year. As the state strives to get 18 percent of its energy from renewable sources by 2020, researchers are working to figure out how to reduce the number of bats killed.
Most bats killed by turbines don’t get caught up in their blades like birds do—they die of barotrauma.
“It kind of equates to a scuba diver getting the bends, coming up too fast,” said Tracey Librandi Mumma of the Pennsylvania Game Commission. “The bats are basically getting close to these spinning turbines and then the pressure difference causes their capillaries in their lungs to explode.”
Ed Arnett of Bat Conservation International said that as demand for wind power grows in the U.S., he is worried about a rising death toll for bats. The bats play a vital role in eating insects that plague crops.
“When you start scaling up the impacts, that’s what gets alarming,” Arnett said. “Bats are very long-lived animals, but they’re slow to reproduce, and they’re very susceptible to localized population impacts and possible extinctions because of their reproductive strategy and their life history traits.”
Early studies in Pennsylvania have found that devices emitting high-pitched signals from turbines can keep bats away and cut down on deaths.
“It creates kind of a disorienting and almost an uncomfortable air space around the turbines. Theoretically, once they encounter that air space they would move away from it,” said Arnett.
Other studies have shown that keeping turbine blades stationary in low wind, when bats are most active, can reduce mortality as well. That is a difficult change for wind farms to make once they are already running, though, and Arnett doesn’t know of any U.S. companies doing it.
With no solid mitigation strategies yet available, Arnett said the best way to reduce the number of bat deaths is to build wind farms far away from hibernacula and migratory paths after doing preconstruction bat surveys.
Arnett says more research is needed to determine how off-shore wind farms, such as those in development of the coast of Delaware and New Jersey, will affect bat populations.