How do wind turbines kill bats?
Jeremy Hance, mongabay.com
August 25, 2008


Drop in air pressure, not collisions, devastate bat populations that fly by wind turbines



Numerous studies have shown that migratory bats are undergoing large fatalities due to wind turbines. Far more bats die due to wind turbines than birds, though they generally receive less attention. Now, researchers writing in Current Biology believe they know why bats are more susceptible to wind turbine fatalities.

It was long assumed that both bats and birds died by collision with the turbine. But the new study proves that 90 percent of bats felled by the turbine had died from internal hemorrhaging. The hemorrhaging is consistent with experiencing a sudden drop in air pressure. The bats' mammalian lung sacs over-expand when the air-pressure drops suddenly, exploding the capillaries around the lungs leading to death. It is not dissimilar from a scuba diver coming to the surface too quickly.

"Because bats can detect objects with echolocation, they seldom collide with man-made structures," explained Erin Baerwald of the University of Calgary in Canada. "An atmospheric-pressure drop 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."

Birds—who have more rigid lungs—survive such drops in air pressure, further explaining why bats die in greater numbers.

For the bat species that frequently encounter wind turbines—hoary bats, eastern red bats, and silver-haired bats—the fatalities present a large conservation problem. Bats have long life-spans—up to 30 years. But they don't reproduce annually and when they do their litter is usually only one to two pups, making them vulnerable to large population drops.

"Slow reproductive rates can limit a population's ability to recover from crashes and thereby increase the risk of endangerment or extinction," Robert Barclay from the University of Calgary said.

Bats play a vital role in the ecosystem by preying on insects, including insects that are common in agricultural fields. Their loss could mean a dramatic upswing in insect infestations.

Erin F. Baerwald, Genevieve H. D'Amours, Brandon J. Klug, and Robert M.R. Barclay (2008). Barotrauma is a significant cause of bat fatalities at wind turbines. Current Biology 18, R695–R696, August 26, 2008.

Related

Wind power takes a toll on migratory bats September 12, 2007
The danger of wind turbines to birds has long been known and well documented. Most recently several studies and articles have attempted to place the level of bird casualties in perspective: "More birds killed by cats than wind turbines". But lesser known—and lesser studied—is the effect wind turbines have on bat populations. Collisions between groups of bats and wind turbines have been observed at numerous turbines in America, Australia, and Europe. While these fatalities, sometimes killing hundreds of bats, have been seen for years, their cause remains unknown.









CITATION:
Jeremy Hance, mongabay.com (August 25, 2008).

How do wind turbines kill bats?.

http://news.mongabay.com/2008/0825-hance_bats.html