Wind turbines killed hundreds of thousands of bats in 2012 in the United States, according to an article by Mark Hayes of the University of Colorado. Hayes took the number of dead bats from 21 wind turbine locations and inferred the number of nationwide bat deaths, arriving at the conservative estimate of 600,000 bats killed in 2012. But the real toll, Hayes notes, may be as high as 900,000.
Bats are killed by collisions with wind turbine blades or from air pressure changes caused by the blades, the latter being the real danger. Similar to the bends in scuba divers, barotrauma causes bats to pop from the inside.
“There are bats with no broken bones or other evidence of blunt trauma, that have pulmonary and middle ear hemorrhages which implies that they had suffered barotrauma,” Melissa Behr, a vet at the University of Wisconsin told the Telegraph in September (Behr wasn’t involved in Hayes’s research). “In one case 46 percent of the bats that were seen had no physical sign of trauma, but 100 percent had pulmonary hemorrhage.”
Because bat populations are also under threat from climate change and white-nose syndrome (a fungal infection that has killed millions of bats since 2007), and because most bats only give birth to one young per year, Hayes says the addition of wind turbines to the bat-killing mix is worrisome. Although few people have a love for bats, they’re the primary consumers of insects in some regions. Bats are particularly beneficial to farmers, who spend billions of dollars a year on insect suppression services, according to the U.S. Geological Survey. Fewer bats means more insects and higher pest-control bills.
It isn’t just bats wind turbines are killing in large numbers. In a study published earlier this year in the Wildlife Society Bulletin, author K. Shawn Smallwood estimated that 573,000 birds were killed by U.S. wind turbines (as well as 888,000 bats). In another 2013 study, published in the Journal of Raptor Research, biologists from the U.S. Fish and Wildlife Service estimated that wind turbines have killed 67 golden and bald eagles in the last five years.
Hayes’s article, titled “Bats Killed in Large Numbers at United States Wind Energy Facilities,” was published in the latest issue of BioScience.