More than 600,000 bats may have been killed by wind turbines last year in the continental United States, according to a new study, illustrating the ongoing controversy over clean energy projects’ environmental impacts.
The study by University of Colorado, Denver, researcher Mark Hayes, to be published in the journal BioScience, used statistical models to determine the estimate from other researchers’ peer-reviewed data of bat deaths at 21 wind energy facilities across the United States.
Almost all wind energy facilities have reported bat deaths, the study said, with bats most often falling victim to trauma from wind turbine blades and air pressure changes caused by the fast-moving machinery. Hayes said the actual number of bat deaths could be as much as 50 percent higher because his study did not include states with some of the highest bat populations and used a conservative statistical model.
Estimating environmental impacts on bats is particularly challenging because of their small size and nocturnal behavior. As a result, few data exist on the size of their populations in the United States, the study said
Bats face unique challenges from wind turbines because their low fertility rate makes it difficult for the population to regrow. Most bats give birth to one baby per year, and also face threats from climate change and disease, Hayes said. Some researchers have suggested acoustic sound may prompt bats to avoid wind turbines, or if more research is done to predict under what conditions bats are most likely to be active, wind turbines could be switched off at that time, Hayes said.
Hayes’ estimate of bat deaths is higher than some previous estimates, although lower than research published earlier this year in the journal Wildlife Society Bulletin, which used previously unpublished data to estimate 888,000 annual bat fatalities. Hayes also found different areas had varying rates of bat deaths, with the Appalachian region seeing the highest rates.
Some industry officials have sought to downplay those figures, pointing to research backed by the wind energy industry like a March study that found the “ability to assess risk of a proposed [wind energy] site remains tenuous.”
“The wind industry has taken the issue of wildlife impacts, especially bats, very seriously,” said Frank Maisano of Bracewell & Giuliani, which represents wind industry clients.
In a statement, John Anderson, the director for siting policy at the American Wind Energy Association, said the industry was already taking steps to adopt tougher Fish and Wildlife Service regulations and to protect bat habitats by working with state and federal regulators.
Anderson noted that greenhouse gas emissions – not wind energy – posed a far greater threat to bat species.
“Adding wind power, as the most readily scalable form of clean energy, reduces those emissions more rapidly than any other energy option,” Anderson said.
Hayes said he didn’t mean the paper as an attack on wind energy, which he sees as viable.
“What I hope people take away from it is that there may be some fairly significant negative repercussions for some wildlife species,” Hayes said, though he thought the bat problem could be solved with further research and new technology.
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