More than 600,000 bats may have been killed at wind farms in the continental U.S. last year. That’s a lot for these flying mammals, which are already suffering from a virulent disease and climate change.
At wind farms, bats are most often killed when they are struck by spinning turbine blades. They may sometimes die from a sudden change in air pressure, which harms their respiratory systems.
A recent study has found that more than 600,000 bats – possibly up to 900,000 – died at wind farms in 2012. The study will be published in the journal BioScience.
Study author Mark Hayes said those numbers could add up over the years.
“That additional mortality has the potential to substantially reduce populations,” Hayes said.
The American Wind Energy Association, an industry advocacy group, said it follows siting guidelines from the U.S. Fish and Wildlife Service to help minimize bat deaths. The group joined with researchers and conservationists in 2003 to form the Bats and Wind Energy Cooperative, which researches bat activity before and after wind turbine construction and bat deterrents.
Hayes said preventing bat deaths at wind farms should be easy.
One challenge is that researchers don’t know the number of bats of individual species in the U.S. Hayes said bats most often killed at wind farms are migratory tree bats, which usually travel across regions in large numbers in the fall.
Hayes said bat mortality at wind facilities is one of the biggest problems facing bat conservationists right now – the other being white nose syndrome, a fungus that has wiped out entire hibernating bat colonies in the eastern half of the country.
Cris Hein coordinates the wind energy program for Bat Conservation International. He said the eastern red bat, the hoary bat and the silver haired bat are most affected by wind turbines. The latter two species fly through Washington and Oregon.
“Here in Oregon and Washington hoary bats and silver haired bats make up almost 97 percent of fatalities,” Hein said. “These are bats that move into our region and go as far as Canada during the summertime, and then migrate south in the winter.”
Study author Hayes said the Appalachian Mountains have the highest estimates of bat deaths.
Hein said fatality rates are much lower in the Pacific Northwest because most wind farms are not sited near trees, where bats roost as they migrate.
“Our concern right now is that as wind development creeps into the Cascades or the coastal range, more forested areas, we may see fatality rates similar to the east,” Hein said.
Study author Hayes said he thinks researchers will find a way to prevent most bat deaths at wind farms relatively soon.
One solution is to change the speed that turbines begin spinning. Another is to send out acoustic signals that would cause bats avoid wind farms. Researchers are testing both of these techniques now.
“This is a phenomenon that we know when it’s going to happen, and we know where it’s going to happen. It’s going to happen at night, and it’s going to happen in close proximity to wind energy turbines,” Hayes said. “If we can combine that information with a little bit of fine tuning and knowledge of where the bats are going to be at a particular time of year, I think we can design some reasonably effective solutions.”