Indiana wind turbines blades revolving slower to protect endangered bats

But for many of the real-life nocturnal mammals in Indiana, October also means migration season and a potential for mass killing of the animal by wind farms.

Between 600,000 and 900,000 bats are killed in the United States each year by wind turbines, according to a study published in the academic journal BioScience. Many are killed through collisions with whirling blades or through barotraumas, the technical term for internal injuries to an animal when it passes through low-pressure zone created in the wake of a spinning turbine.

“Wind farms really impact the migratory bats – they are getting absolutely hammered,” said Tim Carter, who runs Ball State University’s bat laboratory.

Though all migratory species of bats are susceptible, the deaths in Indiana are particularly damaging to the endangered Indiana bat and northern long-eared bat, which are already facing declining numbers because of the deadly white-nose fungal disease that is decimating Hoosier roosting areas.

Last year two Indiana bats and one northern long-eared bat were found to have been killed by wind farms across the state.

But wind energy companies are taking steps to mitigate the deaths during migration season by slowing or stopping the turbines between sunset and sunrise.

Wildcat Wind Farm, a 125-turbine farm in Madison and Tipton counties, applied for a Habitat Conservation Plan in August from the U.S. Fish and Wildlife Service that would require it to slow the turbines during the night and to purchase and provide for 253 acres of land for summer habitat.

In return, the company could receive an Incidental Take Permit, allowing the firm to legally kill a small number of the endangered species in exchange for taking steps to avoid more widespread deaths.

“Wildcat Wind Farm seeks to maximize production of non-polluting energy by the project, while conserving bats and minimizing and mitigating, to the maximum extent practicable, the impacts of any incidental take,” said Larry Springer, a public relations representative for Enbridge, the Canadian-based owner of the wind farm.

The Fowler Ridge Wind Farm, which operates 355 turbines in Benton County, worked with the U.S. Fish and Wildlife Service to develop a plan to reduce fatalities by 50 percent. The plan requires that turbines be shut down and turned perpendicular to the wind during low-wind times between sunset and sunrise.

Last year, 118 bat carcasses were found around turbines between Aug. 1 and Oct. 14, according to the company’s take report.

The idea behind Incidental Take Permits is to mitigate deaths while still allowing the clean-energy companies to operate economically, Georgia Parham, a representative of the U.S. Fish and Wildlife Service, said.

Parham said the plan accounts for the deaths of endangered species and, in effect, tries to make up for them through other conservation efforts — often through the upkeep of nesting grounds.

“It’s looking at the big picture and the long-term conservation of the species,” Parham said.

Incidental take permits are neither new nor novel to the wind energy industry. All types of industrial and construction projects often have to account for the unintentional deaths of endangered species.

“It’s something that is an option for any wind farm development in places where there are listed (endangered) species to be affected,” Parham said. “We work with quite a few wind energy companies in the Midwest.”

Without a permit, wind farm owners could be found liable and charged with harming an endangered species if an animal was found to have been killed by a turbine.

At the national level, the American Wind Energy Association (AWEA) released a set of best-practices guidelines in 2015 to go into effect this year that looked to reduce deaths by 30 percent. The practices call for stopping or slowing rotation during low-wind times, when bats are more likely to be flying.

“American wind power is strongly committed to producing one of the safest and cleanest forms of energy, for people and wildlife." said Tom Kiernan, CEO of the wind energy group.

Though the changes could cost wind companies millions in lost revenue, Kiernan said, “Our industry values all wildlife and habitat. By proactively employing this measure to reduce our already low environmental impacts further, consumers can have even more confidence in buying clean, affordable, and carbon-free wind energy.”

Carter said mitigation measures do make an impact.

“If we had had this conversation four years ago, I would have said wind farms are catastrophic for bats,” Carter said.

Though teams have tried practices such as using high-pitched whistles or bright flashing lights, the most effective way to reduce deaths that Carter has seen is simply slowing or stopping the blades.

“(Slowing the blades) has absolutely had a fantastic effect,” he said.

What is an Incidental Take Permit?

The permit, obtained through the U.S. Fish and Wildlife Service, allows a company to unintentionally kill or injure a small number of endangered animals. In exchange, the company must work to limit deaths and often provide habitats to make up for the lost animals.

To limit endangered species deaths by wind turbines, several companies are signing a best practices policy that limits speed at night during migration season between August and October.