TCU researchers studying the effects of wind turbines on the bat population

Fort Worth, TX

Eastern Red Bats are largely loners. By day, they roost in tree branches where their reddish-brown fur could be mistaken for early fall foliage. Their long, narrow wings provide for rapid, but erratic flight. They can be been spotted around light poles, dining on moths.
Not much else is known about them, except that they are dying.
The Eastern Red Bat is among bat species apparently at risk from America’s rising reliance on wind power. Researchers first noticed bat carcasses littering a West Virginia wind farm back in 2003, but it didn’t take long to see the problem stretched beyond the Allegheny Mountains.
“As wind energy expands, these bats aren’t just being killed in the mountains of West Virginia,” says Amanda Hale, assistant professor of biology. “They are also being killed in the corn fields of Iowa, the wheat fields of Alberta and cow pastures in Texas. It’s a problem that’s on a big scale and it’s hard to quantify and figure out.”
Hale and her team of researchers at TCU are working on it. She and Kristopher Karsten ’00 MS, a postdoctoral associate, are leading a team of students who don hard hats and orange vests to help monitor bat and bird fatalities at Wolf Ridge, a wind farm with 75 turbines located on a high ridge just south of the Red River outside Saint Jo, Texas.
Their efforts are part of a unique partnership between TCU’s Institute for Environmental Studies, the University of Oxford and NextEra Energy Resources that is exploring the ecological, economic and social impacts of wind development. First announced in March 2008, the five-year research effort is working to not only broaden the scientific knowledge base of how wind turbines affect the environment, but also help develop solutions to better integrate them with wildlife and human populations.
The multimillion-dollar effort is funded largely by Next- Era Energy Resources, the largest generator of wind and solar power in North America. Headquartered in Juno Beach, Fla., it operates 115 facilities in 26 states and Canada.
Mike Slattery, director of the Institute for Environmental Studies, says the initiative has exceeded his expectations — in part because of the support from NextEra, which recently contributed an additional $250,000 to the project.
“They’ve been remarkably open and transparent,” Slattery says. “There are some difficult numbers coming out of Wolf Ridge in terms of bat mortality and never once has there been any notion of burying the data. They want to be proactive, to be part of the solution.”
Slattery also says the initiative has provided unique hands-on research opportunities for students.
“The ability to live on-site, go out to the field and collect data, then learn to deal with all the ups and downs of that has been very, very valuable,” he says. “We have not just graduate students, but undergraduates writing, collating and scrubbing the data. It’s been amazing to watch them be so engaged in the research process.”
When the TCU group started the Wolf Ridge research in 2009, they expected to find some bird carcasses around the turbines. They didn’t expect to find so many bats.
Searchers found 683 bats in two years of study — the majority Eastern Red Bats and Hoary Bats, followed by a small number of Evening Bats and Tricolored Bats. The numbers peaked between mid-July and September, which is when the Eastern Red Bats and Hoary Bats make their way south from the northern United States and Canada to spend the winter in the southwestern United States and Mexico.
Some scientists speculated that bats perhaps mistake the turbines for tall trees, or they think they might be light poles that will attract moths, a favorite meal. Maybe they’re just curious.
 When they get too close, the nocturnal creatures can get swiped by the blades, which at the tips, can reach speeds upwards of 120 miles per hour. Some bats appear to be killed by the blades while others may be sucked into a low-pressure area behind the spinning blades, rupturing the bats tiny lungs and causing internal bleeding.
It’s hard to pinpoint exactly how much wind farms are impacting bat populations because so little is known about some of these reclusive species. Unlike most birds, bats are nocturnal and are more challenging to spot. Also, certain species, such as the Eastern Red Bat, sleep high in tree limbs and rocky crevices, making them harder to find.
What is apparent is that bat populations are in jeopardy in many parts of the country, including Texas. According to Austin-based Bat Conservation International, more than half of all American bat species are in severe decline or already listed as endangered. Ed Arnett, conservation scientist and director of programs at Bat Conservation International, says bats aren’t covered in the Migratory Bird Treaty Act, legislation passed in 1918 that makes it unlawful to kill, hunt or capture migratory birds.
“Bats get little or no protection,” he says.
A world with fewer bats means they can’t provide as many services to the ecosystem such as pollinating plants and feeding on pests — including mosquitoes and crop-destroying beetles.

“There’s no question that there could be huge economic and ecological effects if we lose significant numbers of our bat populations,” Arnett adds.
Hale and Karsten knew the 683 dead bats found in the first two years of their research at Wolf Ridge weren’t all that were killed. The number was likely much higher.

After accounting for the bats they likely missed, Hale and Karsten estimate the body count at Wolf Ridge is much higher — numbering well into the thousands in 2009.
But last year they noticed the bat mortality appeared to be cut in half. They aren’t exactly sure why — perhaps it’s the overall population decline, or maybe the bats adjusted their migratory path away from Wolf Ridge. They also found relatively more Hoary Bats in 2010 compared to 2009. This year the research continues and Hale and Karsten are anxious to see if those trends hold.

 In February, the Wind Initiative’s annual advisory board convened on campus and Hale and Karsten shared their latest findings and discussed further proposals for research. Previous studies have found that a simple tweak on how the turbines are operated could have dramatic effects on bat deaths, so the team suggested following up on that research.
“Most bat fatalities occur on low-wind nights, when the turbines aren’t spinning that much and the energy companies aren’t making a whole bunch of money,” Hale says.
Wind turbines can be adjusted to turn at varying wind speeds, she says. In previous studies, turbines that come on when winds hit five or six meters per second, instead of the current three or four meters per second, reduce bat fatalities  by up to 60 to 70 percent.
“The idea is that when winds speeds are higher, it’s not as efficient for the bats to be out foraging, so they’re not flying or interacting with the wind turbines,” she says. “[The damage comes] at that low speed when they are out interacting with the turbines, unfortunately.”
The good news, Hale and Karsten say, is that the turbines aren’t producing that much power at low wind speeds anyway, so NextEra, which has revenues of more than $15 billion, wouldn’t have to take a huge financial hit.
“You would have a heck of a lot harder time convincing a wind energy company to cut back if mortality was highest at high-wind times, when they’re making the most money,” Karsten says. “The fact that it happens at such low wind speeds, when they’re not really creating a lot of revenue, that’s good from a biological conservation perspective.”
NextEra officials agreed to allow the team to curtail some turbine operations during the bats’ migration period. This summer and fall, TCU’s bird and bat team will do a series of tests on 24 turbines, altering how they operate with the goal of reducing bat fatalities.
“If these turbines are impacting bats, why are they impacting bats?” Slattery says. “It’s not just a matter of silly bats flying into blades, but why are they doing it? Is it the turbines or something else? What’s going on with their acoustical systems?”
This is another fascinating issue that Hale and Karsten will be looking at over the next two years.
Slattery adds that the beauty of the TCU Wind Initiative is that research is allowed to shift and change in order to find the best practical solutions. He says that’s crucial because as capturing wind energy grows, it’s increasingly important to understand the impact on the environment.
“We can’t let this run away from us and in 20 years time say, ‘I wish had thought of doing it this way’ or ‘What a pity we didn’t think about the impact of this.’ ”