Oct. 31, 2011

For years, wind power has stirred up controversy for its deadly effect on birds, but now researchers are concerned about its fatal attraction to another critter on the wing — bats.

Dr. Amanda Hale, Courtesy of TCU.

In 2009, Dr. Amanda Hale, assistant professor of biology at TCU, took on a research project to study the effects of wind power on birds and bats. The study is being done at Wolf Ridge Wind, a 75-turbine wind farm about 90 miles north of Fort Worth in Cooke County. The 5-year project is being funded by NextEra Energy Resources, the largest developer of wind energy in the U.S.

Hale, who has PhD in ecology with an emphasis in ornithology, said when she started the study she expected to focus primarily on the effects of wind power on birds. But when they began collecting data, they found far more bat carcasses around the turbines than birds. The first year they found 100 dead birds of various varieties, collected within a search site surrounding about a third of the turbines. They also collected the remains of 450 bats. 

“We just kept finding bats,” said Hale.

Bird fatalities have been a hot-button issue for wind farms for 30 years. According to a 2009 U.S.Fish and Wildlife Report, wind turbines kill an estimated 400,000 birds a year. Hale said compared to other hazards for birds that number is low. The American Bird Conservancy reports 160 million birds are killed every year by collisions with power lines, towers, windows, automobiles and urban light sources.
“In general, the mortality caused by wind farms is nowhere near what other sources do,” said Hale. 

However, Kelly Fuller, Wind Campaign Coordinator for the American Bird Conservancy, said the wind industry is rapidly expanding across the country, and it’s critical that it does so responsibly with regards to wild birds, especially vulnerable species like the whooping crane.  

“All the things add up,” said Fuller. “When another source of mortality is added, it’s a source for concern.”
Since the original wind farms were built, bird fatalities have been reduced by relocating the turbines out of major flyways and set back from ridges. The first turbines were built as lattice structures, which made them attractive perches while today blades are attached to a solid pole. Birds are also attracted to lights mounted on turbines, which are required by the FAA, but strobe lighting has been found to reduce the effect. 

Some wind farms have also started doing seasonal shutdowns during migratory periods. And tracking systems have been designed to trigger shutdowns when the number of strikes spike as a flock flies through.

The 262-foot wind turbines at Wolf Ridge Wind. Photo courtesy of Dr. Amanda Hale
Bats got on the radar of the wind industry in 2003 when a higher rate of bat fatalities than expected was discovered by researchers at a wind farm in West Virginia. As a result, the Bat and Wind Energy Cooperative was formed in 2003, partnering Bat Conservation International, the U.S. Fish and Wildlife Service, the American Wind Energy Association and the U.S. Department of Energy’s National Renewable Energy Laboratory, to study bats deaths at wind farms and offer solutions.
One thing the researchers are trying to figure out is what makes the bats attracted to wind turbines. Birds are known to run into things but bats with their excellent night vision and sonar typically are able to avoid collisions.  One theory was that they were eating insects near them. A video taken by a researcher showed the bats chasing the turbine blades. 

Hale said another theory is that migrating bats may be crashing into turbines because they’re not using their sonar on familiar routes. It’s similar to when we take a road trip twice a year and know where we’re going without looking at a map, she said. 

“They’re on cruise control.”
Another important finding, bats tend to die at turbines on low-wind nights when they are foraging or migrating.

“That lazy spin [of the turbines] is actually dangerous to bats.” 

A solution that Hale and her team are proposing is to program the turbines to stop spinning on nights when there are low wind speeds and when the wind is coming out of the northeast, a scenario typical for both migrating and foraging bats.
Researchers enter collection site to search for birds and bats around turbines. Photo courtesy of Dr. Amanda Hale.

There are still two more years to go in the study, which is only the second public study done on wind power’s effect on wildlife in Texas.    

While wind turbines alone would not wipe out bats, several bat species populations have been declining on the east coast do to a spreading epidemic known as white nose syndrome. The disease, which has spread as far south as Oklahoma, combined with fatalities from wind turbines could have a significant impact on an animal that plays an important role in our ecosystem.

Hale said bats are extremely important to humans because of their effectiveness in controlling insect populations. They consume millions of pests a year, including mosquitos, and play an important role in agriculture. A colony of 150 brown bats has been estimated to consume as much as 1.3 million pest insects a year, according to an article published in sciencemag.org in March of this year.

As white nose syndrome spreads, more Texas wind farms will likely have to take measures to prevent bat fatalities. 

“This has huge financial implications,” said Hale. “Bats are estimated to be worth 3 billion dollars to the agriculture industry in natural pest control. We still don’t know yet if these bat populations can sustain these significant losses.”

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