Understanding wind turbine impacts on wildlife

Today you’re hearing from Meagan Racey, who handles public affairs and media relations for Ecological Services, on her recent visit to a Vermont wind project.

Have you ever stood under a wind turbine, stared upward along an almost 300-foot pole, and been hypnotized by the rhythmic “whoosh, whoosh” of the white spinning blades slicing through a deep blue sky?

Up until earlier this month, I had not. So, I jumped at an opportunity to tag along with some of our staff on a visit to a 16-turbine wind project in Sheffield, Vt. We spent the day discussing wind power effects to birds and bats with staff from First Wind, Vermont Department of Environmental Conservation, Bat Conservation International, Theodore Roosevelt Conservation Partnership, and Texas Tech University.

The independent, Boston-based First Wind has operated the Sheffield Wind project atop Granby Mountain and Libby Hill since October 2011; the project has a maximum output of 40 megawatts and produces enough energy to deliver power to about 15,000 Vermont homes through three utility companies.

One of the Sheffield wind turbines. Credit: USFWS

One of the Sheffield wind turbines. Credit: USFWS

Fatalities of bats and birds have been recorded at wind facilities worldwide, and bat fatalities at wind facilities along the eastern U.S.’s mountain ranges are considered especially high. Studies show that bat fatalities peak during the late summer and early fall when bats migrate between their summer habitat and wintering areas.

Factors that appear to influence bat mortality at wind turbines include where turbines are sited, when and how turbines are operated, and a variety of environmental variables such as wind speeds, temperatures and storm systems. Some studies are even exploring the possibility that bats are attracted to turbines, and that attraction may result in their deaths if the blades are moving. Similar factors appear to influence bird fatalities, though lighting issues may also play an attractant role.

The hoary bat, pictured above, the eastern red bat, and the silver-haired bat are three migratory tree-roosting species that compose the majority of bats killed at wind facilities in North America. Credit: USFWS

The hoary bat, pictured above, the eastern red bat, and the silver-haired bat are three migratory tree-roosting species that compose the majority of bats killed at wind facilities in North America. Credit: USFWS

A graduate student at Texas Tech University, Colleen Martin, has just begun studying the turbines’ impacts on birds and bats there. This study is a terrific collaboration between the wind industry, a non-governmental organization, federal and state government agencies, and the research community. We are hoping to learn a great deal from her findings. The Service has provided both funding and technical assistance to this project in order to develop science that is applicable to other similar projects.

For Colleen’s study, the company has made adjustments to their turbine operations. During summer and early fall nights, half of the turbines will only operate when winds are above certain speeds or air temperatures are below certain levels. These curtailment levels relate to the periods when bats are most active.

Research by one of Colleen’s professors, Dr. Ed Arnett, shows that turbine curtailment is effective in reducing fatalities by up to 50 to 87 percent. Colleen will compare the fully operating turbines with the curtailed turbines to see if bat fatalities are reduced during these adjustments, and she will estimate total mortality using data from daily searches for bats and birds.

The curtailment and monitoring sound simple enough, but there are many details to ensure the research addresses all of the variables at play. To demonstrate that, Colleen took us on a tour of the wind project and walked us through a daily search.

Searchers have to follow a certain path leading from the turbine and keep their eyes peeled for carcasses. It might seem easy, but check out the example below of a bat by one of the turbines. On those cleared pads, a bat carcass can look a lot like a small pile of sticks and dried grass, and on pads where the ground is covered by plants, it’s even harder to see the body of a tiny bat.

This image of a bat by a wind turbine (see bottom left) illustrates the challenge of seeing bats on wind turbine pads. Credit: USFWS

This image of a bat by a wind turbine (see bottom left) illustrates the challenge of seeing bats on wind turbine pads. Credit: USFWS

My colleague, biologist Susi vonOettingen, pointed out that not only are the bats hard to find, but “you can’t talk or text or day dream while walking hour after hour with your eyes pointed to the ground. It takes intense focus and patience, and a good strong back!”

Colleen’s research has to factor in the efficiency of the searchers in finding carcasses. She also has to factor in the rate at which scavengers, such as raccoons or carrion beetles, remove dead bats or birds below the turbines.

The wind turbines are also equipped with loads of sensors that measure many variables including wind speed, turbine speed, and temperature. Once all of the ground searchers are done, Colleen will compare what the searchers find with information from the turbines to see what patterns emerge.

The Service is working with the wind industry to apply our available science to help determine project siting and operational measures so that they minimize impacts to wildlife, but research like Colleen’s is going to help us be even more specific in providing technical assistance to wind projects.

Colleen talking with the group at one of the sites where a bat was found. Credit: USFWS

Colleen talking with the group at one of the sites where a bat was found. Credit: USFWS

Her three-year study is currently one of a few that looks at the effects of curtailment beyond one to two years. We hope that it will further improve predictive models that estimate wind turbine fatalities in the Northeast, and will also add to the existing body of research testing the impacts of curtailment on bat mortality.

Our dedication to minimizing the impacts of wind energy on wildlife is further demonstrated through the Service’s land-based wind energy guidelines, efforts to help site projects, plan operations, and conduct research, and coordination under various federal laws, such as the Endangered Species Act.

Want to learn more? Check out the two wind projects that have proposed to alter operations at their projects in Maryland and West Virginia and implement conservation projects to minimize and mitigate impacts to endangered bats.

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