A Washington State University Vancouver researcher has helped develop a model aiming to predict the number of birds that would be killed by a wind farm if it’s built.
The study, led by WSUV assistant professor of statistics Leslie New, uses three basic parameters — hazardous footprint, bird exposure to turbines and collision probability — to develop a range for the number of fatalities expected at a given site. The research focused on golden eagles, a protected species, but could be applied to other species, New said.
The study was completed in partnership with the U.S. Geological Survey and the U.S. Fish and Wildlife Service.
“The goal with this is to try to avoid some of the really dangerous spots in advance,” she said.
Bird deaths can be a touchy subject for wind farms and wind energy advocates. Operators are sometimes reluctant to discuss data on existing facilities. But fatalities are known to happen when birds collide with the rotating blades of a wind turbine.
It can be difficult to know exactly how many bird deaths a proposed wind farm may cause while it’s still under review, New said. The only way to know for sure is to build it and observe it, she said. But by then, it’s unlikely that the problem will be fixed.
“You’re not going to take it down and move it if you’ve built it in the wrong place,” New said.
Using the statistical model to predict the number of fatalities in advance could give wind companies and regulators better information to prevent them, New said. That might mean relocating or removing a section of turbines most likely to conflict with bird activity, she said. It might mean curtailing operations at times when birds are most active in the area, she added.
Bird deaths vary widely depending on several factors, including location, size and wildlife activity. The Altamont Pass wind farm in central California — one of the facilities used in the study — kills dozens of eagles each year. Other wind farms may only account for a handful of eagle deaths per year, New said, and that’s more typical.
“Most locations will have some fatalities, but not overwhelming numbers,” she said.
There’s no federal requirement for reporting bird fatalities to the U.S. Fish and Wildlife Service. But permitting requirements vary from state to state, and some require more thorough environmental review than others.
USFWS can issue permits allowing eagle fatalities, and has in at least one case, said Michael Green, a deputy division chief with the agency in Portland. (It’s illegal to kill or possess a golden eagle.)
USFWS has used the statistical model to predict bird deaths at wind farms for some time, Green said. Having it now peer-reviewed and published only gives it more weight, he said.
Though there is occasional push-back from a wind company that disagrees with a mortality estimate, “we still believe we’re using the best science and being objective,” said Green, who works with the USFWS migratory birds and habitat program.
Washington and Oregon are among the nation’s leaders in wind energy. The states rank ninth and seventh, respectively, in total capacity with more than 3,000 megawatts installed each, according to the American Wind Energy Association. Much of that development has occurred near the Columbia River Gorge within the last decade.
New said she has already received inquiries about the model and applying it elsewhere. The study was published in July in the scientific journal Plos One.
Researchers hope the model makes it easier for policy makers and wind companies to evaluate the impact of a facility, New said. There’s inherent variability, she said, and the study recognizes that.
“Every site is different,” New said. “Not every project is as risky as another.”