Wind turbines have long garnered scrutiny for killing birds that fly into their spinning blades or tall towers. Much of the data about bird deaths at wind facilities in the United States comes from studies published in 2013 and 2014. Those studies gave a wide range for the number of birds that die in wind turbine collisions each year: from 140,000 up to 679,000.1 The numbers are likely to be higher today, because many more wind farms have been built in the past decade.2
Those numbers are not insignificant, but they represent a tiny fraction of the birds killed annually in other ways, like flying into buildings or caught by prowling house cats, which past studies have estimated kill up to 988 million3 and 4 billion4 birds each year, respectively. Other studies have shown that many more birds—between 12 and 64 million each year—are killed in the U.S. by power lines, which connect wind and other types of energy facilities to people who use the electricity.5
Other sources of electricity are also more lethal for birds than wind energy. A 2012 study found that wind projects kill 0.269 birds per gigawatt-hour of electricity produced, compared to 5.18 birds killed per gigawatt-hour of electricity from fossil fuel projects.6 That’s in part due to collisions with equipment (wind turbines aren’t the only energy infrastructure birds can fly into), but mostly because of the environmental impact of fossil fuels. Coal mining has torn down forests and destroyed habitat, and burning coal produces air pollution tied to acid rain and mercury contamination, which scientists have linked to bird health impacts like birth defects. But when it comes to bird deaths, the most significant impact from fossil fuels is their contribution to climate change, which scientists expect will be extremely dangerous for birds. The National Audubon Society estimates that about two-thirds of bird species in North America are at increased risk of extinction due to rising temperatures and changes to the habitat where they live.7
“When assessing electricity generation technologies, it’s important to evaluate against baseline generation alternatives, because electricity generation is a requirement of modern society,” says Michael Howland, MIT professor of civil and environmental engineering. “Fossil fuels contribute to climate change, increased air pollution, and negative impacts on human and animal health, including birds, among other issues. Wind energy is an electricity generation technology that significantly reduces such environmental and health impacts.”
Still, scientists and conservationists are actively working to minimize bird interactions at wind facilities. “Environmental impact studies” are conducted before the construction of large infrastructure projects, including wind farms, and are meant to ensure projects are not sited in locations that pose a risk to protected species. Researchers are still trying to understand all of the reasons why birds may crash into turbines, such as poor visibility or migration patterns.8 Some conservation biologists are studying how specific species and migration routes are affected by wind facilities, and if wind farms built in certain places may have an outsized impact on vulnerable bird populations.
There are also ways to build safer wind farms for birds. Before construction, wind companies survey sites, and can place fewer turbines in areas most important for habitat, or leave those areas alone entirely. Scientists have found that painting one blade of a turbine black, which can increase visibility, can reduce bird fatalities by more than 70 percent.9 And some wind companies are experimenting with using artificial intelligence to sense a bird’s approach, powering turbines down to avoid collisions.10
Thank you to Julie Grant of Rowland Heights, California, for the question. You can submit your own question to Ask MIT Climate here.
Visual aids for birds
Additionally, there are increasing initiatives to prevent bird strikes at wind farms. Bird deaths from turbines are far less common than deaths from domestic cats or collisions with cars, buildings, and power lines. However, given that many bird populations are declining, Tom Will, a conservation ornithologist who retired from the US Fish and Wildlife Service, believes that it is important to address any cause of mortality.
Furthermore, he notes that certain birds—like slow-reproducing predators that hunt in the same wide-open, windy spaces that are popular for wind farm development—are more impacted than others. According to Will, “any mortality is significant” for certain raptors, such as golden eagles, whose populations are either declining or barely stable. ”.
Will continues, “It can be helpful to avoid placing wind farms in high-risk areas, such as ridgetops, where many bird species congregate during migration and raptors in particular use the uplifting winds.” If avoiding bird activity is not possible, painting the turbine blades could be a relatively easy solution. YOU MAY ALSO LIKE.
This idea goes back to experiments that began in the late 1900s by the bird vision scientist William Hodos of the University of Maryland. He found that as American kestrels get closer to rotating blades, the spinning becomes too fast for their eyes to capture, producing an invisible blur. But Hodos discovered that painting a single blade black can make the turbines more visible to the birds. And sure enough, when scientists recently tested this approach in Norway, they found that black blades reduced death rates by 70 percent for 19 bird species.
The approach needs more testing, notes Shilo Felton, who leads the Renewable Energy Wildlife Institute’s wind-wildlife research program; the nonprofit is currently testing the painted blades at a large wind farm in Wyoming to see if it helps to avoid eagle collisions. And it’s possible that the strategy might need tweaking for offshore wind turbines, which are currently expanding in the UK and Europe, notes Alex Banks, an ornithologist working on bird conservation with the UK government’s conservation watchdog Natural England. For instance, many birds that forage at sea, like black-legged kittiwakes and lesser black-backed gulls, may be especially unlikely to see or avoid wind turbines.
“Their evolution, I suppose, hasn’t primed them necessarily to expect obstacles in their foraging space,” Banks says. These species may benefit from painting the turbine towers as well as the blades with noticeable patterns, he says.
Other solutions are also in development. Banks is involved in an effort to use laser-based tools and GPS tracking to measure the flying altitude of various seabird species. The goal is to inform offshore turbine developers so they can decide on turbine heights that reduce collisions with birds flying low above the sea. And at some offshore wind farms in the Netherlands, scientists are using a model to predict the passing of migratory bird species in advance, so the turbines can be turned off while the birds move through.
Meanwhile, back on land, the Renewable Energy Wildlife Institute is testing a system that uses video cameras to detect incoming eagles and other species, and then emits acoustic signals to deter them; the same system can be used to turn the turbines off. At some wind farms the institute partners with, humans go out and watch for eagles. If they see one, individual turbines posing a risk to the bird will be slowed or stopped.$[$PB_DROPZONE,id:knowable-newsletter-article-promo$]$
According to Weaver, some wind energy companies have voluntarily adopted existing mitigation measures or worked with scientists to develop and test new ones. However, more wind companies must act immediately; far too many only implement mitigation strategies like curtailment when absolutely necessary, as in the case of endangered or protected species.
It’s critical, Weaver says, to find ways of incentivizing companies to also protect common species, to help ensure that they don’t become endangered in the future. In countries where wind developments are funded by global banks, making mitigation a requirement for securing funds could also help, Bennett says. Stronger regulation across the board would be ideal, she adds; Germany, for instance, has long required all new wind turbines to practice curtailment to avoid unnecessary bat deaths.
“I think we can get to a solution,” Weaver says. But to get there, she says, will need discussions between local governments, wind energy companies, conservationists, and government agencies, as well as scientists, to make sure that new and current mitigation strategies are applied appropriately. “It’s going to take absolutely everybody coming to the table. ”.
Katarina Zimmer is a science and environment journalist currently based in Germany, with work published in Knowable Magazine, National Geographic, Scientific American, BBC Future, The Atlantic and elsewhere. Check out more of her work at www.katarinazimmer.com.
Katarina Zimmer is a science and environment journalist currently based in Germany, with work published in Knowable Magazine, National Geographic, Scientific American, BBC Future, The Atlantic and elsewhere. Check out more of her work at www.katarinazimmer.com.
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