Dousing just one of a wind turbine’s three blades in black paint dramatically reduced the number of birds the turbines killed in a multi-year study conducted in Norway, report Heather Richards and David Ferris for E&E News.
The study, published last month in the journal Ecology & Evolution, found that the turbines with one black blade killed 71.9 percent fewer birds than standard turbines on the same wind farm in the Norwegian archipelago of Smøla.
Jonathan M. Gitlin of Ars Technica reports that though wind turbines are an important part of many plans to generate renewable energy, some research has shown they can pose a danger to flying wildlife like birds and bats. The United States Fish and Wildlife Service estimated that roughly 300,000 birds were killed by wind turbines in 2015. Another study estimated wind power killed some half a million birds and more than 800,000 bats died in collisions with wind turbines each year.
Writing for BBC’s Future Planet, Brianne Hogan points out that these figures remain far lower than the total killed by powerlines in the U.S., which a 2014 paper estimated may be between 12 and 64 million. House cats, meanwhile, exterminate an estimated 1.3 to 4 billion birds annually.
Still, the potential of wind power to damage ecosystems by killing or disturbing wildlife has been a concern voiced by both environmentalists and those who more broadly oppose renewable energy. From the wind turbine's point of view, whacking birds to death can also damage the blades, which can be time consuming and expensive to repair, reports Alexandru Micu for ZME Science.
At the Smøla wind farm where the study was conducted, the researchers found that nearly 500 birds were killed by the site’s 68 turbines over a 10 year period, per E&E. After finding a 2002 study suggesting a single black blade may help deter birds the team decided to try it out on four turbines beginning in 2013.
In the following three years, just six birds were killed by the painted turbines, compared to the 18 killed by four nearby unpainted turbines, per Ars Technica. Speaking with E&E News, the researchers say the black blades may allow birds to visually recognize the spinning turbine as an obstacle by creating a “motion smear” that allows them to avoid the dangerous blades.
But the black-blade solution may only work in certain circumstances. "One cannot expect this solution to reduce fatalities of most other bird species because many causal factors contribute to avian collision mortality with wind turbines," Shawn Smallwood, a California ecologist who has studied bird deaths caused by energy infrastructure, tells E&E News. "Many birds, for example, collide with wind turbines at night, when tower colors are irrelevant."
The authors write that the study’s findings are also limited by the small number of turbines they tested, but add that the intervention should be investigated further.