The Winds of Change Bring Peril for Bats

Wind power is on the rise and with it is an uptick in bat deaths.

Developing renewable energy is critical to minimizing greenhouse gas emissions and reducing climate change. Wind energy is an important source of American renewable energy and the success of this industry is crucial to our green energy future. However, like all energy types, wind energy is not without its challenges. In the early 2000s, researchers realized that wind turbines were killing bats at record rates.

A Fatal Attraction

Findings from the last decade reveal that wind turbines kill more than half a million bats each year in the United States. The overwhelming majority of the bats killed are migratory bats that are not affected by white-nose syndrome, the pathogenic fungus causing precipitous declines in hibernating bat species.

Wind turbine blades disproportionately strike these migratory bats as they pass through wind farms to forage or migrate. It’s unclear why there are so many collisions, but bats are well-known to be curious creatures and have been documented to change course to check out turbines. Although there’s no scientific consensus on why bats are attracted to turbines—theories range from mistaking turbines as trees for roosting, to seeking out insect prey that congregate near turbines—this behavior puts them at increased risk for collision with the spinning blades.

Bat Numbers Give Us Cause for Pause

As more information becomes available about the interaction of bats and wind energy production, scientists are growing increasingly concerned. Bats are long-lived mammals (many bats live more than a decade, and at least one Brandt’s bat lived for 41 years!) that reproduce slowly, meaning that bat populations are very sensitive to losses of breeding-age adults.

A recent study led by UC Santa Cruz professor Winnifred Frick, whose findings were published in Biological Conservation earlier this year, set out to  identify whether mortality from wind turbines could cause bat populations to decline. Professor Frick and her colleagues focused on the bat species most commonly killed by wind turbines: the hoary bat.

The hoary bat, named for its silver-tipped fur that resembles hoar frost, is a wide-ranging, migratory bat found throughout the United States, into Mexico and Canada. Hoary bats are solitary animals, spending their days roosting in trees until sunset. As it gets dark, these charismatic critters emerge to feed, foraging over great distances as they search for moths and other insects.

Unfortunately, hoary bats seem particularly susceptible to wind turbines, representing over a third (38 percent) of all bats killed at wind energy facilities. Professor Frick and her colleagues sought to determine whether the high mortality rate for hoary bats at wind facilities was sustainable.

Their results were alarming. According to the best available estimates for population size and growth rate, they projected hoary bat populations would decline by 90 percent in the next 50 years due to mortality at wind turbines. If wind energy development continues at expected rates and nothing is done to decrease bat mortality, the fate of the hoary bat will only become more dire.

Unfortunately, the hoary bat is not alone in facing such a bleak future – other migratory bat species may also be at risk. While hoary bats are the hardest hit bat species, other species of migratory bats are also frequently killed by wind turbines. Hoary bats, eastern red bats, and silver-haired bats collectively account for almost 80 percent of all bats killed at turbines. Future research is needed to determine whether there are population-level impacts to eastern red bats and silver-haired bats from wind energy.

What Can Be Done?

Fortunately, there are techniques that the wind industry can adopt so that we do not have to choose between wind energy and these important bat species. Wind industry leaders have stepped up and are proactively working with researchers and government agency staff to create technological solutions to overcome these bats’ fatal attraction to turbines. Technologies to deter bats from approaching turbines, such as playing high frequency noises, lighting the blades with ultraviolet light, using textured turbine coatings, are in development and being tested at pilot sites. We are optimistic that these technologies will be commercially available within the next five years or so, but continued funding and research are needed.

Until these technologies are available, operational changes, such as “feathering” turbine blades so that they don’t spin at low wind speeds (when bats are most active) during important migration periods, can drastically reduce bat deaths. These operational changes can be adopted immediately, but they come with a catch: they reduce the amount energy being produced from each turbine.

It’s not that wind facility operators don’t want to do the right thing–most are aware of the problem and want to minimize bat kills. However, until there is industry-wide adoption, any wind facility that does implement operational curtailment (by strategically feathering turbine blades) is at a competitive disadvantage because it would be producing less energy than a comparably-sized facility that’s not endeavoring to protect bats. In addition, some facilities are contractually obligated to produce a certain amount of energy that leaves little room for seasonal curtailment to protect bats.

If wind facilities trying to protect bats go out of business, that’s a losing scenario for both wildlife and the climate. Thus, saving these bats can’t solely rest on industry – energy consumers need to value wind operators who take measures to protect bats.

It’s a rare opportunity to be able to protect a species before it’s on the verge of extinction, but in order to do any good, we must act swiftly. Allowing hoary bat numbers to continue to decline at a precipitous rate isn’t just bad for bats, it’s bad for industry, too. Protecting bats through preventative solutions available to us now will help keep these species off the Endangered Species List, at which point options may be limited to more expensive conservation measures.

Unlike Vampires, Bats Don’t Live Forever (Plus Vampires are Fake)

Time is of the essence and we cannot afford to delay action. The wind industry, conservation organizations, academia, government, and energy users need to work together to find solutions. Defenders of Wildlife is fully committed to a strong wind energy future while conserving bats. We are working to educate corporate buyers about the importance of purchasing wind energy from responsible operators, while simultaneously advocating for federal, state, and private investment to advance and commercialize technical solutions to reduce the industry’s impacts on wildlife. Tackling this issue now is critical to securing a strong future for the wind energy industry and bats.

Follow us on social media to stay up-to-date on the latest developments concerning wildlife from Capitol Hill and other news important our work. Don’t forget to sign up for our emails where you will get all the latest news and action alerts to support wildlife.