Hoary bats like this one are the species most often killed by wind turbines in Canada. ©Nessie Grace A bat lies dead beneath a wind turbine in southern Ontario. ©Mike Anissimoff

Each wind turbine in Canada kills an average of 15.5 bats per year, adding up to a death toll that could someday threaten populations, according to new research. In Canada’s first comprehensive analysis of wind farm casualties, researchers found that turbines were killing about 47,000 bats per year in 2013. That number will only rise as Canada’s investment in wind energy increases.

“We have about 50 percent more turbines now, so, as of 2016, somewhere around 70,000 bats are being killed in Canada per year,” said Ryan Zimmerling, a wildlife biologist with the Canadian Wildlife Service and first author of a recent study in the Journal of Wildlife Management. “It is possible that those levels of mortality, if they’re not already causing impacts to some species now, could be causing impacts into the future.”

Wind energy companies in Canada are required to monitor bat mortality at newly built wind farms, regularly searching the area under turbines for carcasses. The companies report these data as part of post-construction monitoring, but until now, no one had combined them into a single nation-wide analysis. To see the big picture, Zimmerling and his colleagues analyzed carcass counts from 64 wind farms in nine provinces, using statistical corrections to estimate how many carcasses the surveyors missed.