Wind power is helping reshape America’s energy grid, but a new accounting reveals a devastating cost for bats: an estimated 18.7 million animals died after colliding with turbines in the United States between 1981 and 2024. The toll has accelerated alongside the growth of wind farms, reaching more than 1.5 million deaths per year from 2021 onward. The newly published estimate is the broadest assessment yet of turbine-related bat mortality in the country.
Researchers built the estimate from 499 post-construction monitoring reports covering wind facilities in the contiguous 48 states. Their statistical analysis focused on 10 bat species and accounted for differences in search methods, turbine characteristics, and local environmental conditions—factors that can otherwise make one wind farm’s fatality figures difficult to compare with another’s. The resulting total is not a literal body count, but a national estimate assembled from many incomplete surveys.
The losses fall particularly heavily on migratory, tree-roosting bats. The hoary bat, eastern red bat, and silver-haired bat are consistently identified as the species most vulnerable to turbine collisions, together representing roughly 70% to 80% of reported North American wind-facility fatalities, according to the National Park Service. These bats travel through the same airspace occupied by turbine blades, especially during late-summer and autumn migration.
Wind turbines are not the only pressure facing U.S. bats. Habitat loss, disease, climate change, and other human-caused disturbances are already affecting populations, which makes an added source of mortality more consequential than the raw number suggests. The federal government says collisions occur most often during periods when bats are migrating and mating, while some species may also be attracted to turbines or the insects concentrated around them.
The encouraging news is that operators have a practical way to reduce the danger: temporarily slowing or stopping turbines during low-wind periods when bats are most active. A 2024 analysis of a decade of North American studies found that raising the wind speed at which turbines begin operating reduced bat deaths; a 5.0-meter-per-second cutoff was associated with an average reduction of 62%. That approach can reduce wildlife harm while preserving much of a facility’s electricity production, though the new national estimate underscores the scale at which such measures may need to be deployed.
The immediate challenge is balancing faster clean-energy development with safeguards for species that cannot easily absorb additional losses. Better monitoring, seasonal forecasting, acoustic detection, and targeted curtailment could help operators identify the riskiest nights and locations. For fans of these nocturnal insect hunters—and for an energy industry eager to keep its environmental promise—the study turns an often-invisible problem into a number that is difficult to ignore.
