A new study estimates that 18.7 million bats from 28 species died at wind energy sites across the United States between 1981 and 2024. Annual deaths rose from about 100,000 around two decades ago to 1.5 million by 2021. Researchers linked this increase to the growth of wind energy.
Many bats collide with wind turbines, although scientists remain uncertain about why. The machines' noise may attract them, or they may mistake the structures for trees. Bats may also struggle to detect the moving blades.
Deaths can be difficult to count because animals remove bodies and tall grass hides them. Researchers therefore used statistical methods to estimate deaths, accounting for missing information and including wind farms that had not been monitored.
The location and design of turbines affected the risks. Deaths were higher near rivers, which many bats use for food, water and finding their way. Turbines whose blades passed closer to the ground were particularly dangerous, suggesting that better site selection could help.
A separate study examined 141 European wind farms. It found that avoiding turbine operation when local conditions particularly favour bat flight can reduce bat deaths by more than 80 per cent. However, this approach did not reduce deaths among migratory birds, which also collide with turbines.
