Wind turbines are large machines that use wind to make electricity. A new study estimates that 18.7 million bats from 28 different kinds died at US wind farms between 1981 and 2024. About 100,000 died each year around twenty years ago. As wind energy grew, this number reached 1.5 million in 2021.
Many bats hit the machines, but scientists do not know exactly why. The sound may bring bats closer, or bats may think the machines are trees. They may also have trouble noticing the moving parts.
Counting dead bats is difficult. Animals may take their bodies away, and tall grass may hide them. Researchers used maths to estimate deaths, including at wind farms without checks.
Wind farms near rivers had more bat deaths, and machines with moving parts closer to the ground were especially dangerous. Many bats use rivers to find food, water and their way around. Choosing different places for wind farms could reduce deaths.
Another study looked at 141 European wind farms. It found that stopping the machines when local conditions are especially good for bats to fly can cut bat deaths by more than 80 per cent. However, this approach did not reduce deaths among birds that travel with the seasons.
