USGS study estimates 18.7 million bats killed at US wind energy facilities

The US Geological Survey said a new study estimated that 18.7 million bats were killed at U.S. onshore wind energy facilities between 1981-2024. The estimate covered onshore facilities in the United States and showed fatalities were more substantial than previously understood.

Researchers analyzed data from close to 500 post-construction monitoring reports at 277 wind energy facilities across the U.S. They used statistical models to estimate when, where and how many bats of ten species were likely to have died at facilities over the past four decades.

Nationwide predictions of fatalities exceeded 1.5 million total fatalities per year starting in 2021. Four species accounted for most fatalities. The study estimated approximately 6.7 million hoory bats, 5.8 million eastern red bats and 3.4 million silver-haired bats were killed across all years.

The three species were migratory, tree-roosting bats and were not the cave-hibernating species most heavily affected by white-nose syndrome. The authors said the findings could broaden the scope and severity of conservation threats to bats.

Researchers found that turbines with a larger rotor-swept area, lower ground clearance and closer proximity to rivers were associated with increased site-level bat fatalities for multiple species. They also examined how turbine size and location related to fatality rates and how risk for each species could vary geographically with environmental factors.

The study supports stopping turbines when bats are more likely to be present, constructing facilities in areas of lower risk and analyzing finer-resolution monitoring data on when fatalities occur. The USGS said these findings can inform natural resource management decisions intended to prevent future bat losses.