Wind farms may kill more bats than estimated

Wind farms have a long documented history of killing hundreds of thousands of birds and bats each year. As it turns out, the bat toll may be higher than previously estimated.

In a study published Monday, researchers in the United Kingdom found that environmental impact assessments — the main tool used to predict the ecological effects of a new energy development — commonly failed to predict the number of bats that would have fatal collisions with wind turbines’ spinning blades.

Even in the few cases where researchers said early assessments accurately predicted the danger to bats, efforts to mitigate those risks often did not succeed.

“The findings highlight the difficulty of establishing with certainty the effect of major developments before they occur,” co-author Fiona Mathews said. The results were published in the journal Cell Press.

Mathews, a mammalian biologist at the University of Exeter, and several colleagues surveyed 46 wind farms across the U.K. over the course of a month to estimate bat fatalities, relying heavily on search dogs to locate fallen bats.

They then compared their findings from each site to the environmental assessments they were able to access. In most cases, the pre-construction assessments had not accurately predicted the risk of bat fatalities. And even where companies had put in place mitigation measures to try to steer bats clear of the turbines, the researchers found that bats were still killed.

“Bat activity recording during pre-construction surveys may not accurately reflect activity postconstruction,” the authors wrote. “This may be due to bats changing their behaviour at turbines, as bats may be attracted to wind farm sites for a variety of reasons, including the emission of ultrasound from turbines and increased prey availability.”