Rising Bat Deaths from Wind Turbines Raise Concerns
Wind energy is seen as a fundamental pillar in the transition from fossil fuels, but new research warns that spinning turbines kill a shocking number of bats each year.
According to the largest study to date, 18.7 million bats from 28 different species have died at wind energy sites across the U.S. from 1981 to 2024.
The study, published in the Proceedings of the National Academy of Sciences, found that about two decades ago, 100,000 bats died annually. By 2021, this number had risen to 1.5 million bats per year, linked to the boom in wind energy.
Why Bat Deaths May Have Been Underestimated for Years
Many bats collide with turbines, but scientists are still unsure why this happens. One hypothesis is that they are attracted to the noise, or they mistake these structures for trees.
Researchers also note that bats may have difficulty detecting the blades or may be attracted to them for other reasons.
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Most mortality studies are based on searches conducted by wind farm operators, which may not provide a complete picture, as methods can vary and leave room for underestimating the scale of the problem.
For example, scavengers may quickly remove carcasses, and tall grass can hide remains.
Therefore, the authors developed a statistical approach that accounted for missing data and allowed for estimating how many bats of each species could have been killed nationwide.
“Despite using modern statistical methods, the state of the data remained a limiting factor in our analysis,” the study states.
How Can Bat Deaths Be Reduced?
The authors argue that changing the placement of wind energy sites could reduce the risk of bat fatalities. Wind farms located near rivers tend to record higher mortality, as many bat species rely on rivers for food, water, and navigation.
Characteristics of the wind turbines themselves are also important. The team warns that turbines with shorter distances from the ground to the blades are particularly dangerous.
Another study published in Applied Ecology this month examined 141 wind farms in Europe, where bat species are protected under the EU Habitats Directive.
The authors found that shutting down turbines when local conditions are “particularly favorable” for bat flight could reduce mortality by more than 80 percent.
In some countries, such as Germany, mitigation measures have been in place since 2010. These typically include risk assessments at the site selection stage and operational restrictions, such as prohibiting rotor rotation during high-risk periods, like migration seasons or under weather conditions when bats are most active.
However, this strategy has not reduced the number of migratory birds that also fall victim to spinning turbines.
