How many bats are killed by wind turbines? Study warns of ‘shocking’ increase amid clean energy boom
Researchers warn the death toll of bats has spiralled since the boom in wind energy – but there are solutions at hand.
Wind energy is heralded as a key element in the shift away from fossil fuels, but fresh research reveals a "shocking" number of bats killed annually by spinning turbines in the United States. According to the most extensive study on the subject, 18.7 million bats from 28 species have been killed by wind energy facilities since 1981. In 2021 alone, 1.5 million bats succumbed to wind turbines.
The study published in the Proceedings of the National Academy of Sciences found that the death toll jumped dramatically in recent years, rising from 100,000 bats per year in the early 2000s to the current figure. The reasons behind this increase remain unclear, but researchers have several theories. One hypothesis is that bats are drawn to turbines due to the noise, or they mistake the structures for trees. Another possibility is that bats struggle to detect the blades or are lured by them for other reasons.
The research team points out that most bat mortality studies are based on surveys conducted by wind farm operators, which may not provide a comprehensive picture. Factors like scavenging animals removing carcasses or tall grass concealing dead bats could lead to underestimations. To address this issue, the authors developed a statistical method that accounted for missing data and estimated the number of bats killed across the country, including at unmonitored wind farms.
Despite using advanced statistical techniques, the data's quality remained a limitation, the study acknowledges. The researchers suggest that adjusting the placement of wind facilities could help reduce bat fatalities. For instance, wind farms near rivers tend to have higher mortality rates, as many bat species depend on rivers for food, water, and navigation. Additionally, turbine characteristics play a role, with those having less ground clearance posing a greater threat to bats.
A separate study published in Applied Ecology this month examined 141 wind farms in Europe, where bats are protected under the EU Habitats Directive. The findings suggest that avoiding turbine operation during favorable conditions for bat flight could cut mortalities by more than 80%. Some countries, like Germany, have already mandated mitigation measures since around 2010, including risk assessments during site selection and restrictions during high-risk periods, such as migration seasons or adverse weather conditions.
However, these measures have not proven effective in reducing bat deaths among migratory bird species, which also perish in wind turbine collisions.
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