Ecological Impact Assessments Don’t Prevent Bat Deaths at Wind Farms

A new study shows that expensive ecological impact assessments aren’t enough to predict risks to bats in proposed wind farms. Inadequate survey methods and unpredictable bat behavior were two contributing factors. The findings are in a paper that was just published in the journal Current Biology.

Wind farms produce electricity through the use of large turbines. Wind power is generally considered a safe, efficient method of power generation and the technique doesn’t result in any air pollution. Turbines can kill bats and birds, however, and ecological impact assessments (EcIAs) are now conducted prior to the construction of a new wind farm. EcIAs are supposed to help prevent bat fatalities by identifying risks and mitigating them with modifications to the farm. These assessments are expensive and time-consuming.

A team of researchers from the University of Exeter analyzed data from EcIAs conducted at 29 wind farms throughout the United Kingdom. In total, 46 wind farms were studied but EcIAs were unavailable for many of them. The team used audio analysis to track bat activity at each site. The researchers also used search dogs to find dead bats, which are tiny and hard to spot in a large wind farm.

The team found that EcIAs were not good predictors of bat activity or fatalities. Bat activity often went up or down after the wind farms became operational, regardless of the results of the original assessment. The assessments also failed to predict bat deaths and the farms deemed safe were still responsible for killing at least one bat per month. The researchers believe part of the problem is the unpredictability of bat behavior. Bats may not initially live in an area but there is some research supporting the idea that they can become attracted to wind turbines. This might occur due to ultrasound emissions or increased availability of prey insects. These deaths may go unnoticed in traditional surveys since the affected bat species are very small.

The findings show that EcIAs may not be the best way to determine the safety of a proposed wind farm. The authors believe that better data collection and survey methods could improve the assessments. They also recommend that wind farms reduce turbine activity at night to decrease the risk to bats.


Lintott et al. Ecological impact assessments fail to reduce risk of bat casualties at wind farms. Current Biology (2016).

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