Taller wind turbines may generally kill more bats and swallows, but species matter.
Renewable energy sources such as wind energy are critical to reduce our reliance on fossil fuels and slow the rate of climate change.
Bats and birds sometimes collide with turbine blades and understanding factors causing wildlife collisions with turbines can help conserve biodiversity while generating essential, renewable energy.
A previous study identified turbine height as a risk factor for wildlife collisions, but turbine height has increased significantly since that analysis.
Read this open access paper on the FACETS website.
Since 2006, the height of wind turbines has increased from approximately 120 to 170 m in Canada.
Our study aimed to test whether this trend represented a greater collision risk for wildlife, or not. To test whether turbine height affects the number of bats and swallows killed by turbines, we used a dataset from 811 wind turbines in Ontario, Canada.
We found that taller turbines were associated with more fatalities for three bat species, Big Brown Bat, Hoary Bat, and Silver-Haired Bat, but fewer fatalities for Little Brown Bats and Eastern Red Bats.
Fatalities of Purple Martins and Tree Swallows also were higher at taller turbines than shorter turbines, but fatalities of Cliff Swallows and Barn Swallows were not associated with turbine height.
Fatalities of bats and swallows increased with turbine height for some species, but not all. Therefore, increasing turbine height represents an increased risk of collision for only a subset of affected species.
Species differences such as flight altitude and relative abundance (the number of individuals flying around) may contribute to differences in fatalities at turbines.
Because population estimates and flight altitudes of swallows are better understood than those of bats, we speculate that swallow fatalities may provide clues about aspects of bat ecology that are not well understood, such as flight altitudes.
Although we found a relationship between turbine height and fatalities for some species, a recent study found that the number of animals killed at a turbine depends on the amount of energy the turbine produces.
Therefore, although larger turbines that produce more energy may kill more animals than smaller turbines that produce less energy, the number of fatalities per amount of energy produced may remain the same.
Because of this, proven methods to reduce fatalities for bats, such as preventing turbine blades from spinning when wind speeds are low, may be a more effective tool for bat conservation than regulating turbine size.
Read the paper — Effects of turbine height and cut-in speed on bat and swallow fatalities at wind energy facilities by Alexandra M. Anderson, Catherine B. Jardine, J.R. Zimmerling, Erin F. Baerwald, and Christina M. Davy.
