Impacts of wind energy development on North American bats: A national assessment
Wind energy helps close the gap between energy production and energy consumption; however, it is not entirely environmentally neutral. There are several indirect and direct impacts to birds and bats. The direct impact is primarily mortality by collision with wind turbines. Several cross-site syntheses of bat collision data have resulted in national fatality estimates that vary by more than an order of magnitude (33,000 to 888,000 bats per year). However, no research has taken a national-scale approach to assess spatial, seasonal, and taxonomic variation in bat mortality. We have completed an exhaustive review of the published and unpublished literature on bat collisions with wind turbines and extracted data from over 200 post-construction mortality reports representing 88 U.S. facilities and 11,000 bat fatality records. We are using this database to conduct a national-scale meta-analysis that will address the above research gaps.
Our preliminary analyses illustrate major emergent patterns in bat mortality across the U.S. Among the available data, Hoary Bats (Lasiurus cinereus), Red Bats (Lasiurus borealis), and Silver-haired Bats (Lasionycteris noctivagans) are the species most frequently found killed at U.S. wind turbines. The majority of fatalities occur between late July and early October, with highest counts along forested ridgelines in mountains of the eastern U.S. Ongoing work will address: (1) how sampling biases influence the patterns arising from these raw fatality counts, and (2) whether particular facility and turbine-scale features drive bat mortality rates. Information from these systematic data-driven analyses — the first of their kind to be based on a national data set of this size — will be useful in considering future wind farm sites, designing mortality monitoring protocols, and ultimately, improving our understanding of impacts of wind facilities to bat populations.