Short Science Summary: Bat Interactions with Land-Based Wind Energy: A European and North American Perspective

Wind turbine-related fatalities of bats were first observed over 40 years ago, but it was not until the early 2000s when unexpectedly high numbers of fatality events were discovered at wind energy facilities in the eastern U.S. that the impacts of wind turbines on bats became a concern. Fatality rates vary dramatically and can range from zero to more than 100 bats/turbine/year at individual wind energy facilities. However, certain patterns are evident across the northern hemisphere. For example, fatalities are most frequent during late summer and autumn and are often concentrated during nights with warm temperatures and low wind speeds. Understanding these patterns helped in developing the first strategies to reduce fatality by altering turbine operations during the timing and conditions bats were most vulnerable.

Estimates of fatality indicate hundreds of thousands of bats are killed annually at wind turbines both in Europe and North America. Given bats are longlived and typically only have 1 to 2 pups per year, existing fatality rates may not be sustainable for certain species. Recent studies indicate population-level declines are possible, particularly given the anticipated growth of wind energy development. However, demographic and population data are limited for most bat species, making it difficult to determine population sizes and trends. In the European Union, all bats are protected under the Habitats Directive and several species are on the IUCN Red List of threatened species. In contrast, only a few species are afforded legal protection in North America under either the United States’ Endangered Species Act or Canada’s Species at Risk Act.