Bats represent a substantial contribution to mammalian species diversity and ecosystem processes in North America, including their role in performing important economic service functions. The development and expansion of wind energy facilities is a key threat to bat populations in North America. Dead bats are being found underneath wind turbines across North America, and bat fatalities have been documented at almost all of the wind facilities at which thorough bat surveys have been conducted. The results suggest that thousands of bats may be killed annually at some wind facilities, and recent estimates suggest that hundreds of thousands of bats may be killed annually in the contiguous United States. Here, I use published bat fatality information to derive estimates of the number of bats killed at wind energy facilities in the contiguous United States in 2012 and conclude that over 600,000 bats may have died as a result of interactions with wind turbines.
Because of their small size and nocturnal habits, it is difficult to estimate the population sizes of bat species over large scales, such as that of the contiguous United States (O’Shea et al. 2003, 2004). As a result, we do not have high-quality estimates of population sizes of most North American bat species; in many cases, bat researchers would not be able to reliably estimate population sizes within an order of magnitude. This lack of reliable population estimates makes conservation and management planning challenging, especially in the face of other recently emerged threats to North American bat populations, such as diseases (e.g., white-nose syndrome; Frick et al. 2010) and a changing climate (such as in arid Western landscapes; Adams 2010). Furthermore, even under the best circumstances, temperate zone insectivorous bats usually exhibit very slow population growth rates because of the tendency of many bat species to give birth to one pup per year and high mortality rates during a bat’s first year of life (O’Shea et al. 2004, Hallam and Federico 2009).
Unlike other threats to bat populations, such as disease and climate change, the impacts of wind energy development are predictable: Bats will be killed when both bats and turbines are active and when they are in close proximity to each other. Given bats’ contribution to mammalian species diversity in North America and their ecological and economic importance, it will be helpful to continue research on the current and future impacts of wind energy development on bat populations. It will also be helpful to support efforts to estimate and monitor bat population sizes throughout North America.