With wind energy growing as an alternative resource to curb the rate of climate change, conservationists raise concern regarding the number of turbines that are built within the flight path of bats. To learn more about the widespread amount of turbine-related bat dealths, researchers have for the first time tracked down the animals' origin using what they call chemical fingerprints.
"We knew which species were being killed, but we didn't know how they were moving across the landscape, how many were out there, or what their genetic diversity was," said study co-author David Nelson, an associate professor from the University of Maryland Center for Environmental Science's Appalachian Laboratory. "Our research is helping conservation managers to understand, 'Are these species that we need to be concerned about?'"
Wind turbines built along forested ridgelines of the Appalachian Mountains have some of the highest bat mortality rates in the world. The two most common species killed in turbine accidents in North America are the hoary bat (Lasiurus cinereus) and the eastern red bat (Lasiurus borealis).
However, little is actually known about North American bat migration routes or how wind-energy development may impact them. Using stable isotope and genetic analysis, researchers were able to accurately assess the impacts of wind-energy development on bats living in the Appalachian region.
"Understanding the potential impacts of turbine-associated bat deaths is often complicated by a lack of data,"Cortney Pylant, lead author of the study, added. "Studies such as this can help to identify species and populations at particular risk."
Researchers determined the summering grounds of bats killed by wind turbines using a type of chemical fingerprint known as stable hydrogen isotopes. Different forms of hydrogen exist in water depending on where it falls. Therefore, hydrogen isotope signatures found in the bats' hair reveal where they had traveled. For instance, rain from higher elevations or close to the coast has a different signature than rain from lower elevations or further inland.
DNA was also extracted from the bats' wing tissue and examined to assess how the animals would fare when adapting to increased mortality among their population. Analyzing the bats' genes also gave researchers a better idea of how many individuals of a species remain in the breeding population, which in turn can be used to determine whether or not the population is viable.
Overall, researchers found half of red bats killed in the area were not local residents and probably summered at locations far from the wind turbines, while almost all of the hoary bats summered nearby. Furthermore, researchers concluded the red bats represented a single, massive breeding population in the hundreds of thousands to millions of individuals, while the hoary bats represented a relatively small population, with a breeding group of only a couple thousand to tens of thousands of individuals.
This, researchers say, suggests that red bats may fare better than local hoary bats when either population suffers wind turbine-related deaths.
As primary predators of night-flying insects, bats reduce the spread of insect-borne plant and animal pathogens and prevent large amounts of crop damage each year. Therefore, the study has vast implications for conservation of bat populations and wind-energy development.
Their findings were recently published in the journal Ecological Applications.