Abstract
As the U.S. seeks to increase energy production from renewable energy sources, development of wind power resources continues to grow. One of the most important ecological issues restricting wind energy development, especially the siting of wind turbines, is the potential adverse effect on bats. High levels of bat fatality have been recorded at a number of wind energy facilities, especially in the eastern United States. The U.S. Department of Energy contracted with Versar, Inc., and Exponent to develop a spatially-explicit site screening tool to evaluate the mortality of bats resulting from interactions (collisions or barotrauma) with wind turbines. The resulting Bat Vulnerability Assessment Tool (BVAT) presented in this report integrates spatial information about turbine locations, bat habitat features, and bat behavior as it relates to possible interactions with turbines. A model demonstration was conducted that focuses on two bat species, the eastern red bat (Lasiurus borealis) and the Indiana bat (Myotis sodalis). The eastern red bat is a relatively common tree-roosting species that ranges broadly during migration in the Eastern U.S., whereas the Indiana bat is regional species that migrates between a summer range and cave hibernacula. Moreover, Indiana bats are listed as endangered, and so the impacts to this species are of particular interest. The model demonstration used conditions at the Mountaineer Wind Energy Center (MWEC), which consists of 44 wind turbines arranged in a linear array near Thomas, West Virginia (Tucker County), to illustrate model functions and not to represent actual or potential impacts of the facility. The turbines at MWEC are erected on the ridge of Backbone Mountain with a nacelle height of 70 meters and a collision area of 72 meters (blade height) or 4,071 meters square. The habitat surrounding the turbines is an Appalachian mixed mesophytic forest. Model sensitivity runs showed that bat mortality in the model was most sensitive to perceptual range and flying height. The BVAT model demonstration found that after 30 model iterations, Red bats suffered greater rates of mortality (i.e., 2.5 times the number of bats killed per 10-day period) than Indiana bats, primarily resulting from the higher flying height of the red bat. The model described in this report is a first release. There are opportunities to expand and enhance the model in the future. For example, additional focus on the model experience would include adding project level saving/loading, integrating the outputs (trajectory mapping) into the main output window, and providing tools for preparing habitat maps. In addition to the model framework, the actual modeling options could be enhanced by adding associative learning (including additional behavioral states), adding additional movement models, and exploring the information transfer among bats. Ultimately, this standalone model could be integrated into ArcGIS as a plugin.