Understanding Wind Energy Impacts on Bats and Testing Reduction Strategies in South Texas
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Negative impacts from burning fossil fuels, including climate change, are promoting an increase in development of renewable energy alternatives. In response, wind energy development is expanding at an exponential rate across the globe. However, wind energy development has long been known to directly impact bats, which incur fatalities at wind turbines when struck by moving turbine blades. In the U.S., Texas is the leading producer of wind energy with approximately >13,300 commercially operating wind turbines while also having the greatest diversity of bats. Despite this, research in Texas on this topic is lacking with only a few wind energy facilities producing publicly available or peer-reviewed data. In this dissertation, I conducted one of the first comprehensive studies to understand and reduce wind energy impacts on bats in South Texas. My study site was the Los Vientos Wind Energy Facility with 255 wind turbines encompassing 22,666 ha in Starr County, Texas, part of the Lower Rio Grande Valley region. For my first study I estimated bat fatality rates at Los Vientos using a novel fatality estimator and reported a moderate to high fatality rate, in which Brazilian free-tailed bats (Tadarida brasiliensis) were the most impacted species. Based on my results, I recommend bat impact reduction strategies for this location and others in the region experiencing similar impacts. Los Vientos has a similar bat species composition and climate as other regions in the southwestern U.S. and northern Mexico which also lack data on wind energy impacts to bats. My results might provide insights and guidance for these regions as well.
In my second study, I monitored bat acoustic activity at three wind turbines at Los Vientos during late summer to early fall. I investigated relationships between bat activity and bat fatality, weather, and temporal covariates to further our understanding of conditions under which bats are at risk. My results revealed specific climatic (e.g., low wind speeds) and temporal conditions (e.g., hour of the night) during which bats are most active at wind turbines, and showed a positive relationship between activity and fatality, thereby highlighting conditions in which bats are more susceptible to fatality.
In my final study, I tested the efficacy of a novel ultrasonic acoustic deterrent system to reduce bat fatalities at wind turbines. Results of my study indicate this technology is a promising tool for reducing fatalities of Brazilian free-tailed bats and hoary bats (Lasiurus cinereus). This was one of the most successful field trials using acoustic deterrents to date. However, my results indicate species-specific responses to deterrents, particularly for yellow bat spp. Therefore, I conclude the technology warrants further studies to increase effectiveness for more species.
Studies investigating wind energy impacts to bats are timely, relevant, and necessary for conservation of imperiled species, informing policy, and guiding responsible wind energy development. Moreover, developing regional and site-specific impact reduction strategies are important for maximizing the generation of renewable energy. Results of my studies can be used to develop such strategies in other data-deficient regions with similar climates and bat species such as the southwestern U.S. and northern Mexico, and with further improvements, the applications of the acoustic deterrent technology I tested are potentially global in reach.