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Synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America

We conclude that increasing cut-in speed between 1.5 and 3.0 m/s or feathering blades and slowing rotor speed up to the turbine manufacturer’s cut-in speed yields substantial reductions in fatality of bats. Given the magnitude and extent of bat fatalities worldwide, the conservation implications of our findings are critically important. Research efforts should continue to focus on incorporating additional variables, in addition to wind speed (e.g., temperature, time of night, bat activity) into treatments and explore using automated systems to maximize wind production while still minimizing bat fatalities. Although additional studies are needed to optimize operational mitigation, we believe increasing cut-in speeds to the levels tested in these studies (generally 1.5–3.0 m/s) offers an ecologically sound and economically feasible strategy for reducing bat fatalities at wind energy facilities and should be implemented broadly.

Edward B. Arnett
Theodore Roosevelt Conservation Partnership
Gregory D. Johnson
Wally P. Erickson
Western EcoSystems Technology
Cris D. Hein
Bat Conservation International

Prepared for the National Renewable Energy Laboratory, March 2013

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