The management utility of large-scale environmental drivers of bat mortality at wind energy facilities: The effects of facility size, elevation and geographic location

Abstract

Wind power development can cause direct mortality of both birds and bats through collisions with turbines, but the estimates of mortality necessary to evaluate the impact of this mortality are unavailable for many facilities and regions. We used monitoring surveys from the majority of facilities in a contiguous region spanning 800 km of southwest-northeast distance and almost 900 m of elevation (Quebec, Canada) to produce estimates of mortality per facility. The distribution of these estimated mortalities is skewed low with more than two thirds of facilities having annual mortalities of less than 50 individuals. We then used this set of estimated annual mortalities to explore how changes in installed capacity (megawatts), elevation and geographic position affected estimated annual mortality, with the goal of providing guidance to conservation mangers attempting to find strategies for minimizing mortality. More installed capacity (MW) correlated with higher mortality, but installed capacity alone was a poor predictor of estimated mortality. Medium-sized facilities were the best management strategy to minimize per MW mortality. Mortality decreased with increasing elevation and decreased from southwest to northeast within this region. The cumulative effects of this mortality have the potential to be devastating for bats, particularly migratory species, which account for the majority of carcasses observed. Our results also highlight the necessity of monitoring at all facilities in order to identify the small number of high mortality facilities for effective application of mitigation measures.