Wildlife mortality at wind turbines

Background/Question/Methods Worldwide, wind power development proliferated over the past decade, causing wildlife fatalities mostly due to collisions with wind turbine blades but also due to grading for access roads and tower pads. Comparing wildlife mortality among wind projects can inform of relative and cumulative impacts and can facilitate the formulation of mitigation measures, but comparisons have been hampered by pseudoreplication caused by project differences in wind turbine size and model, landscape, and in monitoring and analytical methodology. Standardizing assumptions, adjustments for undetected fatalities, and the fatality rate metric, I estimated and compared fatality rates among wind turbine models in the Altamont Pass Wind Resource Area (WRA) and among other WRAs for which data were available in reports. My objectives were to compare fatality rates using common methods, test hypotheses of causal factors where possible, and compare pre-construction predictions of fatalities to post-construction estimates.

Results/Conclusions

Fatality rates in the Altamont Pass WRA were inversely proportional to wind turbine size for most species, but they increased with increasing turbine size for bats. Re-analyzing data from other WRAs, my estimates of fatality rates often differed from those reported by the authors of original reports, and I found that post-construction estimates of fatality rates often exceeded pre-construction predictions. Some WRAs caused surprisingly high fatality rates, including one that compared to fatality rates estimated in the Altamont Pass WRA. High inter-annual variation in fatality rates in the Altamont Pass WRA revealed most monitoring programs at other WRA to be too brief. Sources of uncertainty and bias in adjustments for undetected fatalities remain inadequately understood and only crudely addressed in fatality rate estimates, and too few have been subject to independent peer review.