Strategies for Mitigating Impacts to Aerofauna from Offshore Wind Energy Development: Available Evidence and Data Gaps

Abstract

Offshore wind energy (OSW) development, while a key strategy for reducing global reliance on fossil fuels, nevertheless has environmental effects that should be mitigated. We reviewed the scientific literature and gray literature to identify approaches for mitigating (e.g., avoiding, minimizing, or compensating for) the effects of OSW development on birds and bats (aerofauna). The review included studies from other industries where relevant, including terrestrial wind energy and the offshore oil and gas industry. Of a total of 212 mitigation approaches from 233 source documents, 59% of proposed approaches were not tested in the reviewed literature to assess effectiveness at mitigating anthropogenic impacts to aerofauna. Of the mitigation approaches that were field tested or implemented, the reviewed literature indicated evidence of their effectiveness in only about 36% of cases. Thus, there was no evidence of effectiveness for 86% of the mitigation approaches identified in this literature review. For birds, minimization approaches related to lighting (e.g., reducing artificial light, avoiding white and steady-burning lights) were the most commonly tested and effective methods for reducing maladaptive attraction and collisions. For bats, minimization via alteration of turbine operations (e.g., curtailment and feathering of turbine blades) were most commonly shown to be effective. Minimization was the main focus of this review but there is limited evidence of effectiveness for most approaches, and we suggest implementation of dedicated testing to explore the effectiveness of commonly suggested and implemented mitigation measures such as curtailment for birds. As such, avoidance of effects (via careful siting of industrial activity and related measures to avoid effects to wildlife and their habitats) remains the best available option for mitigation. To fully mitigate the effects of OSW development on aerofauna, compensation and offset strategies should also be further explored.