The increasing global deployment of wind energy has given rise to concerns about potential adverse effects on certain wildlife species and habitats. The United States and European nations use environmental impact assessments (EIAs) to evaluate the environmental effects of wind energy and inform wind energy planning, siting, and operational processes. A key component of the EIA is the cumulative effects analysis/assessment (CEA). CEAs consider the effects of a proposed development in the context of past, present, and future developments, as well as other (non-wind) activities. However, practitioners worldwide have struggled to implement costeffective and consistent processes for CEAs. Further, there is no widely accepted scientific methodology to assess cumulative effects. As wind energy deployment continues to expand, developing a consistent and scientifically based approach to CEAs may provide greater comparability across assessments and more cost-effective mitigation options during siting, operations, and decommissioning/repowering, while minimizing regulatory hurdles.
The current research highlights the need to develop recommended practices and consistent terminology, collect and disseminate baseline data, and integrate regional and project-level analyses to streamline CEAs. The challenges described in this report affect costs and timelines for wind energy deployment, and the current conclusions from CEAs may not accurately capture the real cumulative impact on species and ecosystems. In addition, there is a growing need for confidence in CEA analysis. Pursuing further research and updating current practices to align with the current recommended practices provide opportunities to address these challenges.