Consolidating the State of Knowledge: A Synoptical Review of Wind Energy's Wildlife Effects.

Wind energy development contributes substantially to achieve climate protection goals. Unintended side effects, especially on wildlife, have long been discussed and substantial research has evolved over the last decade. At this stage, it is important to identify what we have learnt so far, as well as which predominant uncertainties and gaps remain. This review article aims to consolidate the state of knowledge, providing a qualitative analysis of the main effects of wind energy development on- and offshore, focusing on frequently studied species groups (bats, breeding and resting birds, raptors, migratory birds, marine mammals). We reviewed over 220 publications from which we identified predominant hypotheses that were summarized and displayed in tables. Journal publications, conference contributions, and further studies have been considered. We found that research focusing on offshore wind energy within the last couple of years has increased significantly as well, catching up with the vast amount of onshore studies. Some hypotheses have been verified by numerous publications and a consensus has been reached (e.g., correlation between bat activity and weather factors), while others are still being debated more (e.g., determination of migratory corridors) or remain unknown (e.g., effect on population level). Factors influencing potential effects were mainly related to species characteristics (morphology, phenology, abundance, behavior, and response to turbines) or site characteristics (landscape features, weather, and habitat quality). Consolidating the state of research provides the groundwork for the identification of mitigation measures and advanced planning approaches. However, the quantification of effects remains challenging and uncertainties will always persist.

Cautious but committed: moving toward adaptive planning and operation strategies for renewable energy's wildlife implications.

Wildlife planning for renewable energy must cope with the uncertainties of potential wildlife impacts. Unfortunately, the environmental policies which instigate renewable energy and those which protect wildlife are not coherently aligned-creating a green versus green dilemma. Thus, climate mitigation efforts trigger renewable energy development, but then face substantial barriers from biodiversity protection instruments and practices. This article briefly reviews wind energy and wildlife interactions, highlighting the lively debated effects on bats. Today, planning and siting of renewable energy are guided by the precautionary principle in an attempt to carefully address wildlife challenges. However, this planning attitude creates limitations as it struggles to negotiate the aforementioned green versus green dilemma. More adaptive planning and management strategies and practices hold the potential to reconcile these discrepancies to some degree. This adaptive approach is discussed using facets of case studies from policy, planning, siting, and operational stages of wind energy in Germany and the United States, with one case showing adaptive planning in action for solar energy as well. This article attempts to highlight the benefits of more adaptive approaches as well as the possible shortcomings, such as reduced planning security for renewable energy developers. In conclusion, these studies show that adaptive planning and operation strategies can be designed to supplement and enhance the precautionary principle in wildlife planning for green energy.