Offshore wind energy development has progressed worldwide since 1991, and it is expected to play a substantial role in the reduction in greenhouse gas emissions, due to 1) the scale at which current technologies can be deployed, and 2) proximity of deployment sites to coastal population centers. However, with limited data on wildlife impacts from offshore wind, or on the relative impacts of offshore wind vs. other types of energy infrastructure, it is difficult for developers, regulators, and the general public to appropriately weigh these potential advantages against expected environmental impacts. There is a particular paucity of data for many North American species of management concern, including baleen whales and sea turtles. We review the existing data on collision mortality, behavioral effects such as attraction and avoidance, and habitat-related impacts to wildlife from offshore wind energy development. In the context of the United States regulatory framework for offshore wind, we also discuss ongoing efforts to assess baseline patterns of marine populations, predict potential effects, and minimize impacts to wildlife during development activities.
Collision mortality is seldom observed at offshore wind turbines. In part this may be due to technological limitations in detecting collision mortalities in the marine environment, but the available data suggest that behavioral effects are much more common. Some species of birds, fish, and pinnipeds have shown evidence of attraction to operational wind turbines, while other species have shown substantial avoidance behaviors during construction activities and, in some cases, during operations as well. In particular, displacement of animals from pre-existing habitat use areas may be a concern if it occurs over long temporal scales. Acoustic impacts to marine mammals and other taxa, particularly during construction activities, has been a topic of extensive concern, but there are still substantial gaps in our knowledge in this area. Available information suggests that the scope and degree of wildlife impacts may vary in relation to a number of environmental, facility-specific, and species-specific factors, as well as individual characteristics such as age and life history stage. We review the available information on these topics, provide several examples of decision making for offshore wind energy development in the face of uncertainty, and suggest specific areas of research to facilitate future decisions.