Date Published: May 14, 2019
Publisher: Public Library of Science
Author(s): Benjamin D. Best, Patrick N. Halpin, Bi-Song Yue.
Although offshore wind energy development (OWED) offers a much-needed renewable energy alternative to fossil fuels, holistic and effective methods for evaluating environmental impacts on wildlife in both space and time have been lacking. The lengthy environmental compliance process, estimated to incur a 7–10 year permitting timeline , has been identified as a significant impediment to offshore energy development in U.S. waters. During operation, seabirds can collide and be displaced by turbines. During episodic pre-operation phases, cetaceans are most heavily impacted acoustically by pile driving (and similarly seismic air gun surveys for oil and gas exploration). The varying nature of impacts in space and time leads us to conclude that sites should be selected in space to minimize long-term operational impacts on seabirds, and timing of surveying and construction activities to be conducted in times of the year when sensitive migratory marine mammals are least present. We developed a novel spatiotemporal decision support framework that interactively visualizes tradeoffs between OWED industry profits and wildlife sensitivities, in both space and time. The framework highlights sites on a map that are the most profitable and least sensitive to seabirds. Within the U.S. Mid-Atlantic study area, the New York Call Areas are particularly well optimized for minimal impact on seabirds with maximal profits to OWED. For a given site, pre-operational activities (e.g. pile driving and seismic air gun surveying) are advised by cetacean sensitivity across months of the year that minimize impacts on migratory cetaceans, particularly those of highest conservation concern such as the North Atlantic right whale (Eubalaena Glacialis). For instance, within optimal sites for the New York Call Area the least impacting months are May and June. Other taxa are certainly affected by OWED and should be incorporated into this framework, but data on their distributions and/or sensitivities is currently less well known. Built with open-source software made publicly available, the authors hope this framework will be extended even more comprehensively into the future as our knowledge on species distributions and OWED sensitivities expands for streamlining environmental compliance.
As of the end of 2017, the total installed offshore wind capacity is at 18,814 megawatts (MW) worldwide with the United Kingdom leading and Germany following at 6,836 MW and 5,355 MW respectively . Europe accounts for 84% of installed capacity with most of the remainder in Asia. The United States presently has just one grid connected production facility in Block Island, RI with a 30 MW capacity. However as of June 2018, the U.S. does have a total project pipeline of 25,434 MW (3,892 MW of project-specific capacity and 21,542 MW of undeveloped lease area potential capacity), according the U.S. Department of Energy. Although other projects are slated for the future, what accounts for this stark lack of development in U.S. waters?
To realize the general concept of the spatiotemporal framework (Fig 1) three components must be analyzed and brought together (Fig 2): 1) offshore wind energy profitability over space, 2) seabird sensitivity over space, and 3) cetacean sensitivity over space and time. Profitability to the wind industry is estimated as a function of transmission distance and wind availability. Seabird distributions get aggregated into a single cumulative sensitivity map with weightings based on sensitivity to offshore wind turbines. Each site (i.e. pixel on the map) can then be plotted in variable space as a tradeoff between wind profitability versus bird sensitivity. Each of these sites can be assigned a new utility value as a function of each axes, i.e. maximizing wind profitability while minimizing bird sensitivity. This new utility value can then be mapped out in space. Cetacean distributions are also aggregated into a cumulative sensitivity map, except weights are by extinction risk and a map is made for each month to capture variability in migratory patterns that could be differentially affected by episodic pile driving. These general processes (Fig 2) are given more in-depth treatment throughout the rest of the methods.
The recommended framework for prospecting offshore wind energy development is to consider areas that maximize profitability to offshore wind energy while minimizing to sensitivity to bird, since birds are exposed over the long-term operational phase of wind farms. Mapping the utility, which is described by the tradeoff plot, highlights sites that most efficiently meet both objectives. Subsequent planning for construction activities should be timed so as to minimize acoustic exposure to cetaceans of conservation concern. This too can be systematically quantified with a cetacean sensitivity plot per site over time (Figs 1 & 2).