Bird collision assessments are generally made at the scale of a single wind farm. While especially in offshore situations such assessments already hold several assumptions, even bigger challenges exist on estimating the cumulative impact of multiple wind farms and the impacts at population level. In this paper, the number of collision victims at Belgian offshore wind farms was estimated with a (theoretical) collision risk model based on technical turbine specifications, bird-related parameters and bird density data of both local seabirds and passerine migrants. Bird density data were gathered by visual censuses and radar registrations. The outcome of the model was extrapolated to future development scenarios in the Belgian part of the North Sea and in the entire North Sea, and then further used for a preliminary assessment of the impact at population level for the species at risk. The results indicate that the cumulative impact of a realistic scenario of 10,000 turbines in the North Sea might have a significant negative effect at population level for lesser and great black-backed gull. We further show that during a single night of intense songbird migration, the number of collision victims among passerine migrants might be in the order of magnitude of several thousands in the entire North Sea. We argue that it is of great importance to further develop methods to quantify the uncertainties and to minimise the assumptions, in order to assure more reliable cumulative impact assessments.
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The authors acknowledge C-Power and Belwind for their willing cooperation throughout the research. The crew of the RV Belgica, RV Zeeleeuw and RV Simon Stevin are thanked for their enthusiasm and technical support throughout the sampling campaigns. Lieven Naudts from the Royal Belgian Institute of Natural Sciences (RBINS) and André Cattrijsse & Michiel Tjampens from the Flanders Marine Institute (VLIZ) are especially thanked for their invaluable logistic support. Ship time on RV Belgica was provided by the Belgian Science Policy (BELSPO) and Royal Belgian Institute of Natural Sciences, Operational Directorate Natural Environment. Ship time on the RV Zeeleeuw and RV Simon Stevin was provided by DAB Vloot and the Flanders Marine Institute (VLIZ).
Finally, we wish to thank all colleagues and volunteers who assisted in the seabird counts, especially to Wouter Courtens, Hilbran Verstraete, Marc Van de walle & Walter Wackenier.
R. Brabant and N. Vanermen shared first authorship
Guest editors: Steven Degraer, Jennifer Dannheim, Andrew B. Gill, Han Lindeboom & Dan Wilhelmsson/Environmental impacts of offshore wind farms
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Brabant, R., Vanermen, N., Stienen, E.W.M. et al. Towards a cumulative collision risk assessment of local and migrating birds in North Sea offshore wind farms. Hydrobiologia 756, 63–74 (2015). https://doi.org/10.1007/s10750-015-2224-2
- Offshore wind farms
- Bird collisions
- Bird migration
- Collision risk modelling
- Impact assessment