Responses of Marine Top Predators to an Offshore Wind Farm in UK Waters: Does Evidence Exist for Displacement?

The number of offshore wind farms is rapidly increasing as they constitute a significant component of global renewable energy strategies. Deployment of the technology within UK waters contributes a significant, and growing,... [ view full abstract ]

The number of offshore wind farms is rapidly increasing as they constitute a significant component of global renewable energy strategies. Deployment of the technology within UK waters contributes a significant, and growing, component of the UK renewable energy generation. There are currently over 3 GW in the UK permitting system, 13.5 GW awaiting construction and 6 GW either under construction or operational. This has given the UK legislators the opportunity to impose post permit-award monitoring requirements upon Developers aimed at providing scientific evidence to the degree of impact experienced by the marine ecological receptors from offshore wind deployment.
A key concern expressed during the permitting phase of a project is displacement of marine top predators from important habitat during offshore wind farm construction and operation. We present the first cross-taxon evidence for no significant long-term displacement from a UK offshore wind farm for two broadly-distributed species of conservation concern : common murre (Uria aalge) and harbour porpoise (Phocoena phocoena). Data were collected during boat-based line transect surveys across a 360 km2 study area that included the Robin Rigg offshore wind farm in UK Waters. Surveys were conducted over ten years across the pre-construction, construction and operational phases of the development. We estimated changes in common murre and harbour porpoise abundance and distribution in response to offshore wind farm construction and operation using generalised mixed models to test for evidence of displacement. Both common murre and harbour porpoise were present across the study area throughout all three development phases, providing evidence for no wide-scale displacement during construction and operation. Results will be presented that indicate there was a significant reduction in harbour porpoise within the Robin Rigg offshore wind farm during construction, but numbers returned to pre-construction levels during operation. Common murre abundance remained similar across all development phases.
Both common murre and harbour porpoise showed significant, local scale density distribution changes across the survey area that appeared to be independent of the presence of the offshore wind farm. Over the same 10 year period of surveys described above, benthos and fish surveys were also undertaken to monitor changes occurring in the highly mobile, estuarine environment in which the Robin Rigg offshore wind farm is located. The results of these surveys suggest that storm and tide related sediment movement, that is unrelated to offshore wind farm presence, is responsible for changes in prey species distribution. Thus our results indicate that local prey availability is likely to be more important in determining the abundance and distribution of marine top predators than perturbations associated with offshore wind farm construction and operation.
These results will be presented and discussed within the context of the developing understanding of potential displacement effect being observed from European offshore wind farms.