(The majority of the report is in Norwegian. However, there is an abstract in English.)
In 2010 NINA performed a screening of areas that may be suitable for the establishment of offshore wind power plants (Christensen-Dals gaard et al. 2010). The surveyed area ranged from the Swedish border in the south (North Sea/Skagerrak) to the northern tip of Andøya (Norwegian Sea). Following the publishing of the report the Directorate for Nature management wanted to extend the analysis so that it also covered the Barents Sea (National scale). While the 2010-report also included potential effects on white-tailed eagles, Eurasian eagle owl and waders, this geographically extended analysis only covers seabirds.
Marine wind farms are a relatively new element in European waters, and at present there have been few investigations carried out to study their short- and long-term environmental effects. While there have been several studies to identify environmental impacts of wind farms in other countries, there is currently only one such study in Norway, on the island of Smøla. So far, four mechanisms have been emphasized with regard to the impact of wind farms on birds: 1) mortality resulting from collisions with wind turbines (tower and wings ), 2) avoidance due to interference from installations in operation and from the activity associated with the construction of wind farms; 3) loss and change of habitat, through habitat degradation and fragmentation, and 4) barrier effects, which may increase the flight distance and increase the birds' energy demands.
In this report, we have chosen to use a methodology that was developed to evaluate seabird vulnerability to marine wind farms in German waters. This method provides a species-specific vulnerability index (SSI) based on nine factors: flight maneuverability, flight altitude, percentage of time flying, nocturnal flight activity, sensitivity towards disturbance by ship/helicopter traffic, flexibility in habitat use, biogeographical population size, adult survival rate and conservation status. In addition we added a 10’th factor in this analysis; the regional proportions of the national populations of each species involved. Combined with a measure of density or relative proportion of the relevant species in an area, a wind farm sensitivity index (WSI) is created. The WSI can be summed for all species found in the area at different times of the year to give a total WSI for seabirds. The existing data for seabirds in winter and in the breeding season was of sufficient quality to be used for this method.
While working with the update of the screening on a National scale we realized that the scope were much more challenging than anticipated. The Norwegian coastline, spanning 13 degrees of latitude, is extremely variable with respect to sea temperatures, sea currents, topography, seabird habitats and the distribution of seabird species (e.g. Barrett et al. 2006; Forsgren et al. 2009). The Barents Sea is known for its large numbers of especially auks, whereas the seabird fauna in the south is dominated by smaller colonies of gulls (Barrett et al. 2006). In order to avoid that the large numbers of seabirds in north completely masked the smaller numbers in south we decided to perform a regional analysis of seabird vulnerability, with the North Sea, the Norwegian Sea and the Barents Sea as the regions analyzed.
The results are presented in maps, where the WSI is given for 10x10 km squares. The results demonstrate a clear difference in vulnerability between the regions and the seasons (overwintering, breeding). Compared with the previous analysis (Christensen-Dalsgaard et al. 2010) the present, regional assessment, caused more areas to be defined as vulnerable. Among the areas that were defined as vulnerable in the current analysis many were breeding areas along the Helgeland coast that were defined as important in earlier work (e.g. Systad et al. 2007, Christensen-Dalsgaard et al. 2008). In the North Sea more areas were identified as vulnerable in the wintering season indicating that the regional assessment caused a more correct reflection of vulnerable areas in the North- and the Norwegian Seas. For the Barents Sea the regional assessment caused many areas to display as apparently less important than areas in south- and mid-Norway. This is because the proportional number of a seabird species in an area was compared with the total regional population of that species. Thus, the large numbers of seabirds in the Barents Sea were reduced to relative numbers and, consequently, a loss of a small number of birds in an area with few birds were on the same footing as a loss of a large number of birds in an area with a large number of birds. An assessment of the importance and the consequences of potential loss of seabirds in different areas due to wind power plants is a challenge for the environmental governments. From a biological point of view this is not a satisfactorily way to assess potential effects and consequences. Therefore, the author’s point of view is that it is pertinent to do regional assessments of vulnerability in order to pinpoint important populations and areas on a smaller scale. The current assessment is not, however, intended to replace an assessment on a national scale where also the dispersion and migration of birds is included. Large scale assessments of the effects of given factors will always be imprinted with uncertainties, simply due to the large scale.
In the North Sea the same areas that were identified as vulnerable in relation to marine wind farms in Christensen-Dalsgaard et al. (2010) were also identified as vulnerable in the present analysis. The regional analysis, however, implied a higher level of vulnerability in the northern areas during the breeding season. This was caused by the extending of the buffer zone from the Runde into the North Sea. Thus, the great numbers of auks at Runde influenced the vulnerability assessments in the North Sea were the numbers of auks are small. Also the (small) colonies of auks at Einevarden, Klovningen and Veststeinen got a higher vulnerability score in the North Sea region in the present assessment. For the overwintering period the coast of Vestfold got a higher vulnerability score due to the presence of marine ducks, and the Østfold and Jæren and Boknafjord area got a higher score due to the presence of Great cormorants and Shags.
For the Norwegian Sea there were quite big discrepancies between the previous analysis (Christensen-Dalsgaard et al. 2010) and the present one. This was especially pronounced along the Helgeland coast due to the large numbers of breeding great cormorants and Shags. In addition, the seabird colony at Røst got a lower vulnerability score in the present analysis, probably due to the increased vulnerability in other areas.
The Barents Sea area was not treated in Christensen-Dalsgaard et al. (2010). From a general knowledge of the occurrence of seabirds in the area it is clear that the regional division of the Norwegian coast give very different results compared to what a national assessment would have done. On a national scale the large number of seabirds in the Barents Sea would have masked many of the important areas in southern Norway.
For seabirds at sea the results from the present analysis is comparable with those in Christensen-Dalsgaard et al. (2010).
In our study, the analysis of vulnerability is done for separate areas in relation to the presence of birds. However, in the case of extensive development of large numbers of wind farms in close proximity to one another, different and stronger responses can be expected from both individuals and populations of birds than what has until now been documented for smaller offshore wind power plants. During the future development of wind power plants, both off- and on shore, it will be important to not only consider each wind power plant in isolation, but to focus on what their total or cumulative environmental effects will be.
It should be noted that our analysis is for guidance only. It is suitable for large-scale evaluations of the vulnerability of areas. To assess the suitability of specific areas for the development of wind power plants, it is, in addition to this report, necessary to study local occurrences of birds and identify important functional areas for seabirds. The basis for the index should also be assessed and reviewed continuously, so that the latest knowledge about the effects of wind farms can be incorporated in later analysis.
Norwegian Title: Offshore vindenergianlegg og sjøfugl. Oppdatert screening av potensielle konfliktområder på nasjonal skala