Using foraging range and colony size to assess the vulnerability of breeding seabirds to oil across regions lacking at-sea distribution data

With the projected increases in shipping activity and hydrocarbon extraction globally, there is an increased risk of negative ecological impacts from oil pollution on the marine environment, including seabirds. Oil Vulnerability Indices (OVIs) are a common approach to assess seabird species vulnerability to oil pollution and to identify where species are most at risk, typically across regional spatial scales and for a relatively limited number of species. This approach generally requires comprehensive data on at-sea distributions and densities; however, for many regions, these data are limited. We present a simplified OVI to assess seabird species vulnerability to oil pollution. To create the spatial component of the OVI, we used a predictive foraging radius approach, using existing colony size and foraging range data, to project at-sea distributions of seabird populations during the breeding season. We demonstrate this approach over a large spatial scale, the eastern North Atlantic, which includes areas where seabird at-sea data are lacking. Our results reveal areas off west Greenland, Iceland, and Norway where seabirds are most vulnerable to oil pollution during the breeding season, largely driven by large colonies of auks (Alcidae). We also identify locations along the coast of mainland Norway, Iceland, and Scotland, where seabirds are particularly at risk to oil pollution associated with major shipping routes. Identifying areas where species are most at risk can help inform where, and which, measures should be put in place to mitigate the impacts of oil pollution, such as protecting and avoiding high risk areas, for example, through adopting dynamic Areas to be Avoided (ATBAs). Our simplified OVI combined with the predictive foraging radius approach can be adapted to other regions globally that lack seabird-at-sea distribution data, to other marine wildlife, and to assess risk from hydrocarbon extraction and other anthropogenic threats, including fishing activities and offshore renewable developments.