Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts

Abstract
Warming of the oceans is evident globally and having significant and sustained impacts on marine ecosystems. Top predators are vulnerable to bottom up effects of climate change operating through lower trophic levels and from a suite of other anthropogenic pressures. However, the cumulative effects of multiple stressors are poorly understood with assessments generally focusing on the impacts of single stressors on single species. Evaluating the vulnerability of multi-species populations to multiple anthropogenic threats is a vital step in understanding current threats and providing a robust baseline against which to assess future changes and target conservation effort. Here we focus on a marine bird community (45 species; 10 families) utilising the Forth and Tay region of the North Sea, UK for breeding, overwintering or migration between 1980 and 2011. Sea surface temperatures (SST) increased significantly in this region, with concomitant changes in marine communities. This area is subject to considerable fishing pressure and disturbance from shipping, and is a priority area for renewable energy developments. We used colony based and at-sea data to quantitatively assess relationships between SST and abundance and demography for 24 species. A qualitative approach using published population trends, climate relationships and foraging sensitivity was undertaken for remaining species. Species with significant negative relationships between counts or demography and SST, or high foraging sensitivity for qualitative assessments, were considered to have high climate vulnerability. Trends in counts and demography were combined with climate vulnerability to give an index of population concern to future climate warming. In total, 53% of species had high vulnerability to climate with 22% species of very high concern (declining trends and high vulnerability to climate) and 22% of high concern (stable trends and high vulnerability to climate). Breeding species (61% high or very high population concern; n=18) and auks, cormorants, grebes, skuas and terns (≥50%) were considered highest risk groups to future climate change. Qualitative assessment of vulnerability to anthropogenic threats (fisheries, pollutants, disturbance and marine renewables) in addition to climate vulnerability found that 96% of species were vulnerable (all breeding and 93% overwintering), with 44% vulnerable to ≥4 threats. The majority of birds in this area of the North Sea face an uncertain future because of simultaneous threats from climate warming and other anthropogenic stressors, potentially threatening the integrity of this important marine bird community.
Year
2014
Category
Refereed journal