Climate-driven trophic cascades affecting seabirds around the British Isles

After flourishing during the second half of the twentieth century, many North Sea seabird populations are now in decline. Much evidence is accumulating that climate change is driving these negative trends in growth rate. Climate-driven changes in the physical environment may affect seabirds both directly and indirectly. Direct impacts such as increasingly common extreme weather events will result in negative physiological responses. However, climate effects on seabirds are more likely to be indirect and mediated by prey quality and availability. Mounting evidence suggests that climate impacts on lower trophic levels are altering the pathway of energy to seabirds. While the basis for changes in primary production are complex and uncertain, climate-driven changes in the availability of sandeels (primarily Ammodytes marinus) and the copepod Calanus finmarchicus, key prey species in adjacent trophic levels, appear to be causing a reduction in breeding success and growth rate in several British seabird species.