Developing projections of change for conservation and management in the Southern Ocean

Climate change will alter the structure and functioning of Southern Ocean ecosystems, affect the ecosystem services they provide, and therefore require development of appropriate strategies for conservation and fisheries management. Here we report the outcomes of studies of the potential impacts of climate change on Antarctic krill in the Scotia Sea and Antarctic Peninsula region; the centre of the current krill fishery (Area 48). We considered the processes influencing population dynamics and local availability of krill in the region and how these will be affected by future change. We examined available projections of physical, chemical and ecological change, highlighting uncertainty in model projections. Simple uni-directional responses to change are unlikely across the whole region. Under a high emissions scenario, future warming and loss of sea ice is expected to result in a reduction in the abundance and biomass of krill in northern areas of the Scotia Sea, with consequent southward shifts in the distribution of the various krill-dependent species. These changes are also likely to have major impacts on the structure of the food web, which may occur rapidly as particular biological thresholds are reached. The recovery of cetacean populations will also generate simultaneous changes. Under lower emission scenarios impacts on krill populations and the ecosystem would be reduced. Uncertainty in both future climate-driven physical change and in the susceptibility of krill populations in Area 48 to change needs to be incorporated into projections in order to generate a range of feasible outcomes. Communicating such uncertainty, and hence risks associated with different management and conservation strategies, is crucial in the provision of advice to policy makers. We emphasize the importance of a systematic approach to improve scenarios and ecosystem models, and to develop quantified model projections of ecosystem change to inform conservation and management decisions.