Impacts of Climate Change on the European Marine and Coastal Environment:
Although all ecosystems have been influenced by many other factors, such as eutrophication and overfishing, every sea in Europe has shown already at least some changes which are most likely direct or indirect result of recent climate change. Although there can be no certainty regarding the precise nature and rate of future climate change, even the more moderate of the predicted scenarios is expected to further alter the marine environment.
For the most northern seas, such as the Arctic and the Barents Sea, the most obvious temperature-related change is the decline in sea-ice cover. Both the Arctic and the Barents Sea are predicted to be ice-free during summer within the next 100 years. The reduction of the formerly ice-covered area is expected to result in a decline, and possible extinction, of the species that depend on this habitat, such as ringed seals and polar bears. The disappearance of the ice may increase local productivity level in the sea. At a larger scale, the reduction of the ice-covered areas may lead to an increase in heat absorption and changes in convection and water mass formation, possibly affecting temperature and ocean currents globally.
The population of many marine species are exhibiting a displacement northward. For most open seas, there is evidence of species moving northwards and/or northern species being replaced by more southern ones. It is expected that within open systems there will generally be northward movement of species, for example Arctic species will be replaced by Atlantic species in the more northern seas such as the Arctic, Barents Sea and the Nordic Seas, while temperate species will be replaced by more subtropical species in the southern seas such as the Iberian upwelling margin.
The rate and direction of this movement, however, differs amongst the various seas and species. Enclosed seas, such as the Baltic Sea, the Mediterranean and the Black Sea, have only small and primarily east-west orientated movement corridors, which may restrict northward displacement in these areas. Further warming will presumably drive the marine species with a preference for cooler waters up to the northern coastlines of these areas, followed by extinction if they are not able to adapt to the new circumstances.
Noticeably, the enclosed seas appear to have undergone far more dramatic changes than the more open seas during the past decades. Relatively small changes in the frequency of inflow (as in the Baltic Sea) or in temperature (as in the Eastern Mediterranean and Black Sea) have had strong effects on large parts of the ecosystem. This implies that although the temperature increase is predicted to be relatively small in the more southern waters, the effects of climate change are still likely to be quite large in these waters.
For seas that are highly influenced by river runoff, such as the Baltic Sea, an increase in freshwater due to enhanced rainfall will lead to a shift from marine to more brackish and even freshwater species. If enclosed systems such as the Mediterranean and the Black Sea lose their endemic species, their associated niches will probably be filled by species originating from adjacent waters and, possibly, from other sources such as ballast water.
Such changes not only affect the local ecosystems, but also the international fishing industry when commercial species are affected. It must be noted, however, that a climate-induced decline in species abundance and biodiversity may trigger over-fishing if one tries to gain the same yield from a (locally) reduced stock. Under such circumstances, it is impossible to distinguish between the effects of climate change and over-fishing.
European seas consist of more than 68,000 kilometres of coastline, harbouring internationally important wetlands, and major cities and ports. The combination of accelerating sea level rise and a possible increase in the frequency and intensity of storms, as predicted for most European seas, will severely increase the risk of flooding and subsequent loss of these areas. Further extension, raising and reinforcement of artificial coastal defences may protect populated areas, but result in loss of sedimentary nourishment of coastal marine habitats, with consequences for living marine resources, including aquaculture.
For future planning and development of adaptation strategies to climate change, improved understanding and prevision of the ultimate consequences of climate change in relation to concurrent effects of other stressors such as changes in nutrient loads, invasion of non-indigenous species and exploitation of marine living resources is needed.
Reference: Catharina J.M. Philippart, et. al, Climate Change on the European Marine and Coastal Environment. Marine Board – ESF Position Paper. Strassbourg.