Many species of plankton and fish have shifted their distribution northward and sub‑tropical species are occurring with increasing frequency in European waters, changing the composition of local and regional marine ecosystems in a major way (2). Recent studies have shown that the northward movement of southerly species has caused species richness in the North Sea to increase (3). This may have negative ecological and socio‑economic effects: the three large species that have decreased their range the most in the North Sea are all commercially relevant, while only one of the five most increasing species and less than half of the all the species that expanded their range are of commercial value. A climate change-induced shift from large to smaller species is thus likely to reduce the value of North Sea fisheries (3).
During the past 40 years there has been a northerly movement of warmer‑water plankton by 10° latitude (1100 km) in the north‑east Atlantic and a similar retreat of colder‑water plankton to the north. This northerly movement has continued over the past few years and appears to have accelerated since 2000. Sole and other warm‑water species have become relatively more abundant in northerly areas, while plaice and other cold‑water species have become rare in southerly areas (6). Climate is only one of many factors which affect distribution and abundance, but the consistency of the response of this particular index to temperature, both within particular areas (i.e. time trend) and across all areas (i.e. geographic trend) suggest that the causal relationship is quite strong. Scenario projections of future movements of marine species have not yet been made (4).
The kinds of fish which are available for human consumption are not necessarily affected by the distribution changes shown above, because fish are often transported long distances from where they are caught to where they are marketed, but the prices of fish may change if certain species that are common today become less common. People eating locally caught fish may notice changes in the species they catch or buy. Changes in distribution may affect the management of fisheries. Fisheries regulations in the EU include allocations of quotas based on historic catch patterns, and these may need to be revised (4). In general it is not possible to predict whether northward shifts in distribution will have a positive or a negative effect on total fisheries production (5).
In Denmark, it is expected that there will be a need to restructure fish and shellfish cultivation in both fresh and salt water (1).
More run-off in the entire Baltic region could make the surface layers in the inner Danish waters less saline. In combination with changed wind conditions and increased run-off of nutrients, this could present a risk of negative consequences for marine ecosystems and commercial fish stocks in the form of oxygen depletion (7).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Denmark.
- Danish Government (2008)
- Brander et al. (2003); Beare et al. (2004); Beare et al. (2005); Perry et al. (2005); Stebbing et al. (2002), in: EEA, JRC and WHO (2008)
- Hiddink and Hofstede (2008), in: EEA, JRC and WHO (2008)
- EEA, JRC and WHO (2008)
- Brander (2007), in: EEA, JRC and WHO (2008)
- Brander et al., 2003, in: EEA, JRC and WHO (2008)
- Danish Ministry of Climate and Energy (2010)