What are the largest climate change related threats to marine ecosystems in the Nordic region – views from policy makers and managers

We here map which impacts from climate change policy makers and managers in the environmental sector from Nordic countries consider to be the largest treats for marine ecosystems in the region. This is in fulfilment of NorMECC’s Subgoal 2 (Deliverable 4 and 5). The overview is based upon direct communication with selected policy makers and managers underpinned by additional information from relevant recent marine ecosystem management plans from Nordic countries. We did not conduct a formal survey, and no statistical or other quantitative analysis was conducted. Still, our clear impression is that the opinions given are representative. We consider the findings to be highly relevant towards the main goal of this report and the NorMECC project, i.e., to obtain and make available a good overview of observed and expected impacts of climate change on a wide range of marine species in Nordic waters. While our results should provide guidance towards topics of priority, this should not be taken to imply that pressures not highlighted necessarily are of no importance in the future. Our findings in this part of the report are presented briefly, we do not explain underlying mechanisms or refer to supporting literature.  Such information is provided in the first part of the report and in-depth in the scientific papers referred to there. 

We divide our presentation into two: Important pressures (including very brief comments on effects) and Means to further develop Nordic cooperation.

Climate change related pressures and challenges brought up as especially important are summarised in Table 5 and briefly described afterwards.

Table 5. Climate change related pressures and challenges brought up as especially important

This pressure is brought up by “everyone” and “everywhere” and is undoubtedly considered to be among the most important impacts of climate change on marine species and ecosystems in the Nordic region. Warming is affecting and will further affect all regions, although both mechanisms and consequences differ. For instance, rise in the mean sea surface temperatures have been consistently observed in the Baltic over recent decades. Both surface and deeper water layers are showing warming. Overall, the Baltic Sea is warming faster than the global oceans. In the Norwegian and Barents seas the temperatures have fluctuated, but the warm period ca 2004–2012 had significant ecosystem impact, with expanding distributions of mackerel and cod.

Marine heatwaves are becoming more frequent throughout the Nordic region. In Norwegian waters the greatest concern for these effects is so far in southerly areas, e.g. linked to kelp forests being heavily impacted and reduced since the 1990s. In Norway there have also been warm-water episodes that have been detrimental to salmon farming, both in the south and in the summer of 2024 when salmon lice for the first time became a severe issue far north. Also in the Baltic MHWs now occur more often. In response and preparedness, The Finnish Meteorological Institute (FMI) provide an indicator to track marine heatwaves in the Finnish coastal areas (FMI Ocean Indicator).

The largest overall decrease and most striking pictures are from the high Arctic circumpolarly, including the northern Barents Sea and the area around Svalbard. However, the sea extent, thickness and length of ice season have over recent decades decreased also in the Baltic Sea. The ice winters there are becoming milder, and the probability of severe ice winters has decreased. The average length of the ice winter is projected to shorten 6 days per decade in the Bothnian Bay during this century based on RCP4.5 scenarios. 

In this context Sea level rise (SLR) was pointed to as an issue relevant for the Baltic. It is of course a global problem, but with geographically different magnitude and consequence. The effects of SLR will increase with time, more so in the case of weak greenhouse gas release mitigation. The impacts om marine life will naturally be most pronounced close to shore. The Nordic region is still “recovering” from the last ice age, causing differentiated rates of sea level vs land uplift. The Baltic Sea was covered by more ice than the Oslo area, which in turn had more ice than western Norway. Thus, for instance along the Finnish coast the land uplift still protects the coast from eustatic sea level rise. However, in the future the effects will not be sufficient to fully compensate the sea level rise. On the Gulf of Bothnia coast, the decreasing trend in the relative mean sea level will slow down. Still, from present until 2100 RCP4.5 scenarios show 20 – 30 cm decrease in the relative mean sea level in the Bothnian Bay and 20 – 30 cm increase in the Gulf of Finland. Similarly, the estimated sea level rise for the period from 1986–2005 to 2100 under the RCP4.5 scenario is estimated to be 38 cm in Stavanger on the SW coast of Norway, but 0 in Oslo. 

Although reported to be of concern also in southern Norwegian sea areas and fjord systems, eutrophication “over fertilising” is particularly problematic in the Baltic Sea. Here eutrophication and climate change are often stated to be the worst problems, which in turn exacerbate other phenomena, such as changes in biogeochemistry including oxygen levels. Land-use activities such as agriculture and forestry practices are considered to be the biggest culprits.

Human land-use practices are challenging and will further challenge biodiversity especially coastally. In addition to eutrophication, coastal browning and changes in freshwater runoff (e.g., with more intense rainstorms) were mentioned as important. Profound effects are observed and expected on marine life in, e.g., southern Norwegian sea areas and fjord systems where especially the Oslofjord is impacted by runoff and wastewater from a large catchment area.

Climate change may cause mismatch between phytoplankton, zooplankton and fish production. Effects in this category occur in, e.g., Norwegian waters and could be expected to intensify, following a too heavy burden from cumulative impacts. Mismatch in time between young stages of fish and their zooplankton prey e.g. affect seabird populations through lack of food in critical stages of especially the breeding season, when the populations are confined to search for food in areas reachable from the breeding colonies.

Some effects of climate change on marine species are expected to propagate to industries and society. There are both direct and indirect effects. Fisheries would be expected to be the most heavily affected, due to the dependence on sustainable harvesting from the natural production of wild-living stocks of fish, crustaceans and molluscs. Without measures counteracting ecosystem impacts and stress, and increasing ecosystem resilience and robustness, yields from harvesting may become increasingly uncertain over time.  For example, in Finnish waters fisheries are affected by adverse environmental states and economically less valuable fish increasing in abundance at the cost of other more appreciated species. In Limfjorden, the most productive area for both mussel fishery (bottom) and aquaculture (suspended cultures) in Denmark, major changes are expected. In particular due to decreases in bottom oxygen, wild mussels will suffer – more so under the more severe climate change scenarios. On the other hand, harvest of farmed mussels (in the water column) is expected to increase significantly in all scenarios. The degree of nutrient regulation through a Water Management plan also is of high importance. Tourism and recreational activities like swimming or spending time by the sea is/will likely be negatively affected by algal blooms and other non-pleasing environmental conditions.  Generally, it was pointed to that legislation, permits for activities and more will affect the development.

This section is a follow-up to questions to a panel debate at the final conference of the Nordic Council of Ministers Vision Project Marine Management and Climate in Gothenburg, November 2024.

To enhance the foundation for successful internation cooperation, it is important to establish a platform where all necessary data is accessible to relevant countries, so well-balanced decisions between harvesting and conservation can be made. Furthermore, enhancing public awareness both locally and nationally is significant, so that both threats and solutions to the impacts on the ocean is made clear. It is about getting people aware and involved.

The importance of marine protected areas (MPAs) was highlighted by respondents. It was said that by including MPAs more actively into marine management, one would provide for safeguarding of important ecological functions and resilient ecosystems. When designating MPAs, it is important to account also for the ongoing alterations in the environment and ecosystems due to climate change, ensuring that these MPAs are resilient to anticipated impacts. While the development of MPAs has come quite far in the Nordic region, this latter aspect still seems to be considered only to little degree. There are, however, processes moving in this direction in some countries (Finland was mentioned). In parallel to developing MPAs, one should identify what areas are available to fisheries and other industries – promoting stronger predictability for both the sustained delivery of ecosystem services and the industries’ activity and long-term value creation.

Environmental managers further argued that more coordinated work should be done towards establishing cross-border MPAs in shared Nordic waters. In theory at least, larger, strictly protected areas could enable habitats to be more resilient to climate change. Cross-national MPAs would demand good practices for exchanging relevant information between countries. To enhance this, and in support of well-founded decisions for appointing an MPA, a platform, like that mentioned above, should include all necessary information/data for selection of MPA areas. Further, common management plans for larger cross-border MPAs should be developed.  It was underlined that there already exist international bodies working on conservation planning, like HELCOM in the Baltic. Still, it was suggested that a (new or existing) body could operate on a more holistic and cross-border level and have a larger mandate to make decisions. Ultimately, a network of MPAs could be established in Nordic waters, including MPAs that cross national boundaries where it makes sense in an environment and ecosystem conservation context.

Collaboration between managers and scientists was proposed as an important measure in future ocean management to maintain and improve environmental conditions while facilitating value creation in Nordic marine areas. Such collaboration can enhance the understanding of the challenges there are on both sides. However, from a conservation point of view far stronger measures are likely needed. One respondent stated that (s)he is in favour of “nature first”, implying strict limitation of human activities. We should at least safeguard some sort of “baseline” before even considering economic activities.  Following this reasoning, for something to be sustainably utilised, the resource should first exist on a sustainable level, i.e., conservation comes before economic exploitation, and the exploitation is directed at the “surplus” beyond the sustainable level. Although the respondent sees the need for a reasonable balance, to account for e.g., livelihoods, (s)he argues that with climate change, biodiversity loss, and more the above is additionally important.

The Convention on Biological Diversity emphasized at COP16 the connection between climate (change) and nature (degradation). There should be little doubt that enabling climate change adaptation is highly relevant for nature conservation. Within this complex a relevant question, asked at the Gothenburg conference, is if restoration of ecosystems can help us strengthen marine nature's resilience to climate change.  Our conservation-oriented responded does not disagree but sees restoration as a last resort. Deteriorating ecosystems to the degree of requiring restoration should be avoided, as restoration can be very costly, compared to not deteriorating it in the first place. Moreover, restoring single ecosystem features or ensembles has a limited ability to mitigate climate change (as they are relatively small-scale compared to human activity), and first and foremost human activity should be limited. On a more local level, perhaps a restored habitat may function as a sort of refuge for species, but the benefits will likely be offset by human activities either elsewhere or at least on a larger scale.

However, another respondent sees restoration of ecosystems in a more positive light (the apparent disagreement may be related to scale considered). Following this respondent, restoration could be expected to improve marine nature's resilience against climate change – and to give good long-term results. Giving space and time for processes like natural rewilding would be an important approach in this respect.