Climate change

The North-East Atlantic has already experienced physical, chemical and biological effects linked to climate change, including changes in sea temperature, sea ice coverage and sea and oxygen levels, a decline in primary productivity in the North Sea in the past 25 years, and shifts in fish distribution. Further impacts due to a changing climate can be expected in the future, which will differ in different areas of the North-East Atlantic. In addition, actions to reduce greenhouse gas emissions, notably a major expansion of offshore renewable energy, will have consequences for the marine environment. (More details in the Climate Change Thematic Assessment )

Human activities affecting the marine environment of the North-East Atlantic are now being influenced by climate change and will continue to be affected in the next decade and beyond. Adaptation and resilience building will be needed in relation to negative impacts; in some cases, there could be positive impacts for activities. Measures to reduce greenhouse gas emissions will also affect activities. Potential influences on activities include:

• fisheries. Stock distributions and/or sizes may change, for example through increased catch potential in high latitude areas (although impacts on commercially important stocks are uncertain) and decreases further south. There may be increasing complexity and contention in assessment, allocation, and transboundary management of catches. Fishers may need to adapt fishing practices (e.g., to address changes in the frequency of extreme events, or to ensure resilience of fish stocks);
• aquaculture. Possible negative impacts include loss of production or infrastructure due to increased intensity or frequency of extreme events (such as storms or heatwaves); an increase in diseases, toxic and / or harmful algal blooms and parasites; decreased productivity due to temperature rise; effects on production of oyster spat or mussel seed; or the effect of ocean acidification on shellfish. However, there is some possibility of positive impacts such as higher growth rates in some warm-water finfish or shellfish aquaculture;
• aggregates extraction. Sea-level rise due to climate change could increase demand for sand for coastal reinforcement and maintenance. In the Netherlands, the most recent expectation is for 10-37 million m3 of sand per year in the period after 2035, depending on a sea level rise of 2-8 mm per year;
• agriculture. Changes to rainfall patterns and impacts due to extreme rainfall events will impact hydrological connectivity and mobilisation of nutrients and other contaminants (including microplastics) from agricultural land to surface waters and in turn marine waters;
• waste water. More intense rainfall can overload sewer networks, leading to surface water flooding and overflow at urban waste water treatment plants, with untreated sewage flowing into rivers, lakes, or coastal areas;
• shipping. Reduced ice coverage in Arctic Waters could lead to further increases in shipping activity in some parts of that Region. How significant this will be remains uncertain, depending on factors such as the length of the Arctic shipping season and the economic viability of trans-Arctic routes;
• tourism. Factors such as changes in rainfall, extreme weather events, sea level rise, and beach erosion could affect this activity.

Future priorities for OSPAR

The NEAES 2030 includes an objective to carry out climate change impact assessments on the OSPAR Maritime Area and its uses in 2023 and every six years thereafter (NEAES 2030 S10.O3). These assessments should review how climate change is affecting the human activities covered by this thematic assessment, and how they are adapting.

Ocean acidification

Ocean acidification is a perturbation of the physicochemical environment of the world’s oceans that changes the acidity of the water (pH) (see:  OSPAR’s Ocean Acidification Other Assessment for details). It is a multi-stressor of organisms, meaning it impacts organisms in multiple ways and at multiple stages of their development, and the impacts coincide with other environmental changes (for example temperature change). It can also lead to the dissolution of exposed calcareous structures that are often essential in shaping benthic habitats harbouring protected species. Although protected and endangered species are more vulnerable to environmental change, ocean acidification impacts all organisms and also those of commercial interest: it is expected that standing stocks of commercial species may be significantly reduced under the influence of ocean acidification. Case studies in OSPAR’s ocean acidification assessment suggest that ocean acidification may hamper the ability of Atlantic cod populations (Gadus morhua) to deal with changing water temperatures due to climate change and that bivalve larvae are especially vulnerable to shell dissolution due to ocean acidification, with potential ramifications for commercial bivalve cultivation.