Greater North Sea ecoregion - Ecosystem Overview

Key Signals

Human activities and their pressures

· Fishing continues to be the main threat to ecosystem health. This is despite a decrease in fishing pressure in recent decades as can be observed from two of its main pressures, i.e. species extraction and physical seabed disturbance. A further reduction in fishing pressure is likely to improve the status of the majority of the ecosystem components.

· Across the ecoregion, the depth zone 0-200m is the most impacted by bottom fishing pressure. On average (including areas not trawled), the seabed in this depth zone was trawled 1.7 times in 2022. When evaluated at the c-square scale (0.05x 0.05 degrees), 70% of grid cells in the 0-200m zone are at least partly trawled dropping to 27% in the 200-800m depth zone.

· Shipping is responsible for the majority (53%) of the introductions of non-indigenous-species, mainly through ballast water and hull fouling, and has clearly increased over the past two decades. Aquaculture is the next most important activity, responsible for a further 18% of introductions. Effects of this pressure may include: the out-competing of native species, the fouling of aquaculture and fishing gear, and fish kills through toxin production.

· Energy production activities such as oil and gas extraction industries are still among the main activities impacting the ecosystem through pressures like contaminants and physical habitat loss. Pressures from oil and gas industries are expected to decrease, while pressures caused by offshore windfarms are expected to increase with the ongoing energy transition.

State of the ecosystem

· Sensitivity of seabed habitats is highest in the northeastern North Sea and Kattegat and lowest in the southern North Sea. The southern North Sea is less sensitive mainly because of the high natural disturbance.

· Offshore mud is mainly affected by Nephrops fisheries and has experienced the highest fishing pressure and impact compared to other habitats.

· The stock sizes of most groups of commercial species are now overall above levels that can provide the maximum sustainable yield (MSY); however, some individual species within these groups may still be below MSY levels.

· The abundance of many seabirds is declining; reasons for this include changes in migration patterns, an outbreak of highly pathogenic avian flu, and reductions in breeding success

· The numbers of two main seal species in the ecoregion – grey seal (Halichoerus grypus) and harbour seal (Phoca vitulina) – have increased from an all-time low in the 1970s, with large population changes over the past decades caused by two major outbreaks of the phocine distemper virus. Trends in the abundance of cetaceans are less known.

Climate change

· Climate change is causing the warming of surface water temperature. This has already changed the spatial distribution of several plankton and fish species within the ecoregion and is likely to continue. Further cascading effects are likely to occur throughout the ecosystem with consequences on the spatial distribution of fisheries. Marine spatial planning should therefore consider this when planning infrastructure such as wind farms or implementing marine protected areas.

Environmental and socio-economic context

· Eutrophication was impacting the ecoregion in previous decades, peaking in the 1980s; however, the introduction of measures to reduce riverine input of nutrients since then has reduced this pressure to the point of no major concern.

· The current trend of increased fuel prices and resulting decreased fishing with bottom‑towed gears is likely to result in a further reduction of the extraction of demersal fish and disturbance of seabed habitats. If this also results in a shift toward less fuel‑intensive fisheries, such as gillnets, than this is likely to result in increased bycatch risk of seabirds and marine mammals, including longer-term effects from lost and abandoned fishing gear.

· In targeting specific fisheries with additional management interventions, it is worth considering that small-scale coastal fisheries contribute 10% of value landed but have regional importance in terms of employment (18% full‑time equivalent [FTE]) and revenue (11%).