Warming UK seas could fundamentally reshape marine ecosystems, study finds

A four‑year investigation has warned that rising temperatures in waters around the United Kingdom and the broader north‑east Atlantic may destabilise marine food webs, weaken ocean health and threaten food security by 2050, according to scientists who released the findings in Science Advances.

The researchers identified the seas surrounding the British and Irish islands – especially the southern North Sea – as one of twenty global “marine climate hotspots” that have warmed the quickest over the past half‑century.

Under a scenario of 3 °C (5.4 °F) warming by the end of the century, the team projected that fish and seabed invertebrates could become more diverse by mid‑century, while key plankton groups lower in the food chain are likely to lose species, creating a predator‑prey imbalance that could reshape ecosystems.

“What surprised us is that warming doesn’t increase or decrease biodiversity across the board,” said Elena Couce, a marine ecologist at the Centre for Environment, Fisheries and Aquaculture Science (Cefas) and co‑lead author of the report.

She added that “while some groups higher up the food chain, like fish, may gain species in parts of the north‑east Atlantic, key plankton groups that underpin marine ecosystems are projected to lose species.”

The study was led by Cefas and involved an international consortium that included the University of East Anglia, the Marine Biological Association, UiT the Arctic University of Norway, the Royal Netherlands Institute for Sea Research and the Technical University of Denmark.

Couce explained that as temperatures rise, “all the species from the equator are going to move north and south. The UK is in the middle latitudes, so we expected diversity to go up, because you get species from the south that are more diverse than the species you lose to the north.”

Earlier Cefas work on principal fish species had suggested that warming in north‑west European waters would create climate “winners” such as anchovies, seabass and sardines, while “losers” like Atlantic cod, haddock and coley would fare worse.

The new analysis, which covered UK waters and the wider north‑east Atlantic including Ireland and France, estimated that by mid‑century fish and seabed invertebrate diversity could rise by roughly 12 %, whereas phytoplankton and zooplankton diversity might fall by about 3 % and 7 % respectively by 2050.

Lily Greig, another Cefas marine ecologist who co‑led the study, warned that “if predator diversity rises while prey diversity falls, that has the potential to disrupt the food chain.” She said the results show climate change could unevenly reshuffle marine biodiversity, meaning gains for some groups do not automatically make the whole ecosystem more resilient.

By pinpointing the fastest‑changing biodiversity hotspots and the most vulnerable parts of the ecosystem, the researchers said their work could act as an early‑warning system for future changes and has already been forwarded to the government’s review of marine protected areas, which is examining fisheries management measures.

Couce told policymakers that “they have a mandate to try to preserve or even increase biodiversity. What we are trying to tell them is climate change is already changing biodiversity, and you need to take that into account before you can make other management plans.”

The team used several long‑term data sets together with advanced machine‑learning techniques to model the link between biodiversity and environmental shifts, enabling predictions of climate‑driven biodiversity change out to 2100.