Photo of Jeremy Bishop
Warming seas around the UK and the wider north-east Atlantic could reshuffle marine biodiversity unevenly across the food web, with gains among fish masking losses in the plankton that underpin them. That is the central finding of a four-year study led by Cefas and published in Science Advances, which projects climate-driven biodiversity change across four groups of marine life to 2100.
The research brought together Cefas, 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. Using long-term survey data and machine-learning models, the team projected change in phytoplankton, zooplankton, seabed invertebrates and fish, the first systematic assessment of its kind across all four groups in the region, according to the paper.
Predators up, prey down
As reported by The Guardian, the projections suggest that by mid-century fish and seabed invertebrate diversity could increase by about 12%, while phytoplankton and zooplankton diversity could fall by about 3% and 7% respectively by 2050. The authors warn that this imbalance could disrupt food webs and weaken the resilience of ocean ecosystems.
The result runs against a common assumption that biodiversity in mid-latitudes such as the UK would simply rise as species move north from warmer waters. “What surprised us is that warming doesn’t increase or decrease biodiversity across the board,” Cefas marine ecologist and co-lead author Elena Couce told The Guardian. “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.”
Co-lead author Lily Greig, also of Cefas, set out the risk. “If predator diversity rises while prey diversity falls, that has the potential to disrupt the food chain,” she said. “Our results show that climate change could reshuffle marine biodiversity unevenly across the food web, and that gains in some groups do not necessarily mean the ecosystem as a whole is becoming more resilient.”
A hotspot on the UK’s doorstep
The findings land in waters already changing fast. The seas around the British and Irish Isles, particularly the southern North Sea, have previously been identified by Cefas as marine climate hotspots, among the fastest-warming areas globally over the past 50 years. Earlier Cefas work on fish species suggested anchovies, seabass and sardines could be climate winners, with Atlantic cod, haddock and coley among the losers. In July, an MCCIP review of plankton similarly warned that climate change is making the UK’s marine food web less efficient.
Implications for marine protection
The researchers see the work as an early warning system that can show where biodiversity is changing fastest and which parts of the ecosystem are most at risk. It has already been submitted to the government’s review of marine protected areas.
“Policymakers have a mandate to try to preserve or even increase biodiversity,” Couce said. “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.”