Every year, marine experts from around the south-west of England convene, bringing together expertise across species and disciplines to provide a holistic, ecosystem-wide picture of the south-west marine environment. This is part of the annual cycle of the South West Marine Ecosystem programme, or SWME.
The South West Marine Ecosystem (SWME) Programme is an annual, regional programme of communications and reporting on the marine environment in the south west of England.
The South West Marine Ecosystem in 2025
This year, climatic cycles influencing regional sea surface temperatures were linked to shifts in phytoplankton biomass and community structure. Community changes were seen higher up the food web, with herring stocks showing signs of collapse and sardines and anchovies beginning to take their place. A small-sounding change, driving potentially big changes in food webs and fish communities across the South-West. At the other end of the food web, we’re seeing more blue sharks and more bluefin tuna than in previous years. Basking sharks and humpbacks are also appearing in higher abundance off the south-west of England, whereas in Ireland, whale watching businesses were shutting up early as the animals fail to show in their usual numbers.
The common octopus bloom continues; its effects on marine ecosystems and fisheries remain relatively unknown. On a happier note, it’s been a good year for small spiny lobsters.
There are real recovery stories to tell. Seagrass has shown positive signs of recovery over the last decade. On Lundy, seabird populations are rebounding after the removal of the pressure caused by out-of-control rat populations, a reminder that when we remove a threat, nature often does the rest. The ‘South-West Bottlenose Dolphin Consortium’ has officially become the ‘South Coast Bottlenose Dolphin Consortium’, reflecting ecotourism and public efforts that have supported the tracking of a distinct pod of dolphins all the way up to Sussex.
Not every cetacean story is as encouraging. Strandings continue in Cornwall, indicating much larger and unseen mortality due to by-catch. Risso’s dolphin distributions are shifting northwards from the Bay of Biscay, increasing their numbers in our seas but also bringing them into new conflicts with anthropogenic pressures.
Pollution remains a constant. The release of raw sewage into waterways continues to pollute riverine, estuarine and marine ecosystems – a product of wilful underfunding and underregulation. Plastics, referred to as the ‘plan B’ of oil companies, continue to pose a threat to both environmental and human health.
The skies above the water are changing too. There was a noted a shift in seabird patterns, such as Cory’s shearwater, a species that breeds in the Azores, appearing in higher-than-usual numbers along the south-west coast.
Underpinning much of this knowledge is the extraordinary work of volunteers and institutions. A network of more than 300 citizen scientists has contributed seal sightings and photographs, providing valuable information, for example, on pup weaning. New guidance from the MMO is supporting experts in integrating evidence to influence planning decisions, and the Wildlife Trusts have launched the MPA Recovery Assessment tool to help assess and monitor the effectiveness of Marine Protected Areas.
Looking to 2036: predictions on the next ten years for the South West Marine Ecosystem
With last year’s evidence laid out, we turned to forward projections. The Cornwall Wildlife Trust led the SWME audience through an informal horizon scan, drawing on the expertise in the room to paint a picture of what the south-west marine ecosystem might look like in 2036.
- Whilst there was no consensus on whether overall marine biodiversity would increase or decrease, the SWME 2026 cohort predicted that productivity would decrease.
- When asked which species might be thriving in 2036, the common octopus was a popular contender, due perhaps to blooms in recent years. Blue fin tuna, the grey seal, common dolphin, pacific oyster and wakame all got a mention.
- Increases in marine protection were predicted, but despite this cautious optimism, the predicted increase from 10% to 20% of sea area protected would still fall short of 30 x 30 commitments.
- There was a real lack of consensus on whether the seas would be sustainably fished, but a general perception that overall health of the ocean would decline.
- Generally, education and understanding of the ocean by the public were predicted to be on the rise in 2036.
- And the biggest threats facing marine ecosystems in the South-West in 2036? The very same challenges that we face today: climate change, followed by pollution and biological resource use.
Want to know more about the state of the seas in the south-west of England? Look out for the SWME 2025 annual report this summer.