Cornwall’s marine environment is facing a critical moment as new data reveals that the UK seas have reached the warmest temperatures since records began. This alarming milestone, driven by climate change, is already impacting the delicate ecosystems off our coast, with cascading effects on marine species and habitats that Cornwall Wildlife Trust is closely monitoring. 

The latest scientific reports confirm record warmth this year, following high sea temperatures in both 2023 and 2024, with marine heatwave conditions altering the seas around Cornwall. Such warming disrupts the balance of marine life, from plankton to top predators, threatening the health of our coastal waters and the communities that rely on them. 

Cornwall’s seas are already experiencing the effects of warming waters. Species once common around Cornwall’s coast, such as basking sharks, are now shifting their range northwards or deeper to find cooler refuges. While the full impact of changes in the distribution and behaviour of species can’t yet be fully understood or predicted, we do know  there will be new pressures on native species and habitats that have evolved to thrive in more temperate conditions, with the possibility of altered breeding cycles and reduced fish stocks. 

One striking example of the dynamic marine life around Cornwall is the remarkable return of the Atlantic bluefin tuna. Once thought lost from UK waters for over 60 years, this apex predator has made a notable comeback thanks to international conservation efforts and improved fisheries management. Bluefin tuna sightings have surged, with Cornwall becoming a key migratory stop on their path from the Mediterranean and Bay of Biscay. Their presence signals the potential for recovery of marine ecosystems but also highlights the delicate balance needed to sustain these gains amid changing ocean conditions.

The recovery of bluefin tuna underlines the power of targeted conservation, but warming seas pose new challenges. Changes in prey availability and habitat quality require ongoing vigilance and adaptive management to safeguard species and ecosystems.  

Other impacts felt this year, further signs of changing waters, include unusual sightings such as a leatherback turtle off St Austell Bay and two orcas off the Isles of Scilly, a massive boom in octopus numbers in southwest waters, and huge aggregations of spider crabs gathering to moult. 

One vital tool in the management and protection of our seas is the establishment and enforcement of Marine Protected Areas (MPAs). MPAs safeguard important habitats and species by limiting harmful activities such as overfishing and seabed disturbance. They help ecosystems build resilience against climate impacts by providing safe havens where wildlife can recover and thrive.

Cornwall Wildlife Trust actively supports expanding and properly managing MPAs around our coast, urging policymakers to strengthen these vital marine reserves. You can add your support by emailing the Marine Management Organisation (MMO), who are running the consultation, and Minister Hardy via this link.  

Tell the MMO and Minister Hardy that you support the ban of bottom trawling in seabed Marine Protected Areas

While the news of record ocean warming is sobering, it also underscores the urgency and importance of our work. The seas around Cornwall are living laboratories where the effects of climate change and conservation efforts play out in real time. Through collaboration, science, and community commitment, we remain dedicated to a future where marine ecosystems not only survive but thrive.

There are many ways that you can support our work and commitment to the health of the ocean. You can donate directly to our Ocean Emergency Fund, which supports our marine initiatives. You can volunteer your time and participate in things like citizen science and coastal clean-ups, or you can add use your voice and join us in advocating for marine protection. Every action counts in addressing the pressures from climate change, pollution, and unsustainable fisheries. 

The ocean’s rising temperatures remind us that nature’s resilience has limits. It is our collective responsibility to reduce carbon emissions, protect critical habitats, and adopt sustainable practices. Cornwall Wildlife Trust remains steadfast in our mission to create a Cornwall where nature thrives, to safeguard our unique marine wildlife, ensuring that future generations inherit healthy seas rich with life.