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Scientists embark on world-first study to reveal carbon stored in UK seas

UK governments urged to protect blue carbon in marine habitats which is critical for tackling climate change 

Marine habitats are at risk of releasing carbon when damaged by bottom trawling as well as sea and coastal development

The UK will become the first nation to produce a complete map of its blue carbon stores, thanks to a new, pioneering project.  

The Blue Carbon Mapping project – led by the Scottish Association for Marine Science (SAMS) and funded by WWF-UK in collaboration with The Wildlife Trusts and RSPB – builds on the blue carbon mapping that began in Scotland.  

The final report will be produced by the summer of 2023, with initial findings expected later this year.  

There is currently limited information about how much carbon is stored in and sequestered by UK marine habitats such as saltmarsh, seagrass beds, kelp forest, biogenic reefs, and marine sediments.  

The project aims to address this scientific blind spot, paving the way for better understanding and protection of the UK’s blue carbon habitats. Scientists will assess the carbon storage and sequestration potential of all UK seas, as well as within Marine Protected Areas (MPAs).  

With two-thirds of the UK underwater, the study will be critical in helping the UK achieve its commitments to achieving net-zero and to protect at least 30% of UK seas for nature by 2030.  

Understanding and mapping blue carbon stores will allow UK Governments to plan and prioritise how we use our marine environments in the future. This includes exploring the impacts of human activities on blue carbon stores.   

A bed of mussels in the foreground with kelp in the background

Mussel bed © Paul Naylor

Saltmarsh at Abbott's Hall in Essex, with a rainbow in a perfect arc in the centre

Saltmarsh at Abbott's Hall © Terry Whittaker / 2020VISION

Stalks of seagrass growing out of the seabed

Seagrass © Paul Naylor

Kelp in the foregound with juvenile fish swimming in the background

Kelp © Dan Smale / Sussex Wildlife Trust

Currently, natural marine carbon stores are thought to be vulnerable to various pressures which can cause them to be disturbed, damaged, or removed entirely. They include bottom-towed fishing gear – used by certain fishing activities such as the scallop industry - and developments at sea and along our coasts – such as offshore energy.  

The project follows a pilot study in the North Sea that was published last year and revealed just how important protecting UK seas are for tackling climate change. The report found:  

  • Carbon stores in the English North Sea amount to nearly 20% of that held in UK forests and woodlands  

  • 98% of the total organic carbon is stored in seabed sediments like sand and mud  

  • Seabed sediments are thus by far the most important habitat for carbon storage in this region  

Dr Simon Walmsley, Chief Marine Advisor at WWF-UK, says:   

“More than two thirds of the UK is under the sea, yet carbon accounting stops on land, creating a substantial blind spot around the carbon storage capacity of UK seas. We need to learn more about this and fast to stop vital marine carbon stores being damaged by human activities.  

“This data will be vital for a range of industries, for futureproofing UK fisheries, and for tackling the climate and nature crises.”  

Dr Lissa Batey, Head of Marine Conservation at The Wildlife Trusts, says:    

“The Government has committed to protecting 30% of the sea by 2030 but the wider seascape is largely being ignored.  From vibrant seagrass meadows to cold water corals, our marine environment is not only rich in wildlife but vitally important for storing carbon and tackling climate change.  

“We are expanding the North Sea study to cover all UK seas, providing us with crucial data that can help determine how we can strategically protect our oceans for wildlife, climate, and people.”  

Kirsten Carter, Principal Policy Officer for the RSPB, says:  

“The increasingly stark warnings of the IPCC and other scientific papers highlights how the nature and climate emergency is affecting all of us, the wildlife we love and the wild places we cherish. This study is bringing together experts from different organisations to look at whether the UK’s network of Marine Protected Areas (MPAs) could be an important asset to our politicians in both protecting species and tackling climate change.  

“On land we have seen that protecting, restoring and creating wild spaces can lead to benefits for our wildlife as well as helping to lock up greenhouse gasses, but to date no one has looked at our marine environment. The results of this study could be a major asset to decision-makers in the UK in seeing how an investment in our network of MPAs will benefit both our iconic wildlife and keep greenhouse gasses locked up.”  

The UK Blue Carbon Mapping project will complete essential research in three regional phases - English Channel/Western Approaches, Irish Sea and Scotland (with the North Sea assessment completed and published last year) - before combining these into a UK summary next year.  

Editor's Notes

  • Blue carbon is the term used for carbon captured by the world’s ocean and coastal ecosystems.   

  • Marine ecosystems, including saltmarsh, seagrass, kelp, seaweeds, biogenic reef and seabed sediments, capture carbon and lock it away. Saltmarsh and seagrass beds both capture and store carbon whereas seaweeds and kelp forests capture carbon, a proportion of which is then eroded and transported elsewhere as detritus and subsequently buried in seabed sediments and stored. Biogenic reefs act principally as depositories for carbon from other sources.    

  • These natural carbon stores are vulnerable to a variety of human pressures which can cause them to be disturbed, damaged or removed entirely, which then hinders or eliminates their ability to store and/or capture carbon.   

  • Protection, restoration and enhancement of marine habitats represent long-term, cost-effective strategies for carbon storage and provide a multitude of additional benefits such as nursery grounds for fish and providing protection to our coastal towns and cities. Long term carbon storage in the sea depends on protecting key habitats from disturbance and damage. The first step is understanding the scale and distribution of carbon stores and capture rates within our seas.   

See report: Assessment of Carbon Capture and Storage in Natural Systems within the English North Sea (Burrows et al., 2021) here. Findings included:  

  • Carbon stocks in the English North Sea amount to nearly 20% of that held in UK forests and woodlands. The top 10cm of English North Sea seabed sediments is estimated to store 100.4Mt carbon. UK forests are estimated to store 529Mt carbon. Seabed sediments are likely to be tens to hundreds of metres in depth so these figures should be considered an underestimate of the total organic carbon stored in the seabed.     

  • 98% of the total organic carbon is stored in seabed sediments like sand and mud. Seabed sediments are thus by far the most important habitat for carbon storage in the region. We have no mechanism for ‘restoring’ these habitats – their protection relies on spatially managing activities so as not to disturb these sediments.  

  • The current English North Sea MPA network contains 51.9% of the total organic carbon stores in the English North Sea and 42.1% of total inorganic carbon stores in the English North Sea.  Almost all of these MPAs are still subjected to broadscale disturbance.     

  • Some areas with the greatest carbon stock density, for example the Devil’s Hole region to the north of the study area, do not lie within an MPA designation and so remain vulnerable to degradation. A huge opportunity exists here to protect significant carbon sinks from disturbance.      

  • While it’s estimated that a potential 1.2 Mt organic carbon are added annually to the sediment stores, disturbance to the seabed from activities including fishing, aggregate dredging, infrastructure development and others means it is unclear how much of this carbon enters the long-term stores. While we continue to disturb the seabed so extensively, we undermine this natural process of locking carbon away.    

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