• Wetland habitats can play vital role in tackling climate and biodiversity crises

  • Study backs introduction of UK Saltmarsh Code and carbon trading scheme

While the marshes may have meant danger for Pip in Great Expectations, these wetland habitats are important wildlife havens and mitigate climate change. 

However, since Dickens’s celebrated novel was published in 1860, 85% of England’s saltmarsh has been lost as land has been claimed from the sea for agriculture, development or coastal flood defences. This has resulted in the release of greenhouse gases as well as the loss of biodiversity and natural buffer zones protecting properties and infrastructure from flooding.

The introduction of a carbon credit scheme, enabling companies to invest in the restoration of the UK’s degraded saltmarshes and voluntarily offset their greenhouse gas emissions, would be viable, a study led by the UK Centre for Ecology & Hydrology (UKCEH) has found. 

A partnership of scientists, charities and financial experts investigated the feasibility of a Saltmarsh Carbon Code, similar to the existing Peatland and Woodland codes, which would create a rigorous and scientifically-based voluntary certification standard for saltmarsh carbon to be marketed and traded by UK companies. This would assure buyers of carbon credits that the climate benefits being sold are real, quantifiable, additional and permanent.

The independent study, funded by a UK Government grant, found the introduction of a UK-wide code and carbon credit scheme would be feasible, and provide a pipeline for private investment to contribute to restoration projects, providing there was also some level of public financing in restoration projects. 

So far, there has been relatively limited saltmarsh restoration in the UK, with the majority of schemes to date providing compensatory habitat for damage to designated sites due to development. However, there is an increasing interest by companies in carbon credits, which could accelerate saltmarsh restoration.

At present, the UK only has about 45,000 hectares of natural saltmarsh remaining. It is estimated that these accumulate up to around 700,000 tonnes of CO2 a year and the top 10cm of UK saltmarsh soil hold a total of around 2.3 million tonnes of carbon. 

The total amount of carbon sequestration could increase with effective restoration, which usually involves managed realignment of coastline by deliberating reflooding land to restore a coastal wetland habitat. Saltmarshes trap and bury atmospheric carbon in the sediment beneath them and the vegetation that grows on them.

Saltmarsh, Ribble Estuary. Photo: Stefanie Carter
Saltmarsh in the Ribble Estuary. Photo: Stefanie Carter.

UKCEH wetland scientist Annette Burden led the study, which also involved WWT, RSPB, the University of St Andrews, Bangor University, SRUC, IUCN National Committee UK, Finance Earth and Jacobs. 

She says: “Saltmarshes can play an important role in addressing the climate and biodiversity crises. Restoring sites across the country would support progress towards our net zero targets and provide vital habitat for wildlife, including overwintering migratory birds and commercially important fish species such as Seabass.

“The introduction of a Saltmarsh Code would pave the way for private investment to support projects that have some public financing but would not otherwise happen.”

Varying factors such as ground conditions, design complexity and compensation to landowners mean the cost of restoration can be unpredictable, even after restoration work has begun, which is why public financing is considered essential to cover some of the costs.

The research team looked at how much of the cost of the planned restoration of Old Hall Marshes in Essex could be covered by private investment and reviewed whether carbon finance could have raised enough funds for the managed realignment of Steart Marshes in Somerset which was carried out in 2014. 

The analysis found that with grants, the Steart Marshes scheme would have been able to generate market rate returns for equity investors, and therefore attract sufficient investment to be financially viable. The project team, backed by further Environment Agency/Defra funding, is now developing a pilot Saltmarsh Code for further testing, with the hope that a saltmarsh carbon credits system could be introduced in 2025.

The feasibility study and more information about the ongoing work on the Saltmarsh Code are available on the UKCEH website.  
UKCEH has produced a podcast on the role and importance saltmarshes as part of its Counting the Earth series, as well as a saltmarsh factsheet.

Our scientists are establishing the first network of greenhouse gas monitoring stations on saltmarshes around the UK coast. These flux towers will measure how much carbon dioxide gas is captured from the atmosphere and stored as carbon within the saltmarsh ecosystem.

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Media enquiries

Images of saltmarshes are available on request. For interviews and more information, please contact Simon Williams, Media Relations Officer at UKCEH, via simwil@ceh.ac.uk or +44 (0)7920 295384.

Notes to Editors

The Saltmarsh Code project was funded by a £100,000 grant from the Natural Environment Investment Readiness Fund (NEIRF), an initiative by the Department for Environment, Food and Rural Affairs (Defra), the Environment Agency and Natural England which aims to stimulate private investment to improve and safeguard our natural environment. Ongoing work until March 2025 is funded by a £200,000 grant from the Environment Agency and Defra.

The UKCEH-led saltmarsh feasibility report suggested a price cap of £150 per saltmarsh carbon credit, which is considered by Finance Earth to be a conservative assumption, given the recent significant increases in voluntary carbon prices in the UK and globally. 

The project team suggested the introduction of a UK-wide saltmarsh code, concluding the cost of adopting the VM0033 international verification scheme was likely to make most projects not financially viable.

Given the uncertainty over potential carbon accumulation rates for different saltmarsh sites, the researchers calculated a range of estimates for their two case studies.

About the UK Centre for Ecology & Hydrology (UKCEH)

The UK Centre for Ecology & Hydrology is a world-leading centre for excellence in environmental sciences across water, land and air. We have a long history of monitoring and modelling environmental change.

UKCEH undertakes long-term national surveys of both natural and managed environments, focusing on carbon dioxide, methane and nitrous oxide. We make a major contribution to the UK national and international greenhouse gas emissions inventories, and we improve understanding of the role that land use has on emissions. We are contributing to the development of peatland and saltmarsh carbon codes – voluntary certification standards, enabling peatland and saltmarsh carbon to be marketed and purchased by private investors – thereby providing an income stream for the achievement of national net zero goals. 

The UK Centre for Ecology & Hydrology is a strategic delivery partner for the Natural Environment Research Council, part of UK Research and Innovation.

www.ceh.ac.uk / @UK_CEH /  LinkedIn: UK Centre for Ecology & Hydrology