Mud Matters: How the UK’s Saltmarshes Could Supercharge Climate Action

UK saltmarshes, those muddy tidal wetlands crisscrossed with rivulets and thick marsh grass, are emerging as surprisingly potent climate warriors. A new WWF-Aviva study reveals these landscapes should be counted among the UK’s frontline carbon “sinks,” with seasonal uptake exceeding emissions by a significant margin.

Muddy Guardians of Carbon

Partnering with the UK Centre for Ecology & Hydrology (UKCEH) and RSPB, WWF installed a solar‑powered carbon‑flux tower on the Ribble Estuary. This monitors carbon dioxide exchanges continuously—and shows that saltmarshes absorb more CO₂ in spring and summer than they release in autumn and winter. It’s pioneering work in applying flux‑tower tech, previously used on forests and peatlands, to coastal wetlands 

The BBC highlights that around 85% of England’s saltmarshes have vanished since 1860, leaving roughly 45,000ha remaining across the UK.  UKCEH data estimate the top 10 cm of marsh soil store around 2.3 million tonnes of carbon—while restored sites can sequester between 3–14 t CO₂/ha/yr. That adds up to ~700,000tCO₂ sequestered annually in their current state.

Why Saltmarshes Matter

1. CO₂ Sequestration – UKCEH reports top‑soil carbon stocks of 2.3 Mt; restored marshes capture up to 14 t CO₂/ha each year.

2. Flood Defence – Acting as natural buffers, saltmarshes reduce wave energy and flood risk—WWF estimates their value at over £1 billion for UK homes 

3. Biodiversity – They provide vital habitats for birdlife, fish and otters, and deliver ecosystem services like pollution filtration.

Voices from the Front Line

Tom Brook, WWF’s Ocean Specialist, declared:

“The results are in, and mud matters. Saltmarshes are powerful natural allies in the fight against climate change…” 

Claudine Blamey from Aviva adds:

“The Ribble Estuary saltmarsh flux tower has yielded positive results … confirming … the critical importance of UK saltmarsh in storing carbon.” 

Global Context & Restoration Efforts

A landmark study—State of the World’s Saltmarshes 2025 by the WWF, UKCEH, Blue Marine Foundation and Sky reveals saltmarsh loss at three times the rate of deforestation. Between 2000 and 2019, 1,435 km² have disappeared, releasing ~326 MtCO₂ 

Yet restoration shows promise: 20,000 km² could be reclaimed globally, offsetting 36 Mt CO₂/year 

UKCEH’s March fact‑sheet underlines urgency: with 85% lost, coastal marshes at risk of another 10% loss by 2060 unless action is taken.

Dr Angus Garbutt (UKCEH) emphasizes the potential:

“Minimal investment in restoration projects could deliver significant cost‑effective climate benefits.”

Financing Nature: The Saltmarsh Carbon Code

UKCEH is currently piloting a Saltmarsh Carbon Code, backed by DEFRA/Environment Agency, modelled after the Woodland and Peatland codes. Early findings highlight that restored marshes can sequester 13.3 ± 15.0 t CO₂e/ha/yr but may emit N₂O—so full greenhouse gas accounting is vital. A new UK code could reduce costs and align carbon markets to support restoration 

Homegrown Success: Steart & Severn Projects

The Wildfowl & Wetlands Trust (WWT) is converting 365 acres on Severn Estuary’s Awre Peninsula into marshland—part of a £21 million initiative. Steart Marshes (Somerset) has already sequestered ~30,000 t CO₂ since its 2014 restoration—acting as a research and public engagement hub too 

Kevin Peberdy (WWT) reveals carbon direction:

“Saltmarshes…store vast amounts of carbon – up to 40 times faster than forests.” 

Bringing It All Together

As the WWF spotlight, UK saltmarshes are more than coastlines—they’re climate infrastructure. The emerging flux‑tower data, global status reports, and carbon‑code pilots underline their potential. Yet restoration requires policy shifts, funding, and land‑use planning, especially as marshes vary regionally, North Norfolk and Ribble marshes are struggling to keep pace with sea‑level rise 

Investing in these ecosystems isn’t just greenwash—it offers proven flood protection, biodiversity boosts and validated climate mitigation. With publicly supported carbon codes, saltmarsh restoration can scale fast—and mud truly can matter.