Organic carbon accumulation in British saltmarshes

Craig Smeaton*, Ed Garrett*, Martha Koot, Cai Ladd, Lucy Miller, Lucy McMahon, Bradley Foster, Natasha Barlow, William Blake, Roland Gehrels, Martin Skov, William Austin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Saltmarshes are a crucial component of the coastal carbon (C) system and provide a natural climate regulation service through the accumulation and long-term storage of organic carbon (OC) in their soils. These coastal ecosystems are under growing pressure from a changing climate and increasing anthropogenic disturbance. To manage and protect these ecosystems for C and to allow their inclusion in emissions and natural-capital accounting, as well as carbon markets, accurate and reliable estimates of OC accumulation are required. However, globally, such data are rare or of varying quality. Here, we quantify sedimentation rates and OC densities for 21 saltmarshes in Great Britain (GB). We estimate that, on average, saltmarshes accumulate OC at a rate of 110.88 ± 43.12 g C m-2 yr-1. This is considerably less than widely applied global saltmarsh averages. It is therefore highly likely that the contribution of northern European saltmarshes to global saltmarsh OC accumulation has been significantly overestimated. Taking account of the climatic, geomorphological, oceanographic, and ecological characteristics of all GB saltmarshes and the areal extent of different saltmarsh zones, we estimate that the 451.65 km2 of GB saltmarsh accumulates 46,563 ± 4,353 tonnes of OC annually. These low OC accumulation rates underline the importance of the 5.20 ± 0.65 million tonnes of OC already stored in these vulnerable coastal ecosystems. Going forward the protection and preservation of the existing stores of OC in GB saltmarshes must be a priority for the UK as this will provide climate benefits through avoided emissions several times more significant than the annual accumulation of OC in these ecosystems.
Original languageEnglish
Number of pages12
JournalScience of the Total Environment
Early online date3 Apr 2024
Publication statusE-pub ahead of print - 3 Apr 2024


  • Coastal
  • Blue Carbon
  • Wetlands
  • Radionuclide
  • Climate
  • Nature-based solutions
  • Burial
  • Accumulation
  • Organic carbon
  • UK
  • Scotland
  • Wales
  • England
  • Great Britain
  • Saltmarsh
  • Salt marsh
  • 210Pb sediment dating
  • Chronology
  • 137Cs
  • Isotopes
  • Soil


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