Organic carbon accumulation in British saltmarshes

Craig Smeaton*, Ed Garrett, Martha B. Koot, Cai J.T. Ladd, Lucy C. Miller, Lucy McMahon, Bradley Foster, Natasha L.M. Barlow, William Blake, W. Roland Gehrels, Martin W. Skov, William E.N. Austin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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 ± 4353 t 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
Article number172104
Number of pages12
JournalScience of the Total Environment
Early online date3 Apr 2024
Publication statusPublished - 20 May 2024

Bibliographical note

Funding Information:
This research was financially supported by the Natural Environment Research Council funded Carbon Storage in Intertidal Environments (C-SIDE) project (grant NE/R010846/1 ) with additional support from the Scottish Blue Forum . Radiocarbon dating was supported by the National Environment Isotope Facility Radiocarbon (Environment) Laboratory (allocation 2351.0321 ). We would like to thank Dr. Mark Garnett for assisting with the radiocarbon analysis and interpretation. We would like to extend thanks to Glenn Havelock, Robert Mills, Fiona Hibbert, Ash Taylor, Trace Laskey and Luke Andrews from the University of York, Simone Riegel, Heather Austin and Will Hiles from the University of St Andrews, Luis Rees-Hughes from the University of Leeds, Subhasree Mohantym and Joseph Apted from the Bangor University, Geoff Millward (University of Plymouth) and Alan Radbourne from UK CEH for assistance in the field and lab. Further we would like to thank members of Nature Scot, Natural Resources Wales, and Natural England for assisting in gaining the required permissions to access and sample saltmarshes around the country.

Publisher Copyright:
© 2024 The Authors


  • Blue carbon
  • Climate
  • Coastal
  • Nature-based solutions
  • Radionuclide
  • Wetlands

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