Shifting Shores: Carbon Storage and Habitat Resilience in a Major Scottish Saltmarsh

Saltmarshes are dynamic but vulnerable coastal ecosystems that play an important role in blue carbon sequestration, nature conservation, and flood defence. Shifting river channels, rising sea levels and increased storm frequency threaten these habitats, potentially disrupting the delicate balance of accretion and erosion. However, this study of Caerlaverock merse, Scotland’s largest saltmarsh, reveals a habitat that adapts to environmental change through vertical and horizontal accretion, and new terrace formation. An analysis of 293 cores shows an organic carbon (OC) stock of 43.6 ± 6.6 kt in the top 30 cm of saltmarsh sediment, with OC density increasing from pioneer through to upper merse. High-resolution aerial photography shows net areal accretion of merse over the period 2015–2021 highlighting the saltmarsh’s resilience in maintaining blue carbon stocks and critical ecosystem services. Nevertheless, because higher OC-content middle merse is being eroded and replaced with accreted pioneer merse, there is a net OC loss in the short term, though with longer term succession to lower and middle merse, this deficit will be reversed. These findings provide valuable insights for conservation and management strategies in response to changing climatic conditions.