The WWF Essex Saltmarsh Chronosequence study

UKCEH and the University of St Andrews researchers will quantify carbon burial and greenhouse gas emissions of adjacent natural and restored saltmarshes in Essex representing 24-122 years since restoration of tidal flow. This will aid future projections of restoration success and predictions of carbon emissions.

UKCEH has previously investigated carbon content of soils and plant communities in natural and restored saltmarshes, however there is a knowledge gap in robust greenhouse gas (GHG) flux estimates needed for the development of the UK Saltmarsh Carbon Code. This Code will enable saltmarsh carbon to be marketed and purchased, providing an income stream for habitat restoration important for carbon storage, biodiversity and coastal defences.

This work will also aid the development of emission factors – a step on the roadmap for potential inclusion of saltmarsh habitat in the UK GHG Inventory.

1. Quantify carbon burial over time in soil cores collected from sets of adjacent restored and ‘natural’ marsh across Essex
2. Quantify GHG emissions over two years in saltmarsh sites of different ages (years since reconnection to tidal flow) to estimate and model change in restored sites over time, and when they reach equivalency with ‘natural’ habitat.

• Saltmarsh soil carbon stocks will be calculated from soil cores collected in 2019 as part of the C-SIDE project. The University of St Andrews are analysing carbon stability and age using radiocarbon dating in the cores to show a timeline of carbon storage.
• Greenhouse gas fluxes are measured monthly for two years using a closed static chamber and portable greenhouse gas analyser as used by UKCEH for peatland research. We will be measuring CO₂, CH₄ and H₂O under different light conditions throughout the year to quantify gross primary productivity, respiration and net GHG fluxes of the saltmarsh system.

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This research will be upscaled to restoration sites across the UK, providing an insight into changes in carbon storage and emissions over long time periods after restoration. The upscaling also provides an opportunity to test our findings and refine emission factors.

This also provides a case for long-term measurements of GHG fluxes as part of the international FLUXNET network, an approach which has underpinned the development of emission factors for peatlands. This data will plug a knowledge gap and contribute towards ongoing development of the UK Saltmarsh Code, and potential inclusion of saltmarshes in the UK GHG Inventory.

This project is funded by WWF.