Data are presented showing change in saltmarsh extent along 25 estuaries/embayments in six regions across Great Britain, between 1846 and 2016. Data were captured from maps and aerial photographs. Marsh extent was delineated a scale of 1:7,500 by placing vertices every 5 m along the marsh edge. Error introduced from: (i) inaccuracies in the basemap used to georeference maps and aerial photographs; (ii) the georeferencing procedure itself; (iii) the interpreter when placing vertices on the marsh edge; and (iv) map and photo distortions that occurred prior to digitisation were calculated and used to estimate the root mean square error (RMSE) in areal extent of each marsh complex. Measures of marsh extent were only recorded if maps and aerial photographs were available for the entire estuary/embayment. Data was collected as part of a study on the large-scale, long-term trends and causes of lateral saltmarsh change. The data was used in the analysis for Ladd et al. (2019). C. Ladd and M.F. Duggan-Edwards carried out the collection and processing of the saltmarsh extent data. All authors contributed to the interpretation of the data. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1. Full details about this dataset can be found at https://doi.org/10.5285/03b62fd0-41e2-4355-9a06-1697117f0717

Physical and geochemical measurements of saltmarsh soils produced from 19 wide diameter gouge cores (60 mm in diameter) collected from eight sites encompassing saltmarshes with different origins (natural, historic breach, managed realignment) in 2019. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1 Full details about this dataset can be found at https://doi.org/10.5285/fa3f4087-528e-4c5d-90d8-6bb4675d6317

The dataset comprises of physical property and biogeochemical measurements of saltmarsh soil collected using the hammer coring technique from the Kyle of Tongue saltmarsh in the North of Scotland. The site was chosen to represent northern, loch head marshes and to test different coring techniques in organic rich soils. The data provides a quantitative measure of the dry bulk density, water content, porosity and organic carbon content present within the soils of the Kyle of Tongue saltmarsh. A total of four cores were collected, 39 samples were collected at 10 cm intervals down the length of each core. The samples were processed for bulk density, water content, porosity and organic carbon content which was quantified through elemental analysis. The data were collected to help create a detailed picture of saltmarsh carbon storage in the soils of UK saltmarsh and test different coring approaches. The cores were collected by the data authors in November 2018. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1 Full details about this dataset can be found at https://doi.org/10.5285/b57ef444-54d4-47f9-8cbf-3cfef1182b55