NCEA Saltmarsh Network Analysis Ready dataset, comprised of spatial layers used in ecological monitoring and reporting, Natural Capital Ecosystem Assessments, and for coastal flood and erosion risk management:
Saltmarsh Extent & Zonation (VE501Z406) layer : Polygon data layer showing the extent of saltmarsh in England mapped from aerial photography predominantly collected between 2016 and 2024.
Over 95% of the national extent has been mapped to zonation level. Zonation classes are as follows: • Pioneer • Spartina • Mid-low • Upper Marsh • Reedbeds • Unclassified (saltmarsh, but not classified to zonation level) • Not Saltmarsh (small areas of bare ground, standing water or other vegetation found within saltmarsh beds) These zones reflect ecological communities within saltmarsh habitats required for ecological assessment purposes.
Saltmarsh Extent latest (VE501) layer: Polygon data layer showing the extent of saltmarsh in England mapped from aerial photography predominantly collected between 2016 and 2024.
Saltmarsh Extent Baseline (VE108) Layer: polygon extent layer represents a baseline from which later rounds of extent mapping can be compared to. Mapped from aerial photography predominantly collected between 2006 and 2009.
The Saltmarsh Change layer: polygon layer created by comparing the 'baseline' version (VE108 ) of Saltmarsh Extent inventory with its 'most recent' version (VE5_01 ). Since the production of the baseline (in 2006-09), almost 100% of England's saltmarsh has been remapped using later imagery.
This dataset allows users to easily identify the differences between the two versions of the mapped extent and identifies where areas of gain and loss have occurred. Each feature within the dataset has been assigned one of the following change attribute classes: • Gain • Loss • No Change • Not Remapped The dataset provides valuable evidence of where saltmarsh is accreting and eroding across the whole of England, which is vital for use in ecological monitoring and reporting, Natural Capital Ecosystem Assessments, and for coastal flood and erosion risk management.
The demarcation of the landward extent is aimed to be the point at which the upper most zones give way to terrestrial plants (often at the foot of a seawall), and where saltmarsh plants become ≤5% of the predominantly terrestrial community. At the seaward end, the final demarcation is aimed to be where the saltmarsh vegetation cover has become so sparse that it only represents <5% of the ground cover. How the saltmarsh has been defined is described in detail in the sample framework report.
The mapped extents and zonation were ground-truthed, using data collected by the Environment Agency and Natural England through a combination of national monitoring programmes and additional NCEA monitoring from 2023 onwards.
Many improvements and updates to the data layer have been generated through the NCEA programme. Additional attribution includes geographical unit location such as WER Water Body. The quality of attribution has also been improved by applying a strict data schema and cleaning protocol. NCEA programme ground survey data have also been used to improve the accuracy of the zone classification.
The Natural Capital and Ecosystem Assessment (NCEA) programme is Defra’s largest Research and Development (R&D) programme and the most ambitious assessment of the state of nature ever undertaken in the UK. NCEA is assessing England's land, freshwater, and coastal ecosystems to produce a baseline of our natural assets by 2029, enabling a natural capital approach to policy and investment.
The NCEA Saltmarsh Network is a project supported by the UK Government through Defra's Natural Capital Ecosystem Assessment (NCEA) programme. Users should ensure they have read the NCEA Analysis Ready Data Limitations Statement and dataset specific limitations/ caveats outlined in the Data Dictionary
Managed Realignment Site (MRS) data included in this dataset is used with permission courtesy of https://www.omreg.net/resources/ Attribution statement: © Environment Agency copyright and/or database right 2025. All rights reserved.
