A 10 m dataset of wetland loss and degradation across mainland France (2021)

Description of the dataset The dataset includes three files : France_lost_degraded_wetlands_2021.tif, which is a categorical geotif raster file at 10 m georeferenced in the French projection system (EPSG 2154). It contains four classes: 0 - non-wetland, 1 - existing wetland, 40 - degraded wetland, 50 - lost wetland. This map was derived from the ESA Worldcover V2 2021 product. France_lost_degraded_wetlands_2021.qml, which is the QGIS symbol file associated with the geotiff file. confusion_matrix.docx, which is the confusion matrix between the reclassified ESA Worldcover V2 2021 product (column) and LUCAS field samples (row) using the proportion of area approach (sensu Olofsson et al., 2014). Production of the map of wetland loss and degradation Post classification of the ESA WorldCover V2 2021 product was performed to reduce confusions between built-up and cropland classes with sparse vegetation class in intertidal areas and also between croplands and temporary flooded grasslands as follows : Reassignment of pixels classified as 'Built-up' and 'Cropland' within intertidal areas (based on the highest water level recorded by the French Navy Hydrographic and Oceanographic Service) to the 'Bare / sparse vegetation' class. Raster polygons classified as 'Built-up' and 'Cropland' smaller than 15 and 500 pixels respectively were replaced with the pixel value of the largest neighbour polygon. Pixels classified as 'Cropland' and 'Built-up' on the ESA WorldCover V2 2021 product within wetlands were reassigned to the 'Damaged wetland' and 'Lost wetland' classes respectively. The remaining wetland pixels were reassigned to the class 'Existing wetland'. Map accuraccy assessment The accuracy of the wetland pressure map was assessed using the area of occupancy approach (Olofson et al. 2014) based on 8,870 LUCAS field points collected in 2018 and 2022 within the wetland extent (Rapinel et al. 2023). The overall accuracy is 0.86 (see the confusion matrix included the file confusion_matrix.docx). Lost wetlands account for 4.1% ± 0.1 of the total wetland area in mainland France, compared to 33.2% ± 0.3 for degraded wetlands and 62.6% ± 0.4 for existing wetlands. References Olofsson, P., Foody, G. M., Herold, M., Stehman, S. V., Woodcock, C. E., & Wulder, M. A. (2014). Good practices for estimating area and assessing accuracy of land change. Remote sensing of Environment, 148, 42-57.