Lundi 17 avril 2023 à 11h00, Etienne Fluet-Chouinard – ETH Zurich, Zurich, Suisse – présentera en salle Jean-Paul Taris un séminaire/webinaire intitulé :
« Reconstructing global wetland loss from land use conversion over 1700-2020 »
Wetlands have long been drained for human use, thereby strongly affecting greenhouse gas fluxes, flood control, nutrient cycling and biodiversity. Nevertheless, the global extent of natural wetland loss remains remarkably uncertain despite numerous reports of high regional losses. In this presentation, I will discuss a new method to reconstruct the spatial distribution and timing of global wetland loss through conversion to seven human land uses (cropland, forestry, peat extraction, wetland cultivation, rice cultivation, pastures, urban areas) between 1700 and 2020, by combining national and subnational records of drainage and conversion with land-use maps and simulated wetland extents (Fluet-Chouinard et al. 2023 – Nature). This approach estimates that 3.4 million km2 (confidence interval 2.9–3.8) of inland wetlands have been lost since 1700, primarily for conversion to croplands. This net loss of 21% (confidence interval 16–23%) of global wetland area is lower than that suggested previously by extrapolations of data disproportionately from high-loss regions. Wetland loss has been concentrated in Europe, the United States and China, and rapidly expanded during the mid-twentieth century. I will also discuss the role of regional estimates of wetland loss in calibrating and validating the reconstruction as well as next steps to improve the resulting global map. The new reconstruction elucidates the timing and land-use drivers of global wetland losses, providing an improved historical baseline to guide assessment of wetland loss impact on Earth system processes, conservation planning to protect remaining wetlands and prioritization of sites for wetland restoration.
Note: The presentation will be in French while slides will be in English.