Abstract and study scope

The researchers mapped six natural and seminatural open wetland types across large parts of Europe at 10-m resolution, with overall accuracy of 96.6 ± 0.3%, covering an estimated 413,504 ± 17,782 square kilometres, or 6.8 ± 0.3% of the respective land surface. They used an XGBoost machine-learning algorithm trained on 101,000 CORINE Land Cover-labelled sample points and applied it to a multisensor satellite data cube spanning 2017–2019. The predictor set combined optical and radar observations from more than 470,000 Sentinel-1 and Sentinel-2 scenes with auxiliary layers on topography, climate, biomes and soil. An independent validation sample and design-based area estimates were used. European wetlands were fine-grained and highly fragmented: 27–33% of wetland area occurred in map-defined patches smaller than 25 hectares and 7–11% in patches smaller than 1 hectare. Small-patch prevalence was greatest for inland marshes, with 48.8% below 25 hectares and 19.8% below 1 hectare, while intertidal flats had the lowest shares. Coarser inventories commonly miss wetlands below 25 hectares and below 1 hectare.

The study classified wetlands overlapping agricultural or urban land-use classes as most disturbed, those within 150 metres as intermediately disturbed and all others as least disturbed. It estimated that 20.4% ± 3.4% of Europe’s wetland area was affected by anthropogenic disturbance, with 13.6% ± 3.0% classified as most disturbed. Inland marshes were the most disturbed class, with nearly half of their area classified as most disturbed; about 36% of salt-marsh area and about 21% of peatbog area showed human influence. Disturbance-associated soil carbon storage differences under 2018 conditions were estimated at 0.8–4.9 Gt CO2-equivalent, roughly 10–11% of the mean soil-carbon storage pool, but these are potential stock differences rather than annual emission rates. The researchers estimated that 2.66 million hectares of wetlands would need restoration by 2030 across the EEA38. Country needs varied widely, with the United Kingdom, Ireland, Turkey and Romania accounting for a large share. The target areas are scenario-based and should not be interpreted as exact legal obligations or implementation plans.