A baseline of surface water connectivity in European Ramsar wetlands

Abstract Wetland restoration under the EU Nature Restoration Law prioritises the recovery of surface water connectivity, yet the ways in which water moves and connects across European wetlands remains poorly understood, hindering effective restoration and monitoring. To address this, we analysed ~50 European Ramsar wetlands between 2015 and 2024 using Sentinel-1 satellite imagery and a set of connectivity metrics that capture the spatiotemporal reorganisation of surface water bodies. We show that wetlands with similar inundated areas exhibited very different connectivity patterns, demonstrating that surface water area alone cannot adequately represent wetland hydrological behaviour. Connectivity stability, measured from the repeatability of annual inundation patterns and the timing of connectivity changes, exhibited a strong latitudinal gradient, with northern peatland-dominated wetlands showing the most predictable behaviour. Higher connectivity stability was associated with later snowmelt ( r = 0.57-0.70, p < 0.05) and fewer annual growing degree days ( r = –0.46 to −0.55, p < 0.05). These findings establish a pan-European baseline of surface water connectivity and support hydrologically informed wetland monitoring, restoration, and management.