Global net increase in surface water connectivity in river–floodplain systems

Surface water connectivity in river–floodplain systems—the flow exchange between river channels and their surrounding floodplains—is a regulator of global water cycles, biogeochemical fluxes, geomorphology and ecosystem health. However, global assessments of its spatial and temporal patterns remain limited. Here we use nearly four decades (1984–2019) of satellite observations to analyse changes in connectivity across 1.6 million km, representing 73% of the total global river length. We reveal a net global increase (+3%) in connectivity, with continuous gains observed across 17% of the river length—about 1.5 times the length experiencing continuous losses. These gains are most pronounced in eastern Asia and high-latitude regions, while arid and semi-arid regions exhibit widespread declines. Climatic drivers, including shifts in precipitation and evapotranspiration, predominantly shape these changes, with additional modulation by human activities such as dam construction. Importantly, we identify a strong positive coupling between surface water connectivity and riverine sediment transport in regions experiencing pronounced connectivity changes, underscoring its role in shaping sediment fluxes and associated biogeochemical processes. These findings provide a global record of connectivity in river–floodplain systems and its evolution, offering essential insights to guide sustainable management under escalating climatic and anthropogenic pressures.