Coupled pollution and water scarcity heighten ecological degradation and social vulnerability in global dryland rivers

Dryland rivers, historically central to human development in water-scarce regions, now face compounding threats from pollution and climate change that jeopardize both ecosystems and socio-economic stability. This study provides the first global systematic synthesis, based exclusively on previously published secondary data, integrating chemical, hydrological, and socio-economic data across nine major dryland rivers spanning four continents: Limpopo and Nile (Africa), Amu Darya and Shule (Asia), Darling (Oceania), and Colorado, Conchos, Grande/Bravo, and Loa (Americas). A cross-matrix analysis of water, sediment, and biota revealed that over 70 % of sites reported contaminant concentrations exceeding international safety thresholds. Legacy pollutants-particularly metalloids (As, Hg, Cd, Pb) and persistent organic compounds (PCBs, PAHs, DDT)-were detected in more than 80 % of the studied rivers, often accumulating in sediments and aquatic organisms. These pollutants, coupled with declining discharge and rising aridity, intensify ecological stress and reduce ecosystem resilience. Socio-economic assessment indicates that communities in more than half of the basins experience medium to high levels of economic loss, health impacts, or conflict, reflecting the intersection of environmental degradation and human vulnerability. By linking quantitative pollutant data with hydrological and socio-environmental indicators, this study provides the first global evidence that pollution and water scarcity jointly amplify ecosystem and human vulnerabilities in dryland rivers, underscoring the urgent need for standardized transboundary monitoring, integration of socio-economic metrics in water governance, and adaptive management strategies to enhance resilience in dryland regions globally.