The Global Threat of Sinking Deltas

Abstract

River deltas are essential socio-ecological systems, sustaining dense human 30 populations, major economic centers, and vital ecosystems worldwide. Rising sea levels 31 and subsiding land threaten the sustainability of these valuable landscapes with relative sea-level rise and associated flood, land-loss, and salinization hazards. Despite these risks, vulnerability assessments are impeded by the lack of contemporary, high-resolution delta-wide subsidence observations. Here, we present spatially variable surface elevation changes across 40 global deltas using interferometric synthetic aperture radar. Using this dataset, we quantify delta surface elevation loss and reveal the prevalence and severity of subsidence in river deltas worldwide. Our analysis of three key anthropogenic drivers of delta elevation changes shows that groundwater storage have the strongest relative influence on VLM in 10 of the 40 deltas. In the other 2 deltas, the contributions vary with mixed influences from multiple drivers or are dominated by sediment flux or urban expansion. Furthermore, we find that contemporary subsidence surpasses absolute (geocentric) sea-level rise as the dominant driver of relative sea-level rise for most deltas over the 21st century. These findings emphasize the need for targeted interventions addressing subsidence as an immediate and localized challenge, in parallel with broader efforts to mitigate/adapt to climate change-driven global sea-level rise