Overview
- Researchers produced the first high‑resolution, delta‑wide map of vertical land motion across 40 major deltas using InSAR, resolving changes at 75 square meters.
- Subsidence already exceeds local sea‑level rise in 18 deltas, elevating near‑term flood risk for more than 236 million people.
- Deltas with some of the highest rates include the Chao Phraya, Mekong, Nile, Ganges–Brahmaputra, Yellow River, and Mississippi, with average sinking near 4 millimeters per year and hotspots at more than twice the global sea‑level rise rate.
- Groundwater withdrawal is the dominant predictor of sinking land, with reduced river sediment supply and urban expansion also driving regional variability.
- The authors call for immediate, locally targeted actions such as cutting groundwater pumping and managed aquifer recharge, alongside investments to expand and publicly share subsidence monitoring.