Mangrove expansion in the Mekong Delta continues despite sea-level rise

Global deltaic mangroves are threatened by accelerated sea-level rise. However, the extent to which accelerated sea-level rise drives landward mangrove migration remains difficult to verify in modern deltas, where concurrent seaward expansion is often driven by sediment delivery. Part of the complication is that interplay of anthropogenic activities and sediment-hydrodynamics in deltas obscures the mangrove response to sea-level rise. Here we analyze the dynamics of the Mekong Delta mangrove shorelines over 496 km through 1992–2024. We find that, despite high rates of relative sea-level rise (RSLR), there was a net mangrove gain of approximately 46300 ha, with three-quarters occurring landward and one-quarter seaward. The observed landward migration was statistically associated with RSLR and occurred where accommodation space was available, while seaward expansion was linked to river sediment supply and modulated by local hydrodynamic processes. Disparities in landward migration between estuarine and coastal regions underscore challenges to mangrove resilience, reflecting how the mangrove response to RSLR is mediated by anthropogenic constraints. This study provides critical insights to inform adaptive management of mangroves under rising sea levels.