Vegetation loss and response to hydrological drought on the islands of the Congo River

Study Region The study focuses on floodplain islands along a ~400 km reach of the middle Congo River between Mbandaka and Mpouya in the Democratic Republic of Congo. The study area contains approximately 800 geomorphologically stable river islands covering roughly 1040 km² and supporting vegetation ranging from early successional grasses and shrubs to mature forests, alongside small-scale fishing and agriculture. Study Focus This study investigates vegetation responses to the 2024 hydrological drought across Congo River islands and examines how hydroclimatic conditions propagated through the river-floodplain system. Hydrometeorological conditions were characterised using CHIRPS precipitation data, ERA5-Land temperature and evaporation, and HydroWeb altimetry river stage records. Drought severity was assessed using SPEI-3, consecutive dry days, and warm day frequency. Vegetation change was evaluated using spectral indices and supervised land-cover classification derived from cloud-free Sentinel-2 Level-2A imagery. New Hydrological Insights for the Region The 2024 event was characterised by persistent precipitation deficits and elevated temperatures, followed by below-average river levels consistent with reduced upstream discharge and the development of hydrological drought. Vegetation decline closely coincided with lower river stage, suggesting that reduced river–floodplain connectivity contributed to drought impacts on floodplain vegetation. Vegetation loss was greatest in shorter vegetation, suggesting that vegetation structure influences ecosystem sensitivity to water limitation.