Riverine flood plains are among the most biologically productive and diverse ecosystems globally, covering over 2 million square kilometers. However, they are highly threatened due to habitat alteration, flow and flood control, species invasion, and pollution. In Europe and North America, up to 90% of flood plains are already 'cultivated' and functionally extinct. In developing regions, the remaining natural flood plains are disappearing rapidly due to changing hydrology. By 2025, further degradation of riparian areas, intensification of the hydrological cycle, increased pollutant discharge, and species invasions are expected. The most threatened flood plains will be in Southeast Asia, Sahelian Africa, and North America. There is an urgent need to preserve existing flood plain rivers and restore hydrologic dynamics, sediment transport, and riparian vegetation to maintain ecosystem services and biodiversity.Riverine flood plains are among the most biologically productive and diverse ecosystems globally, covering over 2 million square kilometers. However, they are highly threatened due to habitat alteration, flow and flood control, species invasion, and pollution. In Europe and North America, up to 90% of flood plains are already 'cultivated' and functionally extinct. In developing regions, the remaining natural flood plains are disappearing rapidly due to changing hydrology. By 2025, further degradation of riparian areas, intensification of the hydrological cycle, increased pollutant discharge, and species invasions are expected. The most threatened flood plains will be in Southeast Asia, Sahelian Africa, and North America. There is an urgent need to preserve existing flood plain rivers and restore hydrologic dynamics, sediment transport, and riparian vegetation to maintain ecosystem services and biodiversity.