Freshwater ecosystems regulate the water cycle, support biodiversity and enhance resilience, yet they remain largely overlooked in global climate policies, and most national commitments lack clear, spatially defined targets for their protection and restoration. Here our global map—derived from 30-m land-cover classification, hydrological networks and floodplain models—reveals around 51 million km2 of rivers, wetlands, headwaters, riparian buffers and floodplains that are critical for water security and disaster risk reduction. Overlaying this map on country members of the Freshwater Challenge, we discuss pathways for integrating freshwater ecosystems into nature-based solutions for climate adaptation and mitigation. Furthermore, by analysing areas where forest would naturally occur within our mapped categories, we show that reforesting degraded croplands and short vegetation could sequester 1.07 and 3.41 gigatonnes of CO2 per year, across 355–484 million hectares. These results provide a practical foundation for aligning global climate goals with regional freshwater targets.
