Illuminating hotspots of imperiled aquatic biodiversity in the southeastern US

The southeastern United States is a global hotspot for aquatic biodiversity but has relatively little land under protection. To guide conservation investment in this region, we developed a prioritization of watersheds to highlight areas of exceptional conservation potential. Using range maps for 1043 fish, mussel, and crayfish species derived from museum and research collections as well as state natural heritage databases, we derived a conservation priority score for each watershed that incorporates biodiversity, endemism, and imperilment. The highest-scoring watersheds are primarily in the Middle Tennessee River and eastern Mobile River systems. On average, only 1.5% of the area of the top-scoring watersheds is currently protected. Further, average federal spending under the Endangered Species Act is 2.1–46.6 times greater on aquatic species found outside the region than on southeastern endemics. These results provide the foundation for systematic freshwater conservation planning in the Southeast and argue for increased investment in innovative preservation strategies in this globally significant region.