Global distribution of freshwater biomes. Codes: 1, large lakes; 2, large river deltas; 3, montane freshwaters; 4, oceanic islands; 5, polar freshwaters; 6, temperate coastal rivers; 7, temperate floodplain rivers and wetlands; 8, temperate upland rivers; 9, tropical and subtropical coastal rivers; 10, tropical and subtropical floodplain rivers and wetland complexes; 11, tropical and subtropical upland rivers; 12, xeric freshwaters and endorheic (closed) basins.