The southeast US region is home to more species of freshwater animals than anywhere else in the world, including nearly two-thirds of all US fish species. Loss of water quality and water diverted for other uses is resulting in rapid drops in many unique species there.
Many freshwater species in the southeast live in karst ecosystems which are underground rivers and lakes that form in limestone rich areas. These unique ecosystems have a large number of animals that are found nowhere else on the planet. The growth of cities and agricultural land use has increased pollution entering these sensitive ecosystems and decreased water levels. Nationally, agriculture accounts for 70% of total water use, and the growth of agriculture in areas such as Florida now threatens many species.
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Karst map from USGS