The several thousand caves in the continental U.S. are concentrated in particular regions. Approximately 20% of the land area of the forty eight contiguous states is covered by cave-bearing rocks, largely limestone. Culver and his colleagues found that cave species are concentrated even further: more than 60% are found only in caves in a single county or even in a single cave. Hotspots of diversity include northeast Alabama for terrestrial cave species and the Edwards Plateau in Texas for aquatic cave species.
While the fact that cave species are concentrated in hotspots will help make it easier to save them, protecting the caves alone is not enough. We must also protect the land above the caves, say Culver and his colleagues.
Nearly all cave species are vulnerable to disruptions of the vegetation and drainage basins of the overlying surface. For example, deforestation around caves can decrease bat and rat populations, thus reducing the dung that many cave species depend on. Dung-dwellers account for an estimated 40% of the U.S. species that live only in caves.
In addition, water-borne contaminants can persist for months in cave ecosystems. Cave streams in West Virginia’s agricultural areas have elevated levels of nitrates and pesticides. Other sources of subterranean water contamination include accidental spills, gasoline storage tank leaks and illegal dumping into sinkholes.
Culver’s co-authors are Lawrence Master of The Nature Conservancy in Boston, MA; Mary Christman of the Department of Mathematics and Statistics at American University in Washington DC; and Horton Hobbs of the Department of Biology at Wittenberg University in Springfield, Ohio.
For more Information
Culver, D.C., L.L. Master, D.W. Sinaga, and A.H. Mustari. 2000. Obligate cave fauna of the 48 contiguous United States. Conservation Biology 14(2):386-401.
David Culver, 202-885-2180