Apr. 18, 2000 The U.S. has the most cave-dwelling species worldwide and 95% are imperiled. But protecting cave species should be relatively easy because they are concentrated in less than 2% of the continental U.S., according to new research presented in the April issue of Conservation Biology.
The nearly 1,000 species known to live in caves in the continental U.S. were mapped David Culver of the Department of Biology at American University in Washington DC and his colleagues. Crustaceans, insects and arachnids comprise the majority of cave species and most are eyeless, unpigmented and delicate-looking. These characteristics led people in the 17th century to think that the white salamanders that washed out of caves in eastern Europe were dragon larvae.
The several thousand caves in the continental U.S. are concentrated in the 20% that is covered by 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 of 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 themselves 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, Massachusetts; 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.
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