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ShareSep. 30, 1999 — The first estimate of extinction rates of North America's freshwater animals shows that they are the most endangered group in the continent. "A silent mass extinction is occurring in our lakes and rivers," says Anthony Ricciardi of the study in the October issue of Conservation Biology.
This research was done by Ricciardi of Dalhousie University in Halifax and Joseph Rasmussen of McGill University in Montreal.
Ricciardi and Rasmussen found that common freshwater species from snails to fish to amphibians are dying out five times faster than terrestrial species. In fact, freshwater animals are dying out as fast as rainforest species, which are generally considered to be the most imperiled on Earth.
If nothing is done, Ricciardi and Rasmussen predict that nearly 4% of freshwater species will be lost each decade. At this rate, many at-risk species will disappear within the next century. Currently, at-risk species account for 49% of the 262 remaining mussel species, 33% of the 336 remaining crayfish species, 26% of the 243 remaining amphibian species, and 21% of the 1021 remaining fish species.
One major threat to freshwater animals is non-native species. For instance, zebra mussels introduced from Europe are outcompeting native mussels in lakes and rivers.
Another major threat to freshwater species is dams. In the contiguous U.S., only about 40 rivers longer than 125 miles remain free-flowing. The fact that hundreds of U.S. dams are coming up for federal re-licensing soon gives us the unprecedented opportunity to re-establish natural flows in many rivers, say the researchers.
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