River Habitats Have Been Heavily Altered
Notes:
Waterways Altered for Navigation, 1680-1980
Dams and channelization remain the two most pervsive threats to freshwater ecosystems today, with dramatic effects on species abundance and diversity. The scale and extent of these human impacts on freshwater systems have risen precipitously in recent years. In 1950, there were 5,270 large dams; today, there are more than 36,500. For more information see http://www.wri.org/trends/freshwat.html.
Source: Janet N. Abramowitz, “Imperiled Waters, Impoverished Future: The Decline of Freshwater Ecosystems,” Worldwatch Paper No. 128 (Worldwatch Institute, Washington, D.C., 1996), p. 13.