River and wetland development triggering biological loss.

Giant dams, massive irrigation systems, and widespread logging often bring restricted economic benefits and cause environmental degradation, poverty, and suffering, as well as irreplaceable loss of biodiversity, maintains a Worldwatch Institute report, Imperiled Waters, Impoverished Future: The Decline of Freshwater Ecosystems. Among its findings, billions of dollars spent for flood control, plus the effects of land degradation, actually increased the severity and cost of flooding on the Columbia, Rhine, and Mississippi rivers; pollution and diversion have driven freshwater fisheries into collapse worldwide, and the extinction of freshwater species far outpaces the extinction of mammals and birds; and wetlands worth billions of dollars to the public for fisheries, water purification, and groundwater renewal have been converted to less beneficial uses.

About 20% of 9,000 known freshwater fish species worldwide already are extinct or imperiled, with the toll much higher where human impact is heavy. In North America and Europe, approximately 40% of all native fish species are extinct or imperiled, and in East Africa's heavily stressed Lake Victoria, 40% of its unique 350 native fish species are at risk, with 60% already extinct.

Senior researcher Janet N. Abramovitz, author of the report, emphasizes that, "As alarming as these numbers are, the rate of extinction is even more alarming--a hundred to a thousand times the natural rate. By destroying species faster than nature can create new ones, we are running a "biodiversity deficit' that can never be recovered."

Beyond their obvious benefits for agriculture and industry, intact freshwater ecosystems are vital to human health and economies worldwide. They provide clean drinking water and natural flood control, as well as income and food from fisheries. However, the human desire for immediate profit and "quick fixes" has led to a cascade of damage. Hydroelectric dams, water...