The cumulative effects of climate warming and other human stresses on Canadian freshwaters in the new millennium

Climate warming will adversely affect Canadian water quality and water quan tity. The magnitude and timing of river flows and lake levels and water ren ewal times will change. In many regions, wetlands will disappear and water tables will decline. Habitats for cold stenothermic organisms will be reduc ed in small lakes. Warmer temperatures will affect fish migrations in some regions. Climate will interact with overexploitation, dams and diversions, habitat destruction, non-native species, and pollution to destroy native fr eshwater fisheries. Acute water problems in the United States and other par ts of the world will threaten Canadian water security. Aquatic communities will be restructured as the result of changes to competition, changing life cycles of many organisms, and the invasions of many non-native species. De creased water renewal will increase eutrophication and enhance many biogeoc hemical processes. In poorly buffered lakes and streams, climate warming wi ll exacerbate the effects of acid precipitation. Decreases in dissolved org anic carbon caused by climate warming and acidification will cause increase d penetration of ultraviolet radiation in freshwaters. Increasing industria l agriculture and human populations will require more sophisticated and cos tly water and sewage treatment. Increased research and a national water str ategy offer the only hope for preventing a freshwater crisis in Canada.