| Few boreal waters are managed in a sustainable manner, because cumulative effects of a variety of human activities are not considered. Fisheries and water quality have declined in most large water bodies of the southern boreal zone. Some of the reasons are direct, including overexploitation of fisheries, alteration of flow patterns, introductions of non-native species, and discharge of eutrophying nutrients and persistent contaminants. However, improper management of watersheds and airsheds also causes degradation of aquatic ecosystems. Clear-cut logging, climatic warming, acid precipitation, and stratospheric ozone depletion are among the more important of these indirect stressors. There are important interactions among these stressors, requiring that... |
