Conservation and Human Alterations of Streams and Rivers

A great challenge for stream and river ecology in the twenty-first century will be the restoration of degraded running-water ecosystems while preserving those systems that still remain in good condition. Restoration will dominate in more developed regions where modifications of running waters and their watersheds have been more extensive. In less-developed regions, preservation of many running waters may still be possible, but the distinction between pristine and degraded systems is disappearing rapidly. The historical scientific databases for running waters are generally poor, with largely anecdotal or very incomplete information available. The lotic ecosystem paradigms described above can serve as tools for evaluating present conditions of running waters, surmising their likely antecedent condition, and developing targets and strategies for restoration. Because the majority of degraded streams and rivers have changed beyond our ability to return them to their historical state, it is more logical to use the term rehabilitation. Often the actions will take the form ofreturning certain organisms or processes to a condition that addresses societal objectives.

In the context of preserving and rehabilitating streams and rivers, it will be important to enlist the best scientific understanding of the structure and function of running-water ecosystems. For example, regulations governing the protection and width of riparian buffer strips, designed to protect stream organisms (usually fish) vary from one area to another, wider in some areas, narrower in others. However, managers and environmentalists should not limit their view of riparian buffers as only a matter of vegetative composition and buffer width with the sole aim of providing shading to reduce water temperatures, a source of large woody debris, or stream bank stabilization. This view of riparian buffers ignores the often completely different in-stream trophic role played by the coupled riparian ecosystem. The buffer width required to produce shade, litter, large wood, nutrients, and bank stabilization are often quite different. Thus, the management and rehabilitation of a given reach of running water requires an integrated approach that acknowledges all the riparian functions and places the actions within the context of the larger watershed.

See also: Desert Streams; Estuaries; Floodplains; Freshwater Lakes; Riparian Wetlands.

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