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Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy
using the appropriate soils or plant materials is unlikely to lead to recreating the plethora of functional values of the natural or predisturbed aquatic ecosystem. Although it may seem appropriate to describe as restoration the building of wetlands in backwater areas of a flood control or water supply reservoir, this application distorts the meaning and masks the true purpose of such a created aquatic ecosystem. These ecosystems may be desired in backwater areas for duck habitat and hunting, water quality management, or even additional flood control. However, such created ecosystems will not possess the full range of physical, chemical, and biological characteristics of their natural counterparts. For example, their hydrologic characteristics will differ markedly from the prototype.
The distinctions among the terms restoration, creation, rehabilitation , and reclamation are important, and it is necessary to understand also how these terms relate to mitigation and preservation. Using consistent definitions, scientists and engineers will be better able to communicate their intentions and activities among themselves, policy-makers, and the general public. This should facilitate setting clear goals and establishing effective programs for improving our environment.
STATUS OF AQUATIC RESOURCES IN THE UNITED STATES
This report on the status of our aquatic ecosystems must start with an assessment of the conditions of the land surface. Ninety-seven percent of this country's surface area is land; consequently, most of the water moving into and through aquatic ecosystems interacts with the surface of the land. Of the land surface in the 50 states, comprising 2.3 billion acres, 54 percent is managed for agricultural purposes (Bureau of the Census, 1990). Excluding Alaska, agricultural lands account for 65 percent of the land surface. Of the agricultural lands, 39 percent are grazed and 37 percent are cropped (Frey and Hexem, 1985). Regardless of the activity, the 1.2 billion acres of agricultural land have been substantially altered. Grazing, plowing, chemical applications, and drainage have changed the vegetative cover and soil conditions to such an extent that they no longer exhibit the characteristics of preagricultural conditions. These activities are necessary to support our highly productive agricultural industry, but one of the side effects is the degradation of aquatic ecosystems on a continental scale.
Smaller in scale but more extreme in effect is the alteration of the land surface to accommodate urban development. In building cities, wetlands and floodplains have been filled and made impervious by