How To Restore An Ecosystem

Restoration is a broad subject because any kind of ecosystem can potentially be restored or created. Some general technical principles are covered in the next sections, while procedures and policies are covered in the following sections.

The Energy Signature Approach

One of the fundamental principles in ecology is that each ecosystem type has a unique energy signature of sources, stresses, and other forcing functions. Thus, the first step in restoration or creation is to ensure that the appropriate energy signature is present on the site where restoration is to occur. Without this step, success of the restoration project is unlikely to occur. There are obvious examples of this approach, such as ensuring a source of water when attempting to create a wetland, but in other cases, detailed knowledge may be needed about the ecosystem. Brinson and Lee (1989) emphasized this approach for wetland restoration in stating "duplication of the energy signature of the replaced wetland is the most critical design consideration." The requirement of the appropriate energy signature is also fundamental when creating a microcosm model of an ecosystem as discussed in Chapter 4.

There are cases in which the whole restoration project revolves around restoring the energy signature itself. At least in a general sense this is true for the multibillion dollar effort to restore the Everglades in South Florida. Here the goal is to restore water flows through the subtropical savanna by reengineering roads, canals, and levees to allow water to pass more freely from Lake Okeechobee to Florida Bay and the Gulf of Mexico. While this single action will not completely restore this highly impacted landscape, it is the most critical aspect of the plan. Another classic case is the restoration of Lake Washington in the Puget Sound region of Washington State (Edmondson, 1991). This lake had been stressed by nutrient additions in secondarily treated sewage from the city of Seattle. These discharges took place through the 1940s and 1950s, until the sewage flows were diverted from the lake. Cultural eutrophication occurred due to the nutrient additions, turning the lake from an oligotrophic state with good water quality conditions to a eutrophic state with poor water quality conditions. Characteristics of the eutrophication process were reduced water clarity and blooms of the blue-green alga (Oscillatoria rubescens), which were stimulated by the nutrients. After diversion of the nutrients, the lake restored itself through self-organization, such that blooms disappeared and water clarity increased. Thus, the lake was restored simply by removing a source (i.e., nutrients in treated sewage) from the energy signature that was not characteristic of the natural lake conditions. Much of lake restoration involves this kind of approach as surveyed by Cooke et al. (1993). A final example of restoration through manipulation of the energy signature occurs with controlled flooding of Grand Canyon in Arizona. This is a case where restoration required the recreation of a disturbance (i.e., flooding) that was characteristic of the natural river ecosystem. The flood-pulse concept (Johnson et al., 1995; Junk et al., 1989) of rivers emphasizes the importance of annual flooding in affecting many physical-biological aspects of the river-flood-plain system (see also Middleton, 2002). Flooding in Grand Canyon has been eliminated by the reservoir storage in Lake Powell (behind Glen Canyon Dam), which is located upstream from the canyon. Hydrology in the river is regulated by water storage in the reservoir and by steady low-flow releases through the dam for hydroelectric power generation. Lack of flooding has stressed the Colorado River in Grand Canyon National Park, especially by altering fluvial geomorphology and encouraging exotic plant species. An experimental flood was tested in 1996 and

Cost of Reclamation

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