performance measure that could be used together with specific indicators and performance measures already in place to help to evaluate restoration progress and alternatives, including re-evaluation and refinement of restoration goals.

The proposed system performance indicator does not in itself lead to decisions; instead, it allows alternative scenarios or outcomes to be evaluated. To make decisions, it will be necessary to weight various outcomes and aspects of ecosystem structure and functioning. A recent NRC committee described these considerations in identifying options for protecting Atlantic salmon in Maine (NRC, 2004a). It described the need for “differences in perspectives [to be] taken into account so that the decision is informed by the views of all parties having legitimate interests in the outcome.” Like that earlier NRC committee, this committee cannot perform such weighting, because value judgments are involved, as well as scientific estimates. The best that can be attained is a clear description of a weighting algorithm so that policy makers and stakeholders in the Everglades restoration can do the hard work of agreeing on the weights to be assigned.

Characteristics of a System Performance Measure

In an ideal world, a system performance measure for evaluating alternative Everglades restoration plans would be a single measure of the degree to which a given plan meets the Restoration Plan objectives—water supply and flood control for the built environment, and ecosystem restoration. Such a system measure would need to quantify performance in a way that is consistent with societal preferences. This would mean specifying relative societal preferences both within and across the main categories of water supply, flood control, and ecosystem restoration. How does society value water supply for agriculture versus water supply for municipalities? Restoration of the ridge and slough landscape versus restoration of the marl prairie? Water supply versus flood control? Flood control versus ecosystem restoration?

Obviously, there are many conceptual and practical difficulties in developing an “ideal” system performance measure for Everglades restoration. Some of these difficulties can be avoided by excluding consideration of the built environment and measuring only the degree to which a given restoration plan meets the Restoration Plan ecosystem restoration objectives. To a large extent, Restoration Plan objectives pertaining to the built environment are legally mandated and cannot be compromised without changing the law. (Of course, laws can be changed; an overall ecological performance measure for the Restoration Plan could be used in an analysis to evaluate the degree to which current built environment mandates limit restoration success.)

The Everglades ecosystem consists of several identified, distinct components, such as marl prairie and ridge and slough terrain. Estimation of a system measure of the degree to which a particular restoration plan meets Restoration Plan objectives requires the ability to estimate how the value of a particular ecosystem component is affected by the restoration plan, as well as assignment of relative value to all identified ecosystem components. This clearly means that a system restoration performance measure must be based on restoration outcomes that can be both modeled and valued. Modeling of the Everglades is highly advanced, with respect to both hydrologic and ecosystem processes, although the latter are much more difficult to quantify. In the next section we develop a conceptual system performance measure that focuses on restoration of individual components of the Everglades ecosystem.

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