Habitat equivalency in urban estuaries: An analytical hierarchy process for planning ecological restoration

Ecosystem restoration is critically important in urbanized landscapes because habitat degradation is severe and ubiquitous in such areas. Because successful restoration requires specification of desired environmental endpoints, a generally applicable method for valuing and comparing possible restoration endpoints is needed. One method available for comparative valuation is the Analytical Hierarchy Process (AHP). AHP allows a suite of alternatives to be valued on a rank scale based on simple, tractable, paired comparisons among all alternatives. Given a sound technical foundation for the paired comparisons, the method yields an objective set of rank values. By incorporating the relative values of various restoration alternatives in a restoration scaling evaluation such as a Habitat Equivalency Analysis (HEA), restoration programs can be designed effectively both qualitatively (in terms of the kinds of resources or habitats desired) and quantitatively (in terms of the amounts or areas of each). In this study, we develop and apply AHP in the context of a specimen HEA for US Mid-Atlantic coast estuaries. By ranking various habitat types as potential restoration targets based on their value for a suite of key natural resources, a series of restoration ratios is produced, relating relative habitat areas of each type needed to offset specific impairment levels. These ratios provide a basic tool for restoration planning in urbanized estuaries, as these comprise nearly entirely built environments with little or no natural habitat. Under these conditions, restoration planners must specify desired states of the ecosystem, and the restoration ratios allow various permutations of presumed post-restoration environments to be valued and compared.