Functional assessment of a reference wetland set as a tool for science, management and restoration

Abstract.

Wetlands are increasingly becoming the target of efforts to restore or mitigate past and current loss of area and other impacts on their function. Tidal wetlands serve an array of functions deemed beneficial (ecosystem services) but there are relatively few efforts to provide verified indicators of these functions or assess variability in function among wetlands. We assessed twelve functions ranging from wave energy dissipation to fish species richness in tidal freshwater wetlands on the Hudson River. These functions were assessed along with potential "indicators" of function at fifteen marshes selected to span hydrogeomorphic classes as well as expected level of function. Functions varied dramatically among wetland sites, with scores summed across functions ranging from 16% to 70% of the maximum possible. Some of the functions were positively associated such that improvement in one would probably be accompanied by improvements in others. Some functions (e.g., surface water exchange and breeding bird habitat) were negatively correlated indicating that one site cannot maximize all potential functions. A verified reference data set allows more objective selection of targets and sites for restoration as well as establishing realistic goals for what might be achieved. The validated indicators of function are valuable tools for extrapolating from a few intensively studied sites to the larger, unsampled, population of wetland sites in a region.