Functional versus geographic isolation of wetlands: Using organisms to indicate status

Background/Question/Methods

Small, temporally dynamic, biologically diverse isolated wetlands are among the most imperiled ecosystems worldwide, yet their conservation is hindered by the lack of protective legislation and an established definition for the term ‘isolated wetland’. Defining the term ‘isolated wetland’ presents many issues associated with the inherent variability of these ecosystems. One method for circumventing the need for a definition is to create an assessment system to categorize these ecosystems. Assessment systems based on hydrological and geophysical characteristics exist for classifying isolated wetlands in the United States, but these assessment systems do not adequately describe wetlands that biologically function as isolated wetlands in regions that were not formerly glaciated. We sought to develop an assessment system for isolated wetlands that would allow land managers to categorize these wetlands for regulation. Using remote sensing and local ecological knowledge, we mapped wetlands in the Piedmont and Blue Ridge regions of South Carolina. We gathered data on the abiotic and biotic characteristics of 41 of these wetlands through multiple site visits over a two year period. We devised a decision tree for classifying isolated wetlands in the Blue Ridge and Piedmont regions of the southeastern United States.

Results/Conclusions

Wetlands that functioned as ‘isolated’ wetlands were physically and biologically diverse and varied in degree of hydrological connectivity. Species considered ‘isolated wetland-dependent’ species did not require wetlands that were completely geographically isolated and readily used wetlands that were at least temporarily connected with other aquatic systems. We term these ‘functionally isolated’ wetlands and suggest many would qualify for conservation and regulation under existing legislation associated with the Clean Water Act. However, many ecologically important, hydrologically isolated wetlands are left unprotected based on existing laws. We suggest that new legislation be developed and implemented that will allow for the conservation and regulation of these currently unprotected, ecologically important wetlands based on assessment of biodiversity function, rather than hydrological connectivity.