The United States currently has a scientifically defensible, national system for tracking wetland acreage and loss – the Fish and Wildlife Service (FWS) Status and Trends reports - but lacks a comparable system for documenting trends in wetland condition.  EPA will complement the work of FWS by working in partnership with state, tribal, local, and federal partners, to design and implement a National Wetland Condition Assessment (NWCA).  The NWCA requires a method for identifying a set of candidate reference sites to guide the assessment.

Results/Conclusions

NatureServe, working with EPA and partners, has developed recommendations for establishing reference conditions for all wetlands across the lower 48 states.  Reference wetlands provide a basis for defining what constitutes a characteristic and sustainable level of integrity across a suite of ecological attributes selected for a type. Establishing reference condition of wetlands requires characterizing the variation of wetland types. For a national-scale assessment, broad-scale units of the USNVC and Cowardin classifications are proposed as the primary classifications for helping identify reference sites, with the Hydrogeomorphic Classification providing a supporting role.  Reporting of wetland condition can be completed using both wetland types and an ecoregional framework based on the Omernik ecoregions.  For coordination with state-level assessments, we suggest that finer-scaled classifications, such as NatureServe's Ecological Systems and state wetland types, provide additional interpretive value of wetland condition.  We recommend that existing databases that contain information on reference sites be the primary tool for identifying candidate reference sites.  Database information available from the Network of Natural Heritage programs is particularly relevant.  Where such data do not exist, landscape-based stressor models may be helpful in predicting the most likely places to find reference wetlands.