EMAP-WETLANDS - A SAMPLING DESIGN WITH GLOBAL APPLICATION

The U.S. Environmental Protection Agency (EPA) initiated the Environme ntal Monitoring and Assessment Program (EMAP) in 1988. The wetland com ponent (EMAP-Wetlands) is designed to provide quantitative assessments of the current status and long-term trends in the ecological conditio n of wetland resources. EMAP-Wetlands will develop a wetland monitorin g network and will identify and evaluate indicators that describe and quantify wetland condition. The EMAP-Wetlands network will represent a probability sample of the total wetland resource. The EMAP sample is based on a triangular grid of approximately 12,600 sample points in th e conterminous U.S. The triangular grid adequately samples wetland res ources that are common and uniformly distributed in a region, such as the prairie pothole wetlands of the Midwest. However, the design is fl exible and allows the base grid density to be increased to adequately sample wetland resources, such as the coastal wetlands of the Gulf of Mexico, which are distributed linearly along the coast. The Gulf sampl e network required a 49-fold increase in base grid density. EMAP-Wetla nds aggregates the 56 U.S. Fish and Wildlife Service's (FWS) National Wetland Inventory (NWI) categories (Cowardin et al. 1979) into 12 func tionally similar groups (Leibowitz et al. 1991). Both the EMAP sample design and aggregated wetland classes are suitable for global inventor y and assessment of wetlands.