Level IV Ecoregions

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. The level IV state projects depict revisions and subdivisions of ecoregions, that were compiled at a relatively small scale (Omernik 1987). Compilation of the level IV maps, performed at the larger 1:250,000 scale, has been a part of collaborative projects between United States Environmental Protection Agency, National Health and Environmental Effects Laboratory (NHEERL)--Corvallis, OR, the U.S. Forest Service, Natural Resources Conservation Service, and a variety of other state and federal resource agencies. The ecoregions and subregions are designed to serve as a spatial framework for environmental resource management. The most immediate needs by the states are for developing regional biological criteria and water resource standards, and for setting management goals for nonpoint-source pollution. Explanation of the methods used to delineate the ecoregions are given in Omernik (1995), Griffith et al. (1994), and Gallant et al. (1989). This series of maps has been produced as part of a regional interagency collaborative project aimed at obtaining consensus between the EPA, the NRCS, and the USFS regarding alignments of ecological regions.

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