Oregon Ecoregions, 2010

Oregon Ecoregions, developed and released by Oregon Biodiversity Information Center (ORBIC), March 2010. Based on US EPA Level III Ecoregions, with an additional Marine/Estuary Ecoregion that includes major estuaries and the oceanic nearshore and continental shelf.

Oregon Ecoregions modify the US EPA Level III Ecoregions and are clipped to jurisdictional borders of Oregon. In the Coast Range and Marine/Estuary ecoregions, water/land interfaces, including coastal and riverine islands, and marine and estuarine waters, are presented in much greater detail than the delineations in the EPA shapefile.

[from the original EPA Level III Ecoregion metadata]:
The Level III EPA Ecoregions have been derived from Omernik (1987) and from refinements of Omernik's framework that have been made for other projects.  These ongoing or recently completed projects, conducted in collaboration with
the U.S. EPA regional offices and with state resource management agencies, involve refining ecoregions, defining subregions, and locating sets of reference sites. Designed to serve as a spatial framework for environmental
resource management, ecoregions denote areas within which ecosystems (and the type, quality, and quantity of environmental resources) are generally similar. The most immediate needs are to develop regional biological criteria and water quality standards and to set management goals for nonpoint source pollution.

The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of the patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and integrity (Wiken 1986; Omernik 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. Because of possible confusion with other meanings of terms for different levels of ecologic regions, a Roman numeral classification scheme has been adopted for this effort. Level I is the coarsest level, dividing North America into 15 ecological regions whereas at Level II the continent is subdivided into 52 classes. Level III is the hierarchical level shown on this map. For portions of the United States the ecoregions have been further subdivided to level IV. The applications of the ecoregions are explained in Gallant et al. (1989) and in reports and publications from the state and regional projects. For additional information, contact James M. Omernik, U.S. EPA National Health and Environmental Effects Laboratory (NHEERL), 200 SW 35th St., Corvallis, OR 97333 (phone: 541-754-4458).