EPA Ecoregions

The EPA Ecoregions (ECOR) is a classification system of ecological regions based on similarities and differences in the mosaic of biotic, abiotic, terrestrial, and aquatic components, e.g., climate, vegetation, soil type, landforms, that can affect the quality and integrity of an ecosystem. They are organized into four levels, according to the extent of detail used to define each level. The levels range from Level I, which includes 15 general regions, to Level IV, the most detailed level with >900 finely detailed regions. Maps of North American showing ecoregions Levels I, II, and III are presented with Levels II and III regions nested and displayed inside Level I. Level II has 50 regions that provide an overview of ecological patterns at a national and subcontinental level and Level III has 182 ecoregions which allows more specific ecological characteristics to be defined and enhances environmental monitoring and reporting. Maps of the continental U.S. are also presented which display ecoregions Level III and IV as well as options to view the same two ecoregions in each of the 10 EPA regions or for individual states. Level IV, that provides the finest level of detail, is useful in environmental analysis and monitoring at the local level. All of the maps offered, and their corresponding GIS files, are available for download.