(NOTE: maps and GIS files may differ. To make sure you are using the most current ecoregion data, download shapefiles of ecoregions)
GIS data (shapefiles, metadata and symbology):
Map-- available in PDF format:
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. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I is the coarsest level, dividing North America into 15 ecological regions, with level II dividing the continent into 52 regions. At level III, the continental United States contains 99 regions (United States Environmental Protection Agency [USEPA], 1997). Level IV is a further subdivision of level III ecoregions. Explanations of the methods used to define the USEPAs ecoregions are given in Omernik (1995), Griffith and others (1994), and Gallant and others (1989).
This level III and IV ecoregion map was compiled at a scale of 1:250,000; it depicts revisions and subdivisions of earlier level III ecoregions that were originally compiled at a smaller scale (USEPA 1997; Omernik 1987). The poster is part of a collaborative project primarily between the USEPA Region V, the USEPA National Health and Environmental Effects Research Laboratory, Corvallis, Oregon, the Indiana Department of Environmental Management (IDEM), the Ohio Department of Natural Resources (ODNR), the Ohio Environmental Protection Agency (Ohio EPA), the United States Department of Agriculture - Forest Service (USFS), the United States Department of Agriculture - Natural Resources Conservation Service (NRCS) (formerly the Soil Conservation Service), and the United States Department of the Interior - U.S. Geological Survey (USGS) - Earth Resources Observation Systems (EROS) Data Center.
This project is associated with an interagency effort to develop a common framework of ecological regions. Reaching that objective requires recognition of the differences in the conceptual approaches and mapping methodologies that have been used to develop the most commonly used existing ecoregion-type frameworks, including those developed by the USFS (Bailey and others, 1994), the USEPA (Omernik 1987, 1995), and the NRCS (U.S. Department of Agriculture - Soil Conservation Service, 1981). As each of these frameworks is further developed, the differences between them lessen. Regional collaborative projects such as this one in Indiana and Ohio, where agreement can be reached among multiple resource management agencies, is a step in the direction of attaining commonality and consistency in ecoregion frameworks for the entire nation.
Bailey, R.G., Avers, P.E., King, T., and McNab, W.H., eds., 1994, Ecoregions and subregions of the United States (map) (supplementary table of map unit descriptions compiled and edited by McNab, W.H. and Bailey, R.G.): Washington, D.C., U.S. Department of Agriculture - Forest Service, scale 1:7,500,000.
Gallant, A.L., Whittier, T.R., Larsen, D.P., Omernik, J.M., and Hughes, R.M., 1989, Regionalization as a tool for managing environmental resources: Corvallis, Oregon, U.S. Environmental Protection Agency EPA/600/3-89/060, 152 p.
Griffith, G.E., Omernik, J.M., Wilton, T.F., and Pierson, S.M., 1994, Ecoregions and subregions of Iowa - a framework for water quality assessment and management: The Journal of the Iowa Academy of Science, v. 101, no. 1, p. 5-13.
Omernik, J.M., 1987, Ecoregions of the conterminous United States (map supplement): Annals of the Association of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000.
Omernik, J.M., 1995, Ecoregions - a framework for environmental management, in Davis, W.S. and Simon, T.P., eds., Biological assessment and criteria - tools for water resource planning and decision making: Boca Raton, Florida, Lewis Publishers, p. 49-62.
U.S. Department of Agriculture - Soil Conservation Service, 1981, Land resource regions and major land resource areas of the United States: Agriculture Handbook 296, 156 p.
U.S. Environmental Protection Agency, 1997, Level III ecoregions of the continental United States (revision of Omernik, 1987): Corvallis, Oregon, U.S. Environmental Protection Agency - National Health and Environmental Effects Research Laboratory Map M-1, various scales.
Wiken, E., 1986, Terrestrial ecozones of Canada: Ottawa, Environment Canada, Ecological Land Classification Series no. 19, 26 p.
PRINCIPAL AUTHORS: Alan J. Woods (Dynamac Corporation), James M. Omernik (USEPA), C. Scott Brockman (ODNR - Division of Geological Survey), Timothy D. Gerber (ODNR - Division of Soil and Water Conservation), William D. Hosteter (NRCS), and Sandra H. Azevedo (OAO Corporation)
COLLABORATORS AND CONTRIBUTORS: Thomas P. Simon (USEPA), Chris O. Yoder (Ohio EPA), Patrick Merchant (USFS), Thomas R. Loveland (USGS), C. Lee Bridges (IDEM - Office of Water - Biological Studies Section), Gary L. Overmier (NRCS), Kelly Capuzzi (Ohio EPA), Steven A. Newhouse (IDEM - Office of Water - Biological Studies Section), Tom Nash (National Park Service - Cuyahoga National Recreation Area), James R. Gammon (Professor Emeritus of Zoology, DePauw University), Barbara K. Andreas (Professor of Biology, Cuyahoga Community College), and John Harrington (Professor, Department of Geography, Kansas State University)
This project was partially supported by funds from the USEPA - Office of Research and Development - Regional Applied Research Effort (RARE) program.
Please note: In order to ensure cross platform compatibilty (MAC v.s PC) and to provide you with downloadable and printable versions of the maps, the maps themselves are available for download in .pdf (portable document format) format. In order to be able to view and/or print the documents, you will need
Adobe Acrobat Reader, a free download that can be found at