The ecoregions shown here 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).
Please note this information about the scale of this coverage:
Level III ecoregions were originally compiled using a variety of scale source maps, including some national atlas maps which were 7.5M scale; for that reason, the compilation scale of the level III regions was given as 1:7.5M.
As the level IV ecoregions are being developed (done or in process in all or parts of about 30 states), the level III linework is revised (since the level IV regions nest into the level III regions), as appropriate. The level IV regions are digitized from the 250K quad sheets, along with any changes to the level III boundaries. So, the documentaion that comes with the level III regions is correct, as far as it goes, but also misleading. Until the whole lower 48 has been redone at the level IV scale, the level III regions should still be considered as being compiled at 7.5M, even though pieces of the level III map have been upgraded to 250K.
Procedures_Used:
1) All ecoregion and subregion delineations are digitized from the U.S.G.S. 1:250,000 base maps. Prior to digitizing each base map must be initialized to orient the map and relate it in geographic coordinates to the surface of the earth. When the registration tics are entered at the start of digitizing a transformation error of <0.003 must be achieved in order to insure a high level of registration accuracy. The person responsible for digital data entry completes a data sheet describing coverage name, date of entry, and whether a topology for the coverage is established.
2) After each 1:250,000 base map has been digitized, a topology for each coverage is established. This function creates unique identities for each polygon.
3) Next each base map is tested for polygon errors through an internal editing function. Errors are corrected for unlabeled polygons, unclosed polygons, or polygons with more than one label. Topology is reestablished for each coverage and tested again until no error are indicated.
4) The digital coverage is then plotted at the same scale as the original base map. This coverage is overlaid on a light table with the original and visually inspected for replication of original lines with digitized lines. Two individuals independently inspect the coverage for accuracy.
Revisions:
1. Original lines digitized 1986? (unknown number of revisions between then and now) 2. Updated lines in Ohio and Indiana 1/96 3. updated lines in Tenn. 2/96 4. updated lines western Oregon and Washington 6/6/96 5. updated lines in ND from updated ND level IV lines 9/96 6. updated lines in SD from updated SD level IV lines 9/96 7. deleted # 41 (became part of #42), added 3 new ecoregions (#41, #79, and #80), extended #61 around adirondacks, #34 was extended south to Mexican border. 12/96 8. updated line in SD from revised level IV lines in SD 12/96 9. merged Thompson-Okanaga Highlands ecoregion (79) with Northern Rockies (15). Madrean Archipelago (80) item ECO became 79. 2/97 10. updated line in Ohio, and line in central Oregon from revised lines. 10/97 11. updated lines in Wisconsin from revised level IV lines. 11/97 12. updated lines in Montana from revised level IV lines. 1/98 13. Updated lines to agree with lines from the National Interagency Technical Team (NITT). Areas where lines were altered include Ecoregion 4 in Nothern California, slightly shifted to the west; Ecoregions 36, 37, 38 and 39; ecoregion 73, has a tail going up Red River through Louisiana, into S. Arkansas; ecoregion 12 was split into two, 12 and 80 (Snake River Basin and High Desert); Ecoregion 14 was split into two, 14 and 81; Ecoregion 59 was split in Maine, 59 and 82; ecoregion 61 was split into 61 and 83; ecoregion 63, along the east coast, was split into 63 and 84. 14. Updated lines to agree with level III revisions to AL, GA, and KS. Lines were smoothed using alter and vertex move, add, and delete. Ecoregion names were also updated as follows: region #24 changed from "Southern Deserts" to "Chihuahuan Desert", region #80 changed from "Snake River High Desert" to "Northern Basin and Range", and region #13 changed from "Northern Basin and Range" to "Central Basin and Range". 15. Updated lines in EPA Region 3 from revised level IV lines. Level III lines were also added to NJ separating 63 and 84. Revisions were made for NE representing level IV updates. 3/99Reviews_Applied_to_Data:
1. Lines and map were reviewed by ?? 2. Revised lines were reviewed by Alan Woods, Dynamac 3. Revised lines were reviewed by Glenn Griffith, EPA 4. Revised lines were reviewed by David Pater, Dynamac 5. Revised lines were reviewed by Sandy Bryce, Dynamac 6. Revised lines were reviewed by Sandy Bryce, Dynamac 7. Revised lines were reviewed by Jim Omernik, EPA 8. Revised lines were reviewed by Sandy Bryce, Dynamac 9. Revised line was reviewed by Jim Omernik, EPA 10. Revised lines were reviewed by Sandy Bryce, Dynamac 11. Revised lines were reviewed by Shannen Chapman, Dynamac 12. Revised lines were reviewed by Alan Woods, Dynamac 13. Revised lines were reviewed by Jim Omernik, EPA 14. Revised lines were reviewed by Glenn Griffith, NRCS 15. Revised lines were reviewed by Alan Woods, DynamacRelated_Spatial_and_Tabular_Data_Sets:
USECO.DAT - contains items ECO (Ecoregion Code) and NAME (Ecoregion Name) USECO.LKUP - contains items ECO (Ecoregion code) and SYMBOL (Lookup symbol)Other_References_Cited:
Bryce, S.A., J.M. Omernik, D.E. Pater, M. Ulmer, J. Schaar, J. Freeouf, R. Johnson, P. Kuck, and S.H. Azevedo. 1998. Ecoregions of North Dakota and South Dakota. (Map poster). U.S. Geological Survey, Reston, VA.
Clarke, S.E. and S.A. Bryce. 1997. Hierarchical subdivisions of the Columbia Plateau and Blue Mountains ecoregions, Oregon and Washington. General Technical Report PNW-GTR-395. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, OR.
Commission for Environmental Cooperation. 1997. Ecological regions of North America: toward a common perspective. Commission for Environmental Cooperation, Montreal, Quebec, Canada. 71pp. Map (scale 1:12,500,000).
Gallant, A.L., T.R. Whittier, D.P. Larsen, J.M. Omernik, and R.M. Hughes. 1989. Regionalization as a tool for managing environmental resources. EPA/600/3-89/ 060. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR. 152p.
Gallant, A.L., E.F. Binnian, J.M. Omernik, and M.B. Shasby. 1995. Ecoregions of Alaska. U.S. Geological Survey Professional Paper 1567. U.S. Government Printing Office, Washington D.C. 73 p.
Griffith, G.E. and J.M. Omernik. 1991. Alabama/Mississippi Project. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis OR. 27 p.
Griffith, G.E., J.M. Omernik, and S.H. Azevedo. 1997. Ecoregions of Tennessee. EPA/600/R-97/022. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Corvallis, OR. 51p.
Griffith, G.E., J.M. Omernik, S.M. Pierson, and C.W. Kiilsgaard. 1994. Massachusetts ecological regions project. EPA/600/A-94/111. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR. 58p.
Griffith, G.E., J.M. Omernik, C.M. Rohm, and S.M. Pierson. 1994. Florida regionalization project. EPA/600/Q-95/002. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis OR. 83p.
Griffith, G.E., J.M. Omernik, T.F. Wilton, and S.M. Pierson. 1994. Ecoregions and subregions of Iowa: A framework for water quality assessment and management. The Journal of the Iowa Academy of Science. 101(1):5-13.
Omernik, J.M. 1987. Ecoregions of the conterminous United States. Map (scale 1:7,500,000). Annals of the Association of American Geographers 77(1):118-125.
Omernik, J.M. 1995. Ecoregions: A spatial framework for environmental management. In: Biological Assessment and Criteria: Tools for Water Resource Planning and Decision Making. Davis, W.S. and T.P. Simon (eds.) Lewis Publishers, Boca Raton, FL. Pp. 49-62.
Pater, D.E., S.A. Bryce, T.D. Thorson, J. Kagan, C. Chappell, J.M. Omernik, S.H. Azevedo, and A.J. Woods. 1998. Ecoregions of Western Washington and Oregon. (Map poster). U.S. Geological Survey, Reston, VA.
Wiken, E. 1986. Terrestrial ecozones of Canada. Environment Canada. Ecological Land Classification Series No. 19. Ottawa, Canada.
Woods, A.J., J.M. Omernik, C.S. Brockman, T.D. Gerber, W.D. Hosteter, and S.H. Azevedo. (In press). Ecoregions of Indiana and Ohio. (Map poster). U.S. Geological Survey, Reston VA.
Woods, A.J., J.M. Omernik, D.D. Brown, and C.W. Kiilsgaard. 1996. Level III and IV ecoregions of Pennsylvania and the Blue Ridge Mountains, the Ridge and Valley, and Central Appalachians of Virginia, West Virginia, and Maryland. EPA/600/R-96/077. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Corvallis, OR. 50p.
Limitations_of_Data: For use at 1:250,000 or smaller scales
Attributes: Polygon coverage (.PAT)
Regions:
ECO Ecoregion name 1 Coast Range 2 Puget Lowland 3 Willamette Valley 4 Cascades 5 Sierra Nevada 6 Southern and Central California Chaparral and Woodlands 7 Central California Valley 8 Southern California Mountains 9 Eastern Cascades Slopes and Foothills 10 Columbia Plateau 11 Blue Mountains 12 Snake River Basin/High Desert 13 Central Basin and Range 14 Southern Basin and Range 15 Northern Rockies 16 Montana Valley and Foothill Prairies 17 Middle Rockies 18 Wyoming Basin 19 Wasatch and Uinta Mountains 20 Colorado Plateaus 21 Southern Rockies 22 Arizona/New Mexico Plateau 23 Arizona/New Mexico Mountains 24 Chihuahuan Deserts 25 Western High Plains 26 Southwestern Tablelands 27 Central Great Plains 28 Flint Hills 29 Central Olkahoma/Texas Plains 30 Edwards Plateau 31 Southern Texas Plains 32 Texas Blackland Prairies 33 East Central Texas Plains 34 Western Gulf Coastal Plain 35 South Central Plains 36 Ouachita Mountains 37 Arkansas Valley 38 Boston Mountains 39 Ozark Highlands 40 Central Irregular Plains 41 Canadian Rockies 42 Northwestern Glaciated Plains 43 Northwestern Great Plains 44 Nebraska Sand Hills 45 Piedmont 46 Northern Glaciated Plains 47 Western Corn Belt Plains 48 Lake Agassiz Plain 49 Northern Minnesota Wetlands 50 Northern Lakes and Forests 51 North Central Hardwood Forests 52 Driftless Area 53 Southeastern Wisconsin Till Plains 54 Central Corn Belt Plains 55 Eastern Corn Belt Plains 56 S. Michigan/N. Indiana Drift Plains 57 Huron/Erie Lake Plains 58 Northeastern Highlands 59 Northeastern Coastal Zone 60 Northern Appalachian Plateau and Uplands 61 Erie/Ontario Drift and Lake Plains 62 North Central Appalachians 63 Middle Atlantic Coastal Plain 64 Northern Piedmont 65 Southeastern Plains 66 Blue Ridge Mountains 67 Ridge and Valley 68 Southwestern Appalachians 69 Central Appalachians 70 Western Allegheny Plateau 71 Interior Plateau 72 Interior River Lowland 73 Mississippi Alluvial Plain 74 Mississippi Valley Loess Plains 75 Southern Coastal Plain 76 Southern Florida Coastal Plain 77 North Cascades 78 Klamath Mountains 79 Madrean Archipelago 80 Northern Basin and Range 81 Sonoran Basin and Range 82 Laurentian Plains and Hills 83 Eastern Great Lakes and Hudson Lowlands 84 Atlantic Coastal Pine Barrens