This list provides an overview of United States ecoregions designated by the U.S. Environmental Protection Agency (EPA) and the Commission for Environmental Cooperation (CEC). The CEC was established in 1994 by the member states of Canada, Mexico, and the United States to address regional environmental concerns under the North American Agreement on Environmental Cooperation (NAAEC), the environmental side accord to the North American Free Trade Agreement (NAFTA). The Commission's 1997 report, Ecological Regions of North America, provides a framework that may be used by government agencies, non-governmental organizations, and academic researchers as a basis for risk analysis, resource management, and environmental study of the continent's ecosystems. In the United States, the EPA and the United States Geological Survey (USGS) are the principal federal agencies working with the CEC to define and map ecoregions. Ecoregions may be identified by similarities in geology, physiography, vegetation, climate, soils, land use, wildlife distributions, and hydrology.

The classification system has four levels, but only Levels I and III are on this list. Level I divides North America into 15 broad ecoregions; of these, 12 lie partly or wholly within the United States. Fifty Level II regions were created to allow for a narrower delineation of Level I areas. Three level I areas were not subdivided for level 2. Level III subdivides the continent into 182 smaller ecoregions; of these, 104 lie partly or wholly with the United States. Level IV is a further subdivision of Level III ecoregions. Level IV mapping is still underway but is complete across most of the United States. For an example of Level IV data, see List of ecoregions in Oregon and the associated articles. The classification system excludes the U.S. state of Hawaii, which is not part of the North American continent.

Ecoregions in the United States

Marine West Coast Forest 1 Coast Range 2 Puget Lowland 3 Willamette Valley 111 Ahklun Mountains and Kilbuck Mountains 113 Alaska Peninsula Mountains 115 Cook Inlet 119 Pacific Coastal Mountains 120 Coastal Western Hemlock-Sitka Spruce Forests

The corresponding CEC ecoregion in Canada is called the Pacific Maritime Ecozone.

Western Forested Mountains 4 Cascades 5 Sierra Nevada 9 Eastern Cascades Slopes and Foothills 11 Blue Mountains 15 Northern Rockies 16 Idaho Batholith 17 Middle Rockies 19 Wasatch and Uinta Mountains 21 Southern Rockies 41 Canadian Rockies 77 North Cascades 78 Klamath Mountains 105 Interior Highlands 116 Alaska Range 117 Copper Plateau 118 Wrangell Mountains

The corresponding CEC ecoregion in Canada is called the Montane Cordillera Ecozone.

Mediterranean California 6 Southern and Central California Chaparral and Oak Woodlands 7 Central California Valley 8 Southern California Mountains

North American Deserts

10 Columbia Plateau 12 Snake River Plain 13 Central Basin and Range 14 Mojave Basin and Range 18 Wyoming Basin 20 Colorado Plateaus 22 Arizona/New Mexico Plateau 24 Chihuahuan Deserts 80 Northern Basin and Range 81 Sonoran Basin and Range

Temperate Sierras 23 Arizona/New Mexico Mountains

Great Plains 25 Western High Plains 26 Southwestern Tablelands 27 Central Great Plains 28 Flint Hills 29 Central Oklahoma/Texas Plains 30 Edwards Plateau 31 Southern Texas Plains 40 Central Irregular Plains 42 Northwestern Glaciated Plains 43 Northwestern Great Plains 44 Nebraska Sand Hills 46 Northern Glaciated Plains 47 Western Corn Belt Plains 48 Lake Agassiz Plain

The corresponding name in Canada for the same ecoregion is the Prairies Ecozone.

Eastern Temperate Forest

These forests stretch from the Southern Appalachians towards Canada, up to the northern Midwest. For a general description of these forests, refer to Temperate Deciduous Forest. The standard reference is The Deciduous Forest of Eastern North America.Braun, E. L. 1950. The Deciduous Forest of Eastern North America. New York: Hafner. The adjoining forests in Canada are generally referred to as the Mixedwood Plains Ecozone or the Great Lakes-St.Lawrence Forest Region.

32 Texas Blackland Prairies 33 East Central Texas Plains 34 Western Gulf Coastal Plain 36 Ouachita Mountains 37 Arkansas Valley 38 Boston Mountains 39 Ozark Highlands 45 Piedmont 51 North Central Hardwood Forests 52 Driftless Area 53 Southeastern Wisconsin Till Plains 54 Central Corn Belt Plains 55 Eastern Corn Belt Plains 56 Southern Michigan/Northern Indiana Drift Plains 57 Huron/Erie Lake Plains 58 Northeastern Highlands 59 Northeastern Coastal Zone 60 Northern Appalachian Plateau and Uplands 61 Erie Drift Plain 63 Middle Atlantic Coastal Plain 64 Northern Piedmont 65 Southeastern Plain 66 Blue Ridge 67 Ridge and Valley 68 Southwestern Appalachians 69 Central Appalachians 70 Western Allegheny Plateau 71 Interior Low Plateaus 72 Interior River Valleys and Hills 74 Mississippi Valley Loess Plains 82 Acadian Plains and Hills 83 Eastern Great Lakes and Hudson Lowlands 84 Atlantic Coastal Pine Barrens

Northern Forests 49 Northern Minnesota Wetlands 50 Northern Lakes and Forests 58 Northeastern Highlands 62 North Central Appalachians

The corresponding name in Canada for the same ecoregions are the Boreal Shield and the Atlantic Maritime Ecozones.

Tropical Wet Forests 76 Southern Florida Coastal Plain

Southern Semi-Arid Highlands 79 Madrean Archipelago

Taiga 101 Arctic Coastal Plain 102 Arctic Foothills 103 Brooks Range 104 Interior Forested Lowlands and Uplands 106 Interior Bottomlands 107 Yukon Flats 108 Ogilvie Mountains

Temperate coniferous forest 35 South Central Plains 63 Middle Atlantic Coastal Plain 65 Southeastern Plains 73 Mississippi Alluvial Plain 74 Mississippi Valley Loess Plains 75 Southern Coastal Plain

Tundra 109 Subarctic Coastal Plains 110 Seward Peninsula 112 Bristol Bay-Nushagak Lowlands 114 Aleutian Islands

Listings by state List of ecoregions in California List of ecoregions in Illinois List of ecoregions in Indiana List of ecoregions in Louisiana List of ecoregions in Minnesota List of ecoregions in Oregon List of ecoregions in Wisconsin

See also Ecoregions defined by the Commission for Environmental Cooperation and partner agencies: List of ecoregions in North America (CEC) Ecozones of Canada The conservation group World Wildlife Fund maintains an alternate classification system: List of terrestrial ecoregions (WWF) List of ecoregions in the United States (WWF) List of ecoregions in Canada (WWF)

References

External links State maps of US Level III Ecoregions (Select a state. Then select "Level III Ecoregions")