List of ecoregions in Arkansas

The level III ecoregions in Arkansas are the South Central Plains (35), Ouachita Mountains (36), Arkansas Valley (37), Boston Mountains (38), Ozark Highlands (39), Mississippi Alluvial Plain (73), Mississippi Valley Loess Plains (74). (Compare to map of Level IV ecoregions.)

This list of ecoregions in Arkansas provides an overview of ecoregions in the U.S. state of Arkansas designated by the U.S. Environmental Protection Agency (EPA) and the Commission for Environmental Cooperation (CEC). The Commission's 1997 report, Ecological Regions of North America, provides a spatial 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.^[1] Ecoregions may be identified by similarities in geology, physiography, vegetation, climate, soils, land use, wildlife distributions, and hydrology.^[2]

The classification system has four levels. Levels III, and IV are shown on this list. Level I divides North America into 15 ecoregions; of these, the entire state is within the Eastern Temperate Forests level. Subdividing the Eastern Temperate Forests, Arkansas is split among three Level II ecoregions: the Southeastern Plains, Ozark, Ouachita, Appalachian Forests, and the Mississippi Alluvial and Southeast USA Coastal Plains. Level III subdivides the continent into 182 ecoregions; of these, seven lay partly within Arkansas's borders. Level IV is a further subdivision of Level III ecoregions. There are 32 Level IV ecoregions in Arkansas,^[2] many of which continue into adjacent areas in the neighboring states of Oklahoma, Mississippi, Missouri, Louisiana, Tennessee, and Texas.

The task of defining and mapping these ecoregions was carried out by the United States Environmental Protection Agency (EPA) Region 6, EPA-National Health and Environmental Effects Research Laboratory (Corvallis, Oregon), and the Multi-Agency Wetland Planning Team.^{[Note 1]} The new classification system they developed may differ from previous frameworks developed separately by the agencies.

Arkansas is ecologically diverse. Though often simplistically split into halves from southwest to northeast, with "uplands" in the northwest half and "lowlands" in the southeastern half, the CEC system of levels reveals the diverse forests and floodplains, prairies and plateaus, ridges and river bottoms, and loess hills and lowlands of Arkansas.^[2]

South Central Plains

35a Tertiary Uplands
35b Floodplains and Low Terraces
35c Pleistocene Fluvial Terraces
35d Cretaceous Dissected Uplands
35g Red River Bottomlands
35h Blackland Prairie

36 Ouachita Mountains

The Ouachita Mountains near Caney Creek, Arkansas

36a Athens Plateau
36b Central Mountain Ranges
36c Central Hills, Ridges, and Valleys
36d Fourche Mountains
36e Western Ouachitas

37 Arkansas Valley

37a Scattered High Ridges and Mountains
37b Arkansas River Floodplain
37c Arkansas Valley Hills
37d Arkansas Valley Plains

38 Boston Mountains

38a Upper Boston Mountains
38b Lower Boston Mountains

39 Ozark Highlands

39a Springfield Plateau
39b Dissected Springfield Plateau–Elk River Hills
39c White River Hills
39d Central Plateau

73 Mississippi Alluvial Plain

73a Northern Holocene Meander Belts
73b Northern Pleistocene Valley Trains
73c St. Francis Lowlands
73d Northern Backswamps
73e Grand Prairie
73f Western Lowlands Holocene Meander Belts
73g Western Lowlands Pleistocene Valley Trains
73h Arkansas/Ouachita River Holocene Meander Belts
73i Arkansas/Ouachita River Backswamps
73j Macon Ridge

74 Mississippi Valley Loess Plains

74a Bluff Hills

Notes

^ Multi-Agency Wetland Planning Team consists of the Arkansas Natural Heritage Commission, Arkansas Soil and Water Conservation Commission, Arkansas Game and Fish Commission (AGFC), Arkansas Department of Environmental Quality (ADEQ), Arkansas Forestry Commission, and University of Arkansas Cooperative Extension Service.^[2]

References

^ "Ecological Regions of North America: Toward a Common Perspective" (PDF). Commission for Environmental Cooperation. 1997. Retrieved January 15, 2018.
^ ^a ^b ^c ^d Woods, A.J.; Foti, T.L.; Chapman, S.S.; Omernik, J.M.; et al. (2004). "Ecoregions of Arkansas (color poster with map, descriptive text, summary tables, and photographs)" (PDF). Reston, Virginia: United States Geological Survey.

Level III Ecoregions in Arkansas

Southeastern Plains

35 South Central Plains

Ozark, Ouachita, Appalachian Forests

36 Ouachita Mountains
37 Arkansas Valley
38 Boston Mountains
39 Ozark Highlands

Mississippi Alluvial and Southeast USA Coastal Plains

73 Mississippi Alluvial Plain
74 Mississippi Valley Loess Plains

as defined by the United States Environmental Protection Agency[1]

v t e Level III Ecoregions in the United States
Marine West Coast Forest	1 Coast Range 2 Puget Lowland 3 Willamette Valley 111 Ahklun and Kilbuck Mountains 113 Alaska Peninsula Mountains 115 Cook Inlet 119 Pacific Coastal Mountains 120 Coastal Western Hemlock-Sitka Spruce Forests
Northwestern 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
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 (Cross Timbers) 30 Edwards Plateau 31 Southern Texas Plains 34 Western Gulf Coastal Plain 40 Central Irregular Plains 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
Eastern Temperate Forest	32 Texas Blackland Prairies 33 East Central Texas Plains 35 South Central Plains 36 Ouachita Mountains 37 Arkansas Valley 38 Boston Mountains 39 Ozark Highlands 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 59 Northeastern Coastal Zone 60 Northern Appalachian Plateau and Uplands 61 Erie Drift Plain 63 Middle Atlantic Coastal Plain 64 Northern Piedmont 65 Southeastern Plains 66 Blue Ridge 67 Ridge and Valley 68 Southwestern Appalachians 69 Central Appalachians 70 Western Allegheny Plateau 71 Interior Plateau 72 Interior River Valleys and Hills 73 Mississippi Alluvial Plain 74 Mississippi Valley Loess Plains 75 Southern Coastal Plain 82 Laurentian 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
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
Tundra	109 Subarctic Coastal Plains 110 Seward Peninsula 112 Bristol Bay-Nushagak Lowlands 114 Aleutian Islands
as defined by the United States Environmental Protection Agency[2]