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. Ecoregions may be identified by similarities in geology, physiography, vegetation, climate, soils, land use, wildlife distributions, and hydrology.
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, 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. 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.