This
list of ecoregions in the United States 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.