This data set shows Level III ecological regions (ecoregions) of North America and is an update and revision of terrestrial ecoregions released by CEC in 2009. This current cartographic layer consists of an integration of updated ecoregions in Mexico, United States and Canada by the National Institute of Statistics and Geography, the Environmental Protection Agency, and the Government of Canada; Agriculture and Agri-Food Canada, respectively.

Ecoregions are areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. The ecoregions in this data set are based on the premise that a hierarchy of ecological regions can be identified through the analysis of the patterns and the composition of both living and nonliving phenomena, such as geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology, that affect or reflect differences in ecosystem quality and integrity. All the characteristics are considered when determining ecoregions, but the relative importance of each characteristic may vary from one ecoregion to another.

Different levels of ecological regions are identified with a Roman numeral hierarchical scheme. Level I is the coarsest level, dividing North America into 15 broad ecological regions. The 50 level II North American ecological regions provide a more detailed description of the large ecological areas nested within the level I regions and are useful for national and sub-continental overviews of ecological patterns. The 182 level III ecological regions, smaller ecological areas nested within level II regions, enhance regional environmental monitoring, assessment, and reporting, as well as decision-making.

The challenging task of determining North American ecoregions has been the result of research and consultation between federal, state, provincial, and territorial agencies, as well as nongovernmental groups, universities, institutes, and the CEC. This data set represents an update of North American ecoregions derived from national agencies from Canada, the United States and Mexico, aligned with CEC terrestrial ecoregions classification scheme. CEC terrestrial ecoregions classifications represents the working group’s best consensus on the distribution and characteristics of major ecosystems at all three levels across North America.

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