North American Terrestrial Ecoregions

This data set shows Level I, II, and III ecological regions (ecoregions) of North America, and is an update and revision of files developed by Canada, Mexico, and the United States of America in the late 1990’s in a cooperative project for the Commission for Environmental Cooperation (CEC).These revised ecological regions were developed in a meeting between representatives of the three nations and CEC in April 2006 in Newport, Oregon.

      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. These highlight major ecological areas and provide the broad backdrop to the ecological mosaic of the continent, putting it in context at global or intercontinental scales. 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 181 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 the working group’s best consensus on the distribution and characteristics of major ecosystems at all three levels across North America.