Terrestrial Ecological Systems of the United States

Classification Concepts and Maps for Ecosystem Assessment, Planning, Management, and MonitoringData, Maps & ToolsUnited States


NatureServe ecologists lead efforts to develop internationally standardized classifications for terrestrial ecosystems and vegetation.  One classification approach is terrestrial ecological systems, mid- to local- scale ecological units useful for standardized mapping and conservation assessments of habitat diversity and landscape conditions. Each ecological system type describes complexes of plant communities influenced by similar physical environments and dynamic ecological processes (like fire or flooding). The classification defines some 800 units across the United States and has provided an effective means of mapping ecological concepts at regional/national scales in greater detail than was previously possible.  

Download U.S. Ecological Data Maps

You may download the national map as a digital file for use in ArcGIS software.

Download the US National Map Conterminous United States (Version 3.0; Updated March 2014) (Compressed file, 3.9GB). NOTE: Use a browser other than Internet Explorer to download this map.

National Map Descriptions (pdf, 4MB, 1176 pages)

Ecological Divisions of the Americas (zip, 13MB)

Information about Ecological Systems is also available in NatureServe Explorer.


In the United States, terrestrial ecological system units have provided the basis for map legends for several national efforts like the USGS Gap Analysis Program and LANDFIRE.

NatureServe ecologists have combined results of these efforts into a national map depicting distributions as of 2003. Since terrestrial ecological systems are linked to the US National Vegetation Classification, this national map information may be displayed at multiple levels of the National Vegetation Classification hierarchy. Ongoing efforts are resulting in maps of these types across the Americas. Updates are planned for 2015 by federal agencies in the United States.


Features & Benefits

Standardized ecological classification units form the foundation for effective data collection, assessment, and reporting on ecosystems.  NatureServe described over 800 mid-local-scale classification units from across the United States. These “terrestrial ecological system’’ units are described using multiple plant communities that tend to co-occur based on recurrent similarities in environmental setting and ecological dynamics.  For example, a given forest or grassland system will describe the predominant plant species composition, landforms, soils, drainage, and natural disturbance dynamics.  Wetland or riparian ecological systems will have similar descriptions, and reference the characteristic hydrologic regime.  All types include a description of their known distribution (e.g., by country, state, and ecoregion).

By integrating environmental setting and dynamic ecological processes with vegetation into the concept of each unit, this classification system lends itself to biophysical modeling and robust characterization of wildlife habitat. These units apply well to land cover mapping and may be augmented with modifiers for specific variants in composition and structure resulting in robust, standardized maps. The inter-agency LANDFIRE effort in the United States uses these concepts to develop conceptual “state-and-transition” models to characterize wildfire regimes.  That effort also produces maps of potential/historical and current distribution for most types nationwide. NatureServe maintains national and regional maps of terrestrial ecological system units. Since vegetation types are used in type description, terrestrial ecological system units provide a direct, systematic link to the US National and International Vegetation Classification.  They also provide a useful framework for integration with land-based “ecological site” concepts and descriptions, as used in the United States for forest and rangeland management applications.