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Ecoregions

About Ecoregions

Ecoregions, which are ecosystems of regional extent, in the United States, Puerto Rico, and the U.S. Virgin Islands.
Ecoregions, which are ecosystems of regional extent, in the United States, Puerto Rico, and the U.S. Virgin Islands.
Ecoregions are large areas of similar climate where ecosystems recur in predictable patterns. The Rocky Mountain Research Station provides resources and education on the origins of these patterns and their relevance to sustainable design and planning.

The ecoregion classification system includes four levels of detail to show a hierarchy of ecosystems. The largest ecosystems are domains, which are groups of related climates and which are differentiated based on precipitation and temperature. Divisions represent the climates within domains and are differentiated based on precipitation levels and patterns as well as temperature. Divisions are subdivided into provinces, which are differentiated based on vegetation or other natural land covers. The finest level of detail is described by subregions, called sections, which are subdivisions of provinces based on terrain features. Also identified are mountainous areas that exhibit different ecological zones based on elevation.

Detailed descriptions of ecoregions at the domain, division, and province levels are available for the contiguous United States. Section-level descriptions are also available, as well as marine ecoregions.

Who Uses Ecoregions?

Many federal agencies and private organizations use a system of land classification based on the ecoregion concept. Some of these include USDA Forest Service, U.S Geological Survey, U.S. Fish and Wildlife Service, The Nature Conservancy, and The Sierra Club. Projects include biodiversity analysis, landscape and regional level forest planning, and the study of mechanisms of forest disease:

More Information on Ecoregions

Download Maps and GIS Data Sets

Shapefiles of ecoregions for the contiguous United States are available here through the U.S. Geological Survey.

In addition, the USDA Forest Service and the National Atlas of the United States® collaborated to create, and deliver for download, the following GIS data sets:

Posters

A map of the ecoregions of the United States is available for download as a .jpeg image (2.1MB compressed).

Contact Robert Bailey to receive a copy of the following posters:

  • Ecoregion-Based Design for Sustainability (2002), 22" x 34", Color, Rolled or Folded

  • Ecoregions (1998), 22" x 34", Color, Rolled or Folded

  • Ecosystem Geography (1996), 22" x 34", Color, Rolled or Folded

Publications

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Books

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The first edition of this book (1998) classified and characterized the regional-scale ecosystem units (ecoregions) of the Earth as shown on a map that Bailey developed with the encouragement of several international organizations. Bailey is one of the pioneers that conceived and developed the ecoregion concept; in addition to the descriptive account, his primary goal was to suggest explanations that act to produce the global pattern of ecoregion distribution, and to consider some of the implications for land use. He includes ocean types, since understanding land regions depends on understanding ocean systems. This second edition is a completely updated and expanded version. New sections address how ecoregions change under the relentless influence of humans and climate change, and include discussions of the use of eco-regional patterns to transfer research results and select sites for detecting climate change effects on ecosystem distribution.

The first edition of this book (1996) explores the patterns of ecosystem distribution at multiple scales. It describes these patterns in terms of the mechanisms that cause them, and goes on to examine the connections between these patterns, conservation, and management. This second edition builds on the strengths of its predecessor, incorporating new information and clarifying concepts. New sections address how ecoregion boundaries were determined, discuss ecoregion redistribution under climate change, put more emphasis on ecosystem processes (such as fire regimes), and describe human modification to ecosystems, such as through the introduction of invasive species.

This richly illustrated volume completes Robert G. Bailey's celebrated study of ecoregions, begun in the landmark Ecosystem Geography (1996) and further articulated in Ecoregions (1998). In this third installment, the author expands his system for defining large-scale ecological zones to encompass principles of land management, regional planning, and design. In an engaging, nontechnical discussion, he shows how larger patterns and processes that characterize a region — its climate, topography, soils, vegetation, fauna, and human culture — provide essential keys to the sustainability of ecosystems.

Journal Articles

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Designers of the structures at Colorado's Mesa Verde National Park diverged from the National Park Service's architectural tradition at the time. The historical precedent was to borrow attractive yet incongruous design themes from the Old World with little regard for the natural setting. Instead, principal designers Jesse and Aileen Nusbaum became the first to incorporate surrounding ecological themes into the design of a National Park structure.

This article summarizes the rationale used in identifying ecoregion boundaries on maps of the United States, North America, and the world's continents, published from 1976 to 1998. The geographic reasoning behind boundaries involves 20 principles, which are presented to stimulate discussion and further understanding.

Many state and federal agencies have begun using watershed or ecoregion frameworks. Misunderstanding of each of the frameworks has resulted in inconsistency in their use and ultimate effectiveness. The focus of this paper is on the clarification of both frameworks. The issue is not whether to use watersheds or ecoregions frameworks, but how to correctly use the frameworks together.

World-wide monitoring of agricultural and other natural-resource ecosystems is needed in assessing the effects of possible climate changes and/or air pollution on our global resource-base. Monitoring of all sites is neither possible nor desirable for large areas, and so a means of choice has to be devised and implemented.

As part of the planning process, maps of natural factors are often superimposed in order to identify areas which are suitable or unsuitable for a particular type of resource management. Current interest in applying computer-assisted mapping technology is drawing attention to geographic information systems. The resultant maps, however, may be so inaccurate that they could lead to imperfect or false conclusions. Recommendations are made on how to proceed in light of these problems.

Natural resource management occurs at varying levels from national to site-specific, creating the need for a hierarchical system of ecosystem units, defined according to criteria that make them relevant to the kinds of questions being asked at different levels of management decisions. A set of criteria for sub-dividing a landscape into ecosystems of different size is presented, based on factors important in controlling ecosystem size at varying scales in a hierarchy.

Ecosystems come in many scales or relative sizes. The relationships between smaller and larger scales must be examined in order to predict the effects of management prescriptions on resource outputs. Environmental factors important in controlling ecosystem size change in nature with the scale of observation. Environmental factors that are thought to be useful in recognizing and mapping ecosystems at various scales are reviewed.

As a means of developing reliable estimates of ecosystem productivity, landscapes need to be stratified into homogeneous geographic regions. Such ecosystem regions are hypothesized to be productively different in important ways. One measure of the difference is hydrologic productivity. Data from 53 hydrologic bench-mark stations within major ecosystem regions were subjected to discriminant analysis. The ecosystem regions tested in this study exhibit a high degree of ability to circumscribe stations with similar hydrologic productivity.

As a means of developing reliable estimates of ecosystem productivity, ecosystem classification needs to be placed within a geographical framework of regions or zones. This paper explains the basis for the regions delineated on the 1976 map Ecoregions of the United States. Four ecological levels are discussed — domain, division, province, and section — based on climatic and vegetational criteria. Statistical tests are needed to verify and refine map units.

Government Publications

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  • Bailey, Robert G. 2010. Fire regimes and ecoregions. Pp 7-18 in Elliot, William J.; Miller, Ina Sue; Audin, Lisa (eds.). Cumulative watershed effects of fuel management in the western United States. General Technical Report RMRS-GTR-231. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

The majority of American forest and grassland ecosystems are adapted to fire of varying frequencies and magnitudes. Fire-excluded systems are prone to changes in composition and density, and are susceptible to catastrophic fire and invasion by non-native species. Planning for fire and land management policies must incorporate an improved understanding of fire regimes. This paper discusses fire regimes of different ecosystems at the scale of ecoregion, and goes on to explore how understanding fire regimes can abate the threat of fire exclusion and restore fire-adapted ecosystems.

  • Bailey, Robert G. 2009. Research applications of ecosystem patterns. Pp 83-90 in McRoberts, Ronald E.; Reams, Gregory A.; Van Deusen, Paul C.; McWilliams, William H. (eds.). Proceedings of the eighth annual forest inventory and analysis symposium; 2006 October 16-19; Monterey, CA. General Technical Report WO-79. Washington, DC: U.S. Department of Agriculture, Forest Service.

This article discusses the origins of natural ecosystem patterns from global to local scales. It describes how understanding these patterns can help scientists and managers in two ways. First, the local systems are shown within the context of larger systems. This perspective can be applied in assessing the connections between action at one scale and effect at another, the spatial transferability of models, and the links between terrestrial and aquatic systems. Second, scientists and managers can benefit because they are given information about the geographic patterns in ecosystems. Consequently, they are in a better position to design sampling networks, transfer knowledge, and analyze ecosystem diversity.

  • Bailey, Robert G. 1988. Ecogeographic analysis. USDA Forest Service Misc Publication 1465. USDA Forest Service, Washington, DC. 16 pp.

Ecological units of different sizes for predictive modeling of resource productivity and ecological response to management need to be identified and mapped. A set of criteria for subdividing a landscape into ecosystem units of different sizes is presented, based on differences in factors important in differentiating ecosystems at varying scales in a hierarchy. Practical applications of such units are discussed.

The prospect of increased land development in the Lake Tahoe basin emphasizes the need for better criteria for planning and executing development. Land capability classes are established to guide regional planning and development. Land tolerance is used as the principal measure of capability. Two types of factors are used to rate capability or tolerance: soil type and geomorphic setting. The type and intensity of land use consistent with natural limitations are suggested for each capability class. Limits on land-surface modification are expressed as a percentage of each area that can be used for impervious cover.

Working Papers

  • Bailey, Robert G. 2006. Ecoregion mapping and boundaries. Briefing paper prepared for a workshop to revise Army Regulation 70-38: Research, Development, Test and Evaluation of Material for Worldwide Military Operational Environments, Yuma Proving Ground, AZ, January 30-February 2.

Ecoregion maps show the earth's surface subdivided into identifiable areas based on macroscale patters of ecosystems. These ecoregions delimit large areas within which local ecosystems recur more of less throughout the region in a predictable pattern. This presentation summarizes the rationale used in identifying ecoregion boundaries on maps of the United States, North America, and the world's continents.

  • Bailey, Robert G. 2006. Ecoregions of the Rocky Mountain Research Station. Briefing paper prepared for a workshop to revise Army Regulation 70-38: Research, Development, Test and Evaluation of Material for Worldwide Military Operational Environments, Yuma Proving Ground, AZ, January 30-February 2.

This paper explains, describes, and displays the ecosystem-based regions of the Rocky Mountain Research Station. Ecoregions are identified at three hierarchical levels of detail—domain, division, and province—based primarily on climatic conditions and on the prevailing plant formations determined by those conditions. The third level may include additional criteria, for instance altitude variation within climate types. These regions are based on an explicit approach in which regions are differentiated on the basis of comparable likeness and differences.

This article addresses patterns of ecosystems within a region and what these patterns signify in terms of the processes that create them, and it goes on to explain their relevance to design of sustainable landscapes. Until recently, few landscape designers have explored the underpinnings of regional landscape design. Understanding the pattern of sites and the processes that shape them provides design inspiration for urban and suburban landscapes that are in harmony with the region they are embedded within.

The Forest Service has developed a mapping framework to help managers better understand the hierarchical order of the ecosystems they manage, the National Hierarchical Framework of Ecological Units. Broad-scale ecoregions (domain, division, and province) and subregions (sections) have been mapped. A team has been working to complete the hierarchy by identifying subsections. This paper presents an evaluation of this idea and gives recommendations.

A map showing the upper four levels of Ecomap down to the section level has been published for the entire United States, based on macroclimatic conditions and plant formations. Within the same macroclimate, broad-scale landforms break up the climatic pattern that would occur otherwise and provide a basis for further differentiation of mesoscale ecosystems, known as landscape mosaics. This paper suggests how different levels of landform differentiation could be correlated with landscape mosaics at different levels of resolution.

A map showing the upper four levels of Ecomap down to the section level has been published for the entire United States. A national team is working to complete a map of the fifth level, termed subsection. The resulting subsection map appears problematic both in terms of the underlying rationale and in terms of conflict with preexisting maps of the upper levels of Ecomap. An alternative route is suggested that builds on existing approaches used to delineate sections on the published map.

Information about climate is fundamental to an assessment of the land’s capability and suitability for various kinds of use. Areas of uniform climate are also used to identify ecosystem units because climate acts as the primary input of energy and moisture into the system. As the climate changes, the kinds and patterns of dominant life forms of plants and animals change, as do the kinds of soils. Ecosystems of different climates differ significantly.

Presentations

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A new map of Military Operating Environments (MOE) was developed from a world-wide ecoregional classification system that is based on climatic conditions and the prevailing vegetation determined by those conditions. This map allows for identification of operational environments across the globe that are analogous to those U.S. Army installations where training and testing of soldiers and equipment take place. Forty major U.S. Army installations were described by their MOE classification. It was determined that there are numerous installations that reside in hot continental and subtropical climates, as well as tropical/subtropical and temperate deserts. There is significant lack of adequate training and testing land resources in the Mediterranean, savanna, and rainforest environments.

Criteria for delineating ecosystems on a scale-related basis are presented, based on the processes that operate from the regional scale (ecoregion) to the local, site scale. The units derived from this approach are termed genetic, in that they are predicated upon an understanding of the causal processes that control the pattern of ecosystems. Appreciating spatial relationships between causal mechanisms and resultant patterns is a key to understanding ecosystem dynamics and how they respond to management.

This presentation discusses the origins of ecosystem patterns from ecoregion to local scale. It describes how understanding these patterns can help scientists and managers in two ways. First, the local systems are shown within context of larger systems. This perspective can be applied in assessing the connections between action at one scale and effect at another, the spatial transferability of models, and the links between terrestrial and aquatic systems. Second, they are given information about the geographic patterns in ecosystems. Consequently, they are in a better position to design sampling networks, transfer knowledge, and analyze ecosystem diversity. The approach illustrates an alternative to single-phenomena and single-scale approaches and indicates the trend toward integration of factors in classifying and analyzing ecosystems at multiple scales.

  • Bailey, Robert G. 2006. Marine ecoregions. Presentation slides. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.

Oceans occupy some 70 percent of the Earth's surface. Understanding continental systems requires a grasp of the enormous influence that marine systems exert on terrestrial climatic patterns and thus the character and distribution of continental ecoregions. The intent of this paper is to analyze factors affecting the distribution of the Earth’s major marine ecoregions. The objective is to go beyond empirical description by suggesting mechanisms that are responsible for producing the world pattern. Ecoregions recur in similar form in various parts of the world. Because of this predictability, we can transfer knowledge gained about one region to another.

The majority of American forest and grassland ecosystems are adapted to fire of varying frequencies and magnitudes. Fire-excluded systems are prone to changes in composition and density, and are susceptible to catastrophic fire and invasion by non-native species. Planning for fire and land management must incorporate an improved understanding of fire regimes. This paper discusses fire regimes of different ecosystems at the scale of ecoregion, and explores how understanding fire regimes at this scale can abate the threat of fire exclusion and restore fire-adapted ecosystems.

  • Bailey, Robert G. 2004. Ecogeographic analysis. Presentation slides. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.

This presentation outlines a system that subdivides the Earth into a hierarchy of increasingly finer-scale ecosystems. The system consists of a three-part, nested hierarchy of ecosystem units and associated mapping criteria. Delineating units involves identifying the environmental factors controlling the spatial geography of ecosystems. Macroscale units (ecoregions) are climatically controlled and delineated as Koppen-Trewartha climate zones. Nested within these are landscape mosaics, the mesoscale units, controlled by landform and delineated by Hammond's landform regions.

An ecoregion is a large area of similar climate where similar ecosystems occur on similar sites. This presentation describes the processes that shape local ecosystem patterns, and goes on to explore how understanding the patterns of a particular region is import for design of (1) sampling networks for monitoring ecosystems, and (2) sustainable landscape-scale management.

Contact Information

Contact Robert Bailey for additional information on ecoregions.

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