Knowing about the area you are exploring helps you focus on the things (plants, animals and even rocks) you are most likely to find there.  One way scientists have been organizing areas uses the concept of the ecoregion.  An ecoregion is an ecologically and geographically defined area that covers a relatively large area of land or water, and contains characteristic, geographically distinct assemblages of natural communities and species.   Or, more simply, ecoregions are large areas of similar climate where ecosystems recur in predictable patterns.

Defining Ecoregions

To define the boundaries of ecoregions,  scientists take a large land mass, say the United States, and divide it into contiguous areas that are internally similar, while being different from the areas that surround them.  The results depend upon the factors that are considered in their development and those factors are, in turn, based upon the specific purpose of creating the ecoregion boundary.

The Environmental Protection Agency and the U.S. Forest Service got together and defined ecoregions in three layers:



Primarily based upon weather,  there are three domains in the continental U.S. – dry, humid temperate and humid tropical as illustrated below.

U.S. Ecosystem Domains



Divisions take into account more specific climactic conditions.  Categories include warm continental, hot continental, subtropical, prairie, temperate steppe and so on.  As you can surmise, these smaller divisions begin to get more closely associate with particular plant communities that can survive under these climate conditions.   Division boundaries are shown on the following map.  Note that the domain boundaries remain and the divisions separate them into smaller components.




Provinces further separate the divisions based upon broad vegetative types found across the U.S. “Broad” includes vegetation defined as, for example,  eastern hardwoods, prairie parkland, Colorado plateau, California dry steppe, and so on.  The following map shows the ecosystem provinces overlain on the divisions:




Once the provinces are applied to the divisions we have the ecoregion map.  The above map is the result.  The map below shows the ecoregions and how they relate to the states:

Ecoregion of the United States

Using the Ecoregions

Ecoregions are obviously a concept developed for a purpose.  The primary purpose is to help us understand how  ecosystems differ and function in different ways.  They also offer a great way to organize material in an appropriate context.  For example,  here in Oregon the state uses ecoregions as a basis for the Oregon Conservation Strategy.  Oregon modifies the ecoregions slightly (see below) then organizes key habitats (Strategy Habitats) and key species (Strategy Species) with ecoregions.  Since all of the Oregon information is on the web (, you can use it too.  It just becomes a matter of learning about the ecoregion you are exploring including its habitats and key species.  With that knowledge you start your explorations well ahead those that have not done this research.

Oregon Ecoregions

Other states may have similar websites that can help you get information from other places.  Ecoregions have also been developed worldwide, so other nations may be using them.  A Google search should help you find and learn about your favorite ecoregion.

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