Abstract | This map layer shows Omernik's Level III ecoregions, derived from a
1:7,500,000 map created by J.M. Omernik in 1987 and from refinements of
Omernik's framework that were made for other projects. Ecoregions
describe areas of general similarity in ecosystems and in the type,
quality, and quantity of environmental resources. Omernik's ecoregions
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. Level III is the most detailed level available nationally for
this system of ecoregions. |