This dataset represents an aggregated measure of crucial habitat for species and habitats of interest to the western states' fish and wildlife management agencies. Crucial habitat describes places that are expected to contain the resources necessary for continued health of fish and wildlife populations or important ecological systems expected to provide high value for a diversity of fish and wildlife. Specifically, crucial habitat for fish and wildlife was defined to include several data types and layers of information available to states:

* Habitat for Species of Concern: terrestrial and/or aquatic

* Native and Unfragmented Habitat: may include landscape condition, large natural areas, natural vegetation communities, ecological systems of concern, landscape corridors, and/or freshwater integrity

* Riparian and wetland habitat

* Connectivity or linkage areas: wildlife corridors

* Quality habitat for species of importance not already accounted for in "Habitat for SOC"

States compiled data encompassing all of the above categories and then ranked areas as "crucial habitat" using a relative, six-level prioritization scheme, where 1 represents areas "most crucial," or those areas that most closely meet the definition of crucial habitat and 6 represents "least crucial" areas, or those areas that least closely meet the definition of crucial habitat based on mutually agreed upon definitions. Rankings of zero (0) represent no data. Crucial habitat values are in no way regulatory and do not imply specific avoidance or mitigation measures for a given area. Crucial habitat values should be interpreted as the relative probability, or risk, that a high-priority species or habitat would be encountered in a given area based on the best available scientific information.