Conservation ranks are assigned to species and communities so that at-risk elements can be prioritized for conservation efforts. The international network of Natural Heritage Programs employs a standardized ranking system to denote global (G -- range-wide) and state status (S) (NatureServe 2003). Ranks range from 1 (critically imperiled) to 5 (demonstrably secure), reflecting the relative degree to which they are “at-risk”. Rank definitions are given below along with rank qualifiers. A number of factors are considered in assigning ranks -- the number, size and distribution of known occurrences, and the threat to their integrity or existence. For more information see NatureServe Explorer Conservation Status Ranks.

For example, Baltic rush (Juncus balticus) Herbaceous Vegetation is ranked G5 S5, common, abundant and not vulnerable throughout both its range in Montana and elsewhere. It occurs in every western state except Arizona.

Global and State Ranks
G1 S1	At high risk because of extremely limited and/or rapidly declining numbers or range, making it highly vulnerable to global extinction or extirpation in the state.
G2 S2	At risk because of very limited and/or declining numbers, range, and/or habitat, making it vulnerable to global extinction or extirpation in the state.
G3 S3	Potentially at risk because of limited and/or declining numbers, range, and/or habitat, even though it may be abundant in some areas.
G4 S4	Uncommon but not rare (although it may be rare in parts of its range), and usually widespread. Apparently not vulnerable in most of its range, but possibly cause for long-term concern.
G5 S5	Common, widespread, and abundant (although it may be rare in parts of its range). Not vulnerable in most of its range.