NatureServe ranks have been designated primarily for species and ecological communities in the United States and Canada, but the methodology is global, and has been used in some areas of Latin America and the Caribbean.
Most NatureServe ranks show the conservation status of a plant or animal species or a natural ecological community using a one-to-five numerical scale (from most vulnerable to most secure), applied either globally (world-wide or range-wide) or to the entity's status within a particular nation or a specified subnational unit within a nation.
NatureServe conservation statuses may be applied at any or all of three geographical levels: The most commonly encountered NatureServe conservation statuses at the G-, N-, or S-level are: Thus, for example, a G3 species is "globally vulnerable", and an N2 species is "nationally imperiled" for the particular country the rank is assigned.
Several less frequent special cases are addressed through other notation in the NatureServe ranking system, including: Note, however, that regionally native species or other taxa that have recently arrived in the area of interest by natural means (such as wind, floods, or birds), without direct or indirect human intervention, are ranked by the same methodology and notation as for other native taxa.
For example, many fertile polyploid species of ferns formed by interspecific hybridization followed by chromosome doubling.