Rare species

[Annette & Scott Ranger]

I'm surprised no one has suggested The Nature Conservancy - Natural
Heritage Network ranking:

GLOBAL RANKS (denoted by G and number 1 to 5 or a letter code)

G1 Critically imperiled globally because of extreme rarity (typically
less than 6 occurrences, less than 1,000 individuals or very few
remaining acres) or because of some factor(s) making it especially
vulnerable to extinction.

G2  Imperiled globally because of extreme rarity (typically 6-20
occurrences, 1,000-3,000 individuals or few remaining acres) or because
of some factor(s) making it very vulnerable to extinction throughout its
range.

G3  Rare or uncommon (typically 21-100 occurrences or 3,000-10,000
individuals) throughout its range; or found locally, even abundantly, in
a restricted range (e.g., in a single state or physiographic region); or
vulnerable to extinction throughout its range because of specific
factors.

G4  Widespread, abundant and apparently secure globally, though it may
be quite rare in parts of its range, especially at the periphery
(typically 101 + occurrences & 10,000 + individuals); some cause for
long-term concern exists.

G5  Demonstrably secure, widespread and abundant globally; although it
may be quite rare in parts of its range, especially at the peripheries.

GH  Possibly extinct; of historical occurrence throughout its range,
i.e., formerly part of the established biota; still some hope of
rediscovery.

GX  Presumed extinct, with virtually no likelihood that it will be
rediscovered.

GU  Unrankable; possibly in peril, but status is uncertain.

HYB  Hybrid

SUBSPECIES RANKS (denoted by T and a number (1 to 5) or letter code)

T1-5  Same ranks as above, but applied after the G rank for subspecific
(trinomial) taxa (e.g., G5T2).

NATIONAL RANKS  (denoted by N and a number (1 to 5) or letter code)

N1-5  Same ranks as above, but applied to taxa based only on its
populations or occurrences within the borders of a nation.

NE  An exotic species established in the United States

NA  Accidental in the United States, part of established biota

STATE RANKS (denoted by S and a number (1 to 5) or letter code)

S1-5  Same ranks as above, but applied to taxa based only on its
populations or occurrences within the borders of a state.

SE  An exotic species established in the state

SA Accidental in the state, part of established biota

SR  Reported in state

SRF  Reported in state, but report was inaccurate (false)

SZ  Zero 'occurrences' (unreliably distributed in winter or during
migration)

SP  Potential; possibly in state, given known distribution in adjacent
states

MODIFIERS (added to a rank as additional information)

?   There is some doubt concerning status (e.g., G2?)

Q  Questionable taxonomy (e.g., G4Q)

N  Non-breeding (e.g., S1N)

B  Breeding (e.g., S1B)

C  Captive or cultivated only

Two G, T, N or S rankings together (G2G3, N4N5, T1T2, S3S5, etc.)
indicated uncertainty; the ranks given span the range of uncertainty.

This system has numerous advantages:
1. it is in widespread use in the U.S. by the state Natural Heritage
Programs and many federal agencies (like the U.S. Forest Service), and
by The Nature Conservacy in their international efforts.
2. it attempts in a simple, easy to understand manner, a quantification
of "rarity"
3. it addresses all the problems of just where a species is rare. A
plant can be G5S1, meaning it is demonstrably secure in its worldwide
distribution by critically imperiled in a given state
4. it allows for "honesty" in the communication of unsure information.

With all this going for it, why invent something else?

Scott Ranger