Rare species

[Eric or Pat Metzler]

Scott:

In answer to your question: "Why reinvent the wheel?" the same confusion
about the word rare is rampant in these definitions.  Rarity can not be
equated with peril, and the TNC system consistently confuses the two
terms.  I'm a strong advocate of TNC, but their system needs lots of
improvement.

Thanks for bringing this into the conversation.  It further illustrates
the problem.

Cheers,

Eric

Annette & Scott Ranger wrote:
>
> 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