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NatureServe Conservation Status

NatureServe scientists assign each species a global rank (called a G-rank), which applies across its entire range. NatureServe scientists work with local Conservation Data Centers to assign a national rank (N-rank) for nations of interest in the species range, and a subnational rank (S-rank) for states, province, or other subnational jurisdictions of interest in its range (e.g. Sonora state in Mexico). NatureServe scientists receive guidance from experts and the local Conservation Data Centers on particular taxonomic groups. New information provided by field surveys, monitoring activities, consultation, and literature review, improves accuracy and keeps ranks current.

Interpreting NatureServe Conservation Status Ranks

GX

Presumed Extinct (species )— Not located despite intensive searches and virtually no likelihood of rediscovery.

Eliminated (ecological communities )—Eliminated throughout its range, with no restoration potential due to extinction of dominant or characteristic species.

GH

Possibly Extinct (species )— Missing; known from only historical occurrences but still some hope of rediscovery.

Presumed Eliminated (Historic, ecological communities )—Presumed eliminated throughout its range, with no or virtually no likelihood that it will be rediscovered, but with the potential for restoration, for example, American Chestnut Forest.

G1

Critically Imperiled — At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors.

G2

Imperiled — At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.

G3

Vulnerable — At moderate risk of extinction due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors.

G4

Apparently Secure — Uncommon but not rare; some cause for long-term concern due to declines or other factors.

G5

Secure — Common; widespread and abundant.


Variant Ranks

Rank

Definition

G#G#

Range Rank —A numeric range rank (e.g., G2G3) is used to indicate the range of uncertainty in the status of a species or community. Ranges cannot skip more than one rank (e.g., GU should be used rather than G1G4).

GU

Unrankable —-Currently unrankable due to lack of information or due to substantially conflicting information about status or trends. Whenever possible, the most likely rank is assigned and the question mark qualifier is added (e.g., G2?) to express uncertainty, or a range rank (e.g., G2G3) is used to delineate the limits (range) of uncertainty.

GNR

Unranked —Global rank not yet assessed.

GNA

Not Applicable —A conservation status rank is not applicable because the species is not a suitable target for conservation activities.

 

Rank Qualifiers

Qualifier

Definition

?

Inexact Numeric Rank —Denotes inexact numeric rank (e.g., G2?)

Q

Questionable taxonomy —Taxonomic distinctiveness of this entity at the current level is questionable; resolution of this uncertainty may result in change from a species to a subspecies or hybrid, or the inclusion of this taxon in another taxon, with the resulting taxon having a lower-priority conservation priority.

C

Captive or Cultivated Only — At present extant only in captivity or cultivation, or as a reintroduced population not yet established.


Assessment Criteria

Use of standard ranking criteria and definitions makes NatureServe status comparable across taxonomic groups-thus G1 has the same basic meaning whether applied to a salamander, a peccary, or a forest community. Standardization also makes statuses comparable across jurisdictions, which in turn allows NatureServe scientists to use the national and subnational status assigned by local Conservation Data Centers to determine and refine or reaffirm global status. Ranking is a qualitative process: it takes into account several factors which function as guidelines rather than arithmetic rules. The ranker's overall knowledge of the element allows him or her to weigh each factor in relation to the others and to consider all pertinent information for a particular element. The following factors are important in assigning a status:

  • total number and condition of element occurrences
  • population size, range extent, and area of occupancy
  • short and long-term trends in the foregoing factors
  • threats
  • environmental specificity
  • fragility

Logo for NatureServe Copyright 2007
NatureServe
Version 5.0 (10 April 2007)
Data last updated: April 2007