Definitions of NatureServe Conservation Status Ranks

Note that the term occurrences in these definitions refers specifically to Element Occurrences. Also, where no distinction is made, a definition is identical for species and ecological communities.

NatureServe Global Conservation Status Definitions

Listed below are definitions for interpreting NatureServe’s global (range-wide) conservation status ranks. Global conservation status ranks are assigned by NatureServe scientists or by a designated lead office in the NatureServe network.

Global (G) Conservation Status Ranks

 

RANK DEFINITION
GX

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

Presumed Eliminated(ecosystems, i.e., ecological communities and systems) — Eliminated throughout its range, due to loss of key dominant and characteristic taxa and/or elimination of the sites and ecological processes on which the type depends.

GH Possibly Extinct (species) or Possibly Eliminated (ecosystems) — Known from only historical occurrences but still some hope of rediscovery. Examples of evidence include (1) that a species has not been documented in approximately 20-40 years despite some searching and/or some evidence of significant habitat loss or degradation; (2) that a species or ecosystem has been searched for unsuccessfully, but not thoroughly enough to presume that it is extinct or eliminated throughout its range.
G1 Critically Imperiled — At very high risk of extinction or elimination due to very restricted range, very few populations or occurrences, very steep declines, very severe threats, or other factors.
G2 Imperiled — At high risk of extinction or elimination due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors.
G3 Vulnerable — At moderate risk of extinction or elimination due to a fairly restricted range, relatively few populations or occurrences, recent and widespread declines, threats, or other factors.
G4 Apparently Secure — At fairly low risk of extinction or elimination due to an extensive range and/or many populations or occurrences, but with possible cause for some concern as a result of local recent declines, threats, or other factors.
G5 Secure — At very low risk or extinction or elimination due toi a very extensive range, abundant populations or occurrences, and little to no concern from declines or threats.
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Variant Global Conservation Status Ranks

 

RANK DEFINITION
G#G# Range Rank — A numeric range rank (e.g., G2G3, G1G3) is used to indicate uncertainty about the exact status of a taxon or ecosystem type. Ranges cannot skip more than two ranks (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. NOTE: Whenever possible (when the range of uncertainty is three consecutive ranks or less), a range rank (e.g., G2G3) should be 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 or ecosystem is not a suitable target for conservation activities. A global conservation status rank may be not applicable for several reasons, related to its relevance as a conservation target. For species, typically the species is a hybrid without conservation value, or of domestic origin. For ecosystems, the type is typically non-native (e.g, many ruderal vegetation types), agricultural (e.g. pasture, orchard) or developed (e.g. lawn, garden, golf course).
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Global Rank Qualifiers

RANK DEFINITION
? Inexact Numeric Rank - Denotes inexact numeric rank; this should not be used with any of the Variant Global Conservation Status Ranks or GX or GH.
Q Questionable taxonomy that may reduce conservation priority - Distinctiveness of this entity as a taxon or ecosystem type at the current level is questionable; resolution of this uncertainty may result in change from a species to a subspecies or hybrid, or inclusion of this taxon or type in another taxon or type, with the resulting taxon having a lower-priority (numerically higher) conservation status rank. The “Q” modifier is only used at a global level and not at a national or subnational level.
C Captive or Cultivated Only - Taxon or ecosystem at present is presumed or possibly extinct or eliminated in the wild across their entire native range but is extant in cultivation, in captivity, as a naturalized population (or populations) outside their native range, or as a reintroduced population or ecosystem restoration, not yet established. The "C" modifier is only used at a global level and not at a national or subnational level. Possible ranks are GXC or GHC. This is equivalent to "Extinct in the Wild (EW) in IUCN’s Red List terminology (IUCN 2001).

For more detail, see Conservation Status Rank Qualifiers.

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Infraspecific Taxon Global Conservation Status Ranks

Infraspecific taxon status ranks apply to species only; these ranks do not apply to ecological communities or systems.

RANK DEFINITION
T# Infraspecific Taxon (trinomial) - The status of infraspecific taxa (subspecies or varieties) are indicated by a "T-rank" following the species’ global rank. Rules for assigning T-ranks follow the same principles outlined above. For example, the global rank of a critically imperiled subspecies of an otherwise widespread and common species would be G5T1. A T subrank cannot imply the subspecies or variety is more abundant than the species, for example, a G1T2 subrank should not occur. A vertebrate animal population (e.g., listed under the U.S. Endangered Species Act or assigned candidate status) may be tracked as an infraspecific taxon and given a T rank; in such cases a Q is used after the T-rank to denote the taxon’s informal taxonomic status.
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NatureServe National and Subnational Conservation Status Definitions

Listed below are definitions for interpreting NatureServe conservation status ranks at the national (N-rank) and subnational (S-rank) levels. The term "subnational" refers to state or province-level jurisdictions (e.g., California, Ontario).

Assigning national and subnational conservation status ranks for species and ecosystems (ecological communities, vegetation types, and systemss) follows the same general principles as used in assigning global status ranks. Historically, a subnational rank, however, could not imply that a species or ecosystem is more secure at the state/province level than it is nationally or globally (e.g., a rank of G1S3 is invalid), and similarly, a national rank could not exceed the global rank. But see below (“Global and State Ranking System”) for rare exception to this rule, because of the weight now given to Threats and Trends.. Subnational ranks are assigned and maintained by state or provincial NatureServe network programs.

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National (N) and Subnational (S) Conservation Status Ranks

RANK DEFINITION

NX

SX

Presumed Extirpated—Species or ecosystem is believed to be extirpated from the jurisdiction (i.e., nation, or state/province). Not located despite intensive searches of historical sites and other appropriate habitat, and virtually no likelihood that it will be rediscovered. [equivalent to “Regionally Extinct” in IUCN Red List terminology]

 

NH

SH

Possibly Extirpated – Known from only historical records but still some hope of rediscovery. There is evidence that the species or ecosystem may no longer be present in the jurisdiction, but not enough to state this with certainty. Examples of such evidence include (1) that a species has not been documented in approximately 20-40 years despite some searching and/or some evidence of significant habitat loss or degradation; (2) that a species or ecosystem has been searched for unsuccessfully, but not thoroughly enough to presume that it is no longer present in the jurisdiction.

N1

S1

Critically Imperiled At very high risk of extirpation in the jurisdiction due to very restricted range, very few populations or occurrences, very steep declines, severe threats, or other factors.

N2

S2

Imperiled

— At high risk of extirpation in the jurisdiction due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors.

N3

S3

Vulnerable

— At moderate risk of extirpation in the jurisdiction due to a fairly restricted range, relatively few populations or occurrences, recent and widespread declines, threats, or other factors.

N4

S4

Apparently Secure

— At a fairly low risk of extirpation in the jurisdiction due to an extensive range and/or many populations or occurrences, but with possible cause for some concern as a result of local recent declines, threats, or other factors.

N5

S5

Secure

— At very low or no risk of extirpation in the jurisdiction due to a very extensive range, abundant populations or occurrences, with little to no concern from declines or threats.
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Variant National and Subnational Conservation Status Ranks

 

RANK DEFINITION
N#N#

S#S#

Range Rank —A numeric range rank (e.g., S2S3 or S1S3) is used to indicate any range of uncertainty about the status of the species or ecosystem. Ranges cannot skip more than two ranks (e.g., SU is used rather than S1S4).
NU

SU

Unrankable —Currently unrankable due to lack of information or due to substantially conflicting information about status or trends.
NNR

SNR

Unranked — National or subnational conservation status not yet assessed.
NNA

SNA

Not Applicable A conservation status rank is not applicable because the species or ecosystem is not a suitable target for conservation activities (e.g., long distance aerial and aquatic migrants, hybrids without conservation value, and non-native species or ecosystems (see Master et al. 2012, Appendix A, pg 70 for further details). Note: When the Element Global Rank is GNA, the Element National Rank should be entered as NNA and Element Subnation Rank should be entered as SNA for all national and subnational records associated with it.
Not Provided Species or ecosystem is known to occur in this nation or state/province. Contact the appropriate NatureServe network program for assignment of conservation status.
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National and Subnational Rank Qualifiers

RANK DEFINITION
N#?

S#?

Inexact Numeric Rank—Denotes inexact numeric rank; this should not be used with any of the Variant National or Subnational Conservation Status Ranks, or NX, SX, NH, or SH.
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Breeding Status Qualifiers

 

QUALIFIER EFINITION

B

Breeding—Conservation status refers to the breeding population of the species in the nation or state/province.
N Non-breeding—Conservation status refers to the non-breeding population of the species in the nation or state/province.
M Migrant—Migrant species occurring regularly on migration at particular staging areas or concentration spots where the species might warrant conservation attention. Conservation status refers to the aggregating transient population of the species in the nation or state/province.

For more detail, see Conservation Status Rank Qualifiers.

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Global and State Ranking System

The primary tool used to develop priorities for individual species is the global and state ranking system used by NatureServe and its member Natural Heritage programs. The ranking system facilitates a quick assessment of a species’ rarity. Each species is assigned both a global (G) and state (S) rank on a scale of 1 to 5. The global ranks are assigned through a collaborative process involving both NatureServe and individual Natural Heritage Program scientists. State ranks are assigned by scientists within the Natural Heritage Program, who collaborate with other scientists and knowledgeable individuals.

A rank of G1 indicates critical imperilment on a global basis; the species is at great risk of extinction. S1 indicates critical imperilment within a particular state (in our case, Washington), regardless of its status elsewhere. A number of factors, such as the total population size, the number of occurrences, threats, etc., contribute to the assignment of global and state ranks. The information supporting these ranks is developed and maintained by the Natural Heritage Program and NatureServe.

The table below shows the matrix of possible combinations of global and state ranks. Note that some combinations are almost never possible; namely that a feature cannot be more common in the state than it is for the entire planet. However, there are cases where a trend factor (e.g. change in area of an ecosystem, or population size of a species) is relatively stable in a jurisdiction, but is strongly declining across most other parts of the range, and this could generate the asterisked values shown in the table.

GLOBAL AND STATE RANKING MATRIX
  S1 S2 S3 S4 S5
G1 G1S1 *      
G2 G2S1 G2S2 *    
G3 G3S1 G3S2 G3S3 *  
G4 G4S1 G4S2 G4S3 G4S4 *
G5 G5S1 G5S2 G5S3 G5S4 G5S5

* There are rare cases where the state rank may be lower than global rank (i.e., G1S2).

See text for explanation.

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See also:

Conservation Status Rank Qualifiers

NatureServe Conservation Status Assessments: Factors for Evaluating Species and Ecosystem Risk

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