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Understanding Ranks

Sub-national (provincial) ranks (S-ranks)

Conservation Data Centres and NatureServe use existing information and expertise, for ranking species rarity or conservation status. Ranks help them identify gaps in knowledge for species for which element occurrence data are maintained; typically information is maintained for species ranked critically imperiled (S1) to vulnerable (S3) in given jurisdictions. Individual CDCs are responsible for developing sub-national ranks for their area. The AC CDC works with provincial and federal experts to develop rarity ranks for species in each of the following provinces: New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland & Labrador. Factors considered when ranking include: number of element occurrences, distribution, population size, abundance trends, and threats.

Sub-national element rank definitions

The following definitions refer to species and community ranks at sub-national (provincial) levels. Sub-national ranks are specific to a province. Therefore, a species that is common (S4) in New Brunswick, could be ranked as extremely rare (S1) in Prince Edward Island.

S-rank Definition
SX Presumed Extirpated - Species or community is believed to be extirpated from the province. Not located despite intensive searches of historical sites and other appropriate habitat, and virtually no likelihood that it will be rediscovered.
S1 Critically Imperiled - Critically imperiled in the province because of extreme rarity (often 5 or fewer occurrences) or because of some factor(s) such as very steep declines making it especially vulnerable to extirpation from the province.
S2 Imperiled - Imperiled in the province because of rarity due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors making it very vulnerable to extirpation from the province.
S3 Vulnerable - Vulnerable in the province due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation.
S4 Apparently Secure - Uncommon but not rare; some cause for long-term concern due to declines or other factors.
S5 Secure - Common, widespread, and abundant in the province.
SNR Unranked - Provincial conservation status not yet assessed.
SU Unrankable - Currently unrankable due to lack of information or due to substantially conflicting information about status or trends.
SNA Not Applicable - A conservation status rank is not applicable because the species is not a suitable target for conservation activities.
S#S# Range Rank - A numeric range rank (e.g., S2S3) is used to indicate any range of uncertainty about the status of the species or community. Ranges cannot skip more than one rank (e.g., SU is used rather than S1S4).
SH Possibly Extirpated (Historical)—Species or community occurred historically in the province, and there is some possibility that it may be rediscovered. Its presence may not have been verified in the past 20-40 years. A species or community could become SH without such a 20-40 year delay if the only known occurrences in a province were destroyed or if it had been extensively and unsuccessfully looked for. The SH rank is reserved for species or communities for which some effort has been made to relocate occurrences, rather than simply using this status for all elements not known from verified extant occurrences.
Not Provided Species is not known to occur in the province.

Breeding Status Qualifiers

Qualifier Definition
B Breeding - Conservation status refers to the breeding population of the species in the province.
N Nonbreeding - Conservation status refers to the non-breeding population of the species in the 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 province.

Note: A breeding status is only used for species that have distinct breeding and/or non-breeding populations in the province. A breeding-status S-rank can be coupled with its complementary non-breeding-status S-rank if the species also winters in the province, and/or a migrant-status S-rank if the species occurs regularly on migration at particular staging areas or concentration spots where the species might warrant conservation attention. The two (or rarely, three) status ranks are separated by a comma (e.g., "S2B, S3N" or "SHN, S4B, S1M").

Other Qualifiers

Qualifier Definition
? Inexact or Uncertain - Denotes inexact or uncertain numeric rank. (The ? qualifies the character immediately preceding it in the S-rank.)

National and Global Ranks

Information supporting S-ranks in turn supports broader-scale ranking, national (N-rank) and global (G-rank). Canadian CDCs, from the Atlantic to British Columbia, help develop and update N-ranks for Canadian plants and animals. Although many believe that National ranks offer great value, there is increasing interest in categories used by COSEWIC and General Status Assessments, outlined briefly below. Global ranks are assigned by staff specialists at NatureServe in consultation with CDC specialists and other science experts. Global rank definitions are similar to sub-national rank definitions but they refer to the entire range for species or communities regardless of national boarders. For instance, G1 – Critically Imperiled – extremely rare and extremely vulnerable to extinction due to natural or human causes (5 or fewer global occurrences or less than 1000 individuals), while G5 – Demonstrably secure. See the NatureServe explorer for additional details.

COSEWIC and General Status of Wild Species

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) uses: extinct, extirpated, endangered, threatened, vulnerable, special concern, insufficient information, and secure to describe the status of species (but not communities) in Canada. The General Status of Wild Species in Canada, uses a ranking system similar to that used by NatureServe and all CDCs. (See Wild Species: The General Status of Species in Canada – for additional details).