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Species Conservation Rankings

The Saskatchewan Conservation Data Centre is responsible for evaluating and assigning a conservation rank to each taxon, resident or transient, found in the province. The process of conservation ranking involves the review of information housed in the SKCDC database as well as scientific and government literature, natural history publications, consultations with recognized experts and highly knowledgeable amateur naturalists as well as field work. The goal of this process is to arrive at a subnational or S-rank, based on the best available information, that best characterizes the extirpation risk of an element in the province. This subnational or S-rank serves to focus conservation concern.

Ranks are calculated using a standardized procedure set forth by NatureServe, which allows the SKCDC to follow a standardized, repeatable, and transparent procedure for categorizing the province’s flora and fauna.

Each species assessment takes into account not just rarity, but also trends and threats:

A minimum number of factors, and a minimum of certain types of factors, are needed to calculate a rank. The factors are scaled and weighted according to their impact on risk, and points are used to score the contribution of each factor to the risk. The final overall score is equated with a rank.

Interpreting Conservation Ranks

Ranks are given as the letter that represents the geographic scale followed by a number that represents the taxon’s risk of extirpation. A higher S-rank (e.g. S5) indicates that a species is more common, more stable, and less threatened than a species with a lower S-rank (e.g. S1), which would indicate that a species is rarer, declining, facing a high threat level, or a combination of these factors.

Species with a low S Rank are at a higher risk of extirpation.
Critically Imperiled/ Extremely rareAt very high risk of extinction or extirpation due to extreme rarity, very steep declines, high threat level, or other factors.
Imperiled/Very rareAt high risk of extinction or extirpation due to a very restricted range, very few populations, steep declines, threats or other factors.
Vulnerable/Rare to uncommonAt moderate risk of extinction or extirpation due to a restricted range, relatively few populations, recent and widespread declines,threats, or other factors.
Apparently SecureUncommon but not rare; some cause for long-term concern due to declines or other factors.
Secure/CommonDemonstrably secure under present conditions; widespread and abundant; low threat level.

A range rank (such as S3S4) is used when the taxon straddles the criteria for more than one rank (i.e. S3 and S4). Letters in the rank are referred to as modifiers and can have various meanings:

A - accidental or causal in the province, including species recorded infrequently that are far outside their range (birds and butterflies)
Bfor a migratory species, applies to the breeding population in the province
Nfor a migratory species, applies to the non-breeding population in the province
Mfor a migratory species, rank applies to the transient (migrant) population
Hhistorical occurrence of the taxon, without recent verification (e.g. 20-40 years or older)
Ustatus is uncertain in Saskatchewan because of limited or conflicting information (unrankable)
Xbelieved to be extinct or extirpated from the province
NRrank is not yet assigned or species has not yet been assessed (not ranked)
NAconservation status is not applicable to the species (e.g. it may have been determined to have been introduced in Saskatchewan)

A “?” following a rank means that there is some uncertainty associated with it. For example, a rank of S3? means that it is believed to be most likely an S3, but there is a significant chance that it could be an S2 or S4.

The SKCDC prioritizes taxa for ranking based on a five-year rotation. Information on each taxon is gathered and compiled prior to assessing the rank factors. Once a rank is calculated, it is reviewed by SKCDC staff and other experts (e.g., members of the Botanical Assessment Working Group for plants), and can be adjusted if the reviewers feel that it is necessary. The ranks are only as good as the information that is put into the calculator , so it is very important for the SKCDC to have all of the most up-to-date information on a taxon before ranking it. External data may play a role in adjusting the rank, but if at all possible, the SKCDC will incorporate such data into its database prior to the rank calculation.

Where data is scarce, the SKCDC may rely on expert opinion to inform a conservation rank.

Why are these ranks important? Conservation activities are focused on taxa that have a rank of S1, S2 or S3, and avoidance or mitigation is required for these taxa during any development projects. Taxa with a rank including S3 or less are tracked by the SKCDC and locations of conservation significance are mapped. Taxa that are not ranked S1, S2 or S3 may still be tracked if special circumstances warrant.

Accessing Species Conservation Rankings
Species conservation rankings (S-Ranks) can be found in any of the SKCDC's species lists.
Related Resources:
Conservation Status Assessment: Identifying Threatened Species and Ecosystems - An overview of methods at
NatureServe Conservation Status Assessments: Methodology for Assigning Ranks - NatureServe Report
NatureServe Conservation Status Assessments: Factors for Evaluating Species and Ecosystem Risk - NatureServe Report