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Provincial Ranking (B.C. Conservation Data Centre)
The status of a species is ranked (S-ranks) on a scale of one to five, and based on the number of extant occurrences of the species. Factors such as abundance, trends, range, protection and threats are also considered if the information is available. Species assigned as S1 or S2 are considered rare and endangered (Red-listed), while those assigned S3 are considered rare or uncommon (Blue-listed) (Cannings and Ptolemy 1998). 1. Critically imperiled because of extreme rarity (five or fewer extant occurrences, or very few remaining individuals) or because of some factors making it especially vulnerable to extirpation or extinction. 2. Imperiled because of rarity (typically 6-20 extant occurrences, or few remaining individuals) or because of some factors making it vulnerable to extirpation or extinction. 3. Rare or uncommon (typically 21-100 occurrences); may be susceptible to large-scale disturbances; e.g., may have lost extensive peripheral populations. 4. Frequent to common (more than 100 occurrences); apparently secure, but may have a restricted distribution; or there may be perceived threats. 5. Common to very common; demonstrably secure and essentially ineradicable under present conditions. X. Apparently extinct or extirpated, without the expectation that it will be rediscovered. E. Exotic or introduced species.
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