Porsild's bryum (Haplodontium macrocarpum) COSEWIC assessment and status report: chapter 11

Summary of Status Report

Porsild’s bryum is a highly disjunct (fragmented populations), globally rare, moss that is known from 26 sites in North America, and restricted to 10 locations in Canada. The Canadian localities are restricted to five general areas. The species grows in mainly mountainous areas on wet cliffs characterized by calcareous substrate, presence of constant seepage and winter desiccation. Species presence is limited by habitat availability, dispersal and poor establishment ability; population survival is limited by cliff stability. Direct threats to populations include natural or anthropogenic events that destabilize the rock cliff habitat. Several populations have declined from their prior population sizes including populations in Alberta that suffered desiccation damage during the winter of 2001-2002 and a Newfoundland population that was nearly extirpated by ice scouring and rock fall in the same winter season. Imminent threats are coal mine and road development to some Alberta populations.

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