Porsild's bryum (Haplodontium macrocarpum) COSEWIC assessment and status report: chapter 12
Technical Summary
Mielichhoferia macrocarpa (Bryum porsildii)
Porsild’s Bryum – Bryum de Porsild
Range of Occurrence in Canada:
AB, BC, NL, NU
Extent and Area Information
Extent of occurrence (EO) (km²)
> 1,000,000 km²
Specify trend in EO :
Stable
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
<< 1 km²
Specify trend in AO:
Unknown
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations :
10
Specify trend in number of locations:
Increase? (3 new discovered in 2002)
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat :
Unknown
Population Information
Generation time (average age of parents in the population) :
Unknown
Number of mature individuals :
1005+/- colonies
Total population trend: Decreasing (ca 15 % in 3 years)
Net loss of ~179 colonies (see Notes below)
% decline over the last/next 10 years or 3 generations.
n/a
Are there extreme fluctuations in number of mature individuals?
No
Is the total population severely fragmented?
Yes - 10 locations in five widely separated regions: Alberta, BC, NF, NU
Specify trend in number of populations.
Decline. 6 new populations at 3 locations discovered in 2002 but overall decline in number of colonies
Are there extreme fluctuations in number of populations?
No
List populations with number of mature individuals in each:
See Appendix 1
Threats (actual or imminent threats to populations or habitats)
In Alberta, Cadomin area, the cliff sites are very vulnerable to changes in upstream hydrology such as siltation of streams caused by excessive off-road vehicle use in headwaters. In this area outside the Wildland Park, coal mining exploration (planned Cheviot Mine) and road development have also threatened populations, notably the population called Mmac1, which is the largest contiguous population of the species in Canada and the largest in Alberta (Appendix 1). Road construction and blasting could cause large pieces of the intrinsically unstable rock to fall from cliff habitats taking Mielichhoferia macrocarpa colonies with them. British Columbia population potentially threatened by tourist activities.
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
S1 (Montana, NatureServe Explorer 2003)
Is immigration known or possible?
Not known. Possible but not probable
Would immigrants be adapted to survive in Canada?
Yes
Is there sufficient habitat for immigrants in Canada?
Yes
Is rescue from outside populations likely?
No
Quantitative Analysis
n/a
Notes - Population trends assessed as follows
Losses:
- “several hundred” colonies lost at Straitsview : 200 (estimate)
- 10-25% of area at Mmac2 (pers comm with author) : 0.25* 58 = 14 colonies
- 10-25% of area at Mmac3 (pers comm with author) : 0.25* 260 = 65 colonies
- < 10% of area at Mmac1 (pers comm with author) : 0.10* 177 = 17 colonies
Total Losses : ~ 296 colonies
Gains:
- Mt Socrates : 18 colonies
- Noddy Bay : 13+ colonies
- White Cape : 86+ colonies
Total Gain : 117+ colonies
Net Loss: 179 colonies
Current Status
G2 (global, NatureServe Explorer 2003)
Status and Reasons for Designation
Status: Threatened
Alpha-numeric code: Met criteria for Endangered, C2a(i), but was designated Threatened, B2ab(ii,iii,v); C2a(i); D1, because the species is not at imminent risk of extirpation.
Reasons for Designation: A rare moss with a severely fragmented distribution of 10 confirmed locations in Canada restricted to 5 general areas. The species grows in mainly mountainous areas on wet calcareous cliffs, presence of constant seepage and winter desiccation. Direct threats to populations include natural and human-caused events that destabilize the rock cliff habitat. There has been a recent a decline in habitat quality at the two most abundant locations and substantial loss of mature individual plants at one of these. Only one locality is protected. There is uncertainty about the status of northern Canadian populations.
Applicability of Criteria
Criterion A (Declining Total Population): Not applicable – does not meet decline not thresholds.
Criterion B (Small Distribution, and Decline or Fluctuation): Threatened under B2a and b (severely fragmented (fewer than 11 locations, continuing decline in extent of occupancy, quality of habitat, and number of mature individuals).
Criterion C (Small Total Population Size and Decline): Endangered under 2a(i), continuing decline under potential threat of mine development in Alberta, fragmented population with no population estimated > 250 mature individuals.
Criterion D (Very Small Population or Restricted Distribution): Threatened under D2 (AO <20 km2); also verges on criteria for Threatened D1 (< 1000 individuals).
Criterion E (Quantitative Analysis): Not applicable.
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