Foothill sedge (Carex tumulicola) COSEWIC assessment and status report: chapter 11

Technical Summary

Carex tumulicola

Foothill sedge – Carex tumulicole

Range of Occurrence in Canada:

SW British Columbia

Demographic Information

Generation time (average age of parents in the population) :

Perennial; unknown years

Population trend and dynamics

Observed percentage of reduction in total number of mature individuals over the last 10 years.

Unknown

Projected percentage of reduction in total number of mature individuals over the next 10 years.

Unknown

Observed percentage reduction in total number of mature individuals over any 10-year period, over a time period including both the past and the future.

Unknown

Are the causes of the decline clearly reversible?

No

Are the causes of the decline clearly understood?

Unknown

Are the causes of the decline clearly ceased?

No

Observed trend in number of populations :

Stable

Are there extreme fluctuations in number of mature individuals?

No

Are there extreme fluctuations in number of populations?

No

Number of mature individuals in each population

  • Population #1: 40-70 tussocks
  • Population #2: ~10 tussocks
  • Population #3: 1 tussock
  • Population #4: 50-100 tussocks
  • Population #5: 100-500 tussocks
  • Population #6: 50-200 tussocks
  • Population #7: 1 tussock
  • Population #8: 3 tussocks
  • Population #9: 280-460 tussocks
  • Population #10: 50-100 tussocks
  • Grand Total : 585–1,445

Extent and Area Information

Estimated extent of occurrence (km²) (Estimate is based on recent survey and data from BC Conservation Data Centre, and represents roughly the area of the triangle formed by Nanaimo, Oak Bay, and Metchosin) :

~1,700 km²

Observed trend in extent of occurrence. Increased search effort since first discovery has shown the EO to be much more extensive but trends are unknown :

Unknown

Are there extreme fluctuations in extent of occurrence?

No

Estimated area of occupancy (km²). Actual area occupied (100 ha) is an estimate based on authors’ tally of extent of habitat occupied by the 10 populations.

10 based on a 1x1 km square grid; 32 using a 2x2 grid km²

Observed trend in area of occupancy. As a consequence of search effort more sites are now known but these represent historically extant sites; actual trend in AO is unknown.

Unknown

Are there extreme fluctuations in area of occupancy?

No

Is the total population severely fragmented?

Yes

Number of current locations :

10

Trend in number of locations. Number of locations known has increased due to search effort but trend is unknown :

Unknown

Are there extreme fluctuations in number of locations?

No

Observed trend in quality of habitat :

Decline

Quantitative Analysis

 

Threats (actual or imminent, to populations or habitats)

Actual threats but with degree of impact uncertain

  1. Invasive species encroachment – all 10 pops
  2. Fire suppression – pops. 1, 2, 4-6, 9
  3. Habitat conversion (agriculture, urbanization, residential development) – pop. 7
  4. Off-road vehicles – pops. 1, 7
  5. Hydrologic alterations – pops. 1, 3, 7
  6. Trampling and mowing – pops. 1, 2, 3
  7. Loss of habitat due to bank slumping – subpop. 1m (due to wave action)

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA: apparently secure in WA, OR and CA; reported to occur in ID (S1), but this report likely erroneous

Is immigration known or possible?

Unknown

Would immigrants be adapted to survive in Canada?

Likely

Is there sufficient habitat for immigrants in Canada?

Yes

Is rescue from outside populations likely?

Unlikely

Current Status

COSEWIC: Endangered 2008

Status and Reasons for Designation

Status: Endangered

Alpha-numeric code: B1ab(iii)+2ab(iii)

Reasons for Designation: This perennial species is known from 10 localized and highly fragmented sites in southwestern British Columbiawhere it occurs in meadows and shrub thickets within Garry oak ecosystems, a critically imperiled habitat in Canada. The total Canadian population likely consists of fewer than 1000 mature individuals. Factors such as competition and habitat degradation from invasive alien plants, altered fire regimes, urbanization, trampling and mowing place the species at risk.

Applicability of Criteria

  • Criterion A (Decline in Total Number of Mature Individuals): Not applicable. No declines documented.
  • Criterion B (Small Distribution Range and Decline or Fluctuation): Endangered B1ab(iii)+2ab(iii). Meets criteria for EO and AO with the 10 populations being highly fragmented and decline in habitat quality is inferred based on a number of threats.
  • Criterion C (Small and Declining Number of Mature Individuals): Threatened C2a(i). The total population is <10,000 tussocks (plants) and no population is estimated to contain > 1,000 mature individuals
  • Criterion D (Very Small Population or Restricted Distribution): Threatened D1+2. Meets D1 since the actual population size is likely <1,000 mature plants, and meets D2 if the AO is based on a 1x1 km grid.
  • Criterion E (Quantitative Analysis): None available

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