Cherry birch (Betula lenta) COSEWIC assessment and status report: chapter 13

Technical summary

Betula lenta
Cherry birch

bouleau flexible

Range of Occurrence in Canada: north shore of Niagara Peninsula, Ontario


Extent and area information

Extent of occurrence (EO) (km 2 ).
The shoreline area around the one known population where local dispersal is feasible.
2 km 2
Specify trend in EO.
No change
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km 2 ).
The one known population plus 2 adjacent recent historical sightings.
0.75 km 2
Specify trend in AO.
Recent decline
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations.
One
Specify trend in #.
Loss of 1-2 historical sites
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat.
Gradual decline in area over the last 1-2 generations due to loss or degradation of habitat


Population information

Generation time (average age of parents in the population).
(flowering age, 16-200+ years) generation time perhaps 40+ years
Number of mature individuals [over 12 cm dbh].
14
Total population trend.
Declining
% decline over the last 10 years or 3 generations.
72% decline over about 40 years (1 generation)
Are there extreme fluctuations in number of mature individuals?
No
Is the total population severely fragmented?
Yes, from main distribution in US
Specify trend in number of populations.
Currently one; possibly two smaller populations lost
Are there extreme fluctuations in number of populations?
No
Populations with number of mature individuals in each:
1) 15 Mile Creek: 14 mature trees; plus lost or unconfirmed in nearby sub-sites.


Threats (actual or imminent threats to populations or habitats)

The open site is prone to periodic severe storms off Lake Ontario.


Rescue effect (immigration from an outside source)

Status of outside population(s)?
USA: 3 populations within 70 km in western New York; an occasional forest species in the centre of its distribution.
Is immigration known or possible?
Unlikely
Would immigrants be adapted to survive in Canada?
Yes
Is there sufficient habitat for immigrants in Canada?
Limited additional habitat in Niagara
Is rescue from outside populations likely?
Possible but appears unlikely


Current status

Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Endangered (2006)


Recommended Status and Reasons for Designation

Status: Endangered
Alpha-numeric code: A2ac, B1ab (ii, iii, v) +2ab (ii, iii, v), C1 + 2a (i, ii), D1


Reasons for Designation: A widespread deciduous tree of eastern North America that is known from a single small population in Ontario. This population has declined considerably over the past four decades with fewer than 15 trees remaining in the wild. Its habitat is surrounded by residential development and the population is at continued risk from storms, erosion and habitat loss and degradation.


Applicability of criteria

Criterion A (Declining Total Population): Meets Endangered A2ac based on a loss of about 72% of trees in a single generation as noted by direct observation and is also associated with a decline in area of occupancy and quality of habitat.

Criterion B (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab (ii, iii, v) +2ab (ii, iii, v) due to the very small extent of occurrence and area of occupancy, presence of a single population and continuing decline in area of occupancy, quality of habitat and number of mature trees.

Criterion C (Small Total Population Size and Decline): Meets Endangered C1 + 2a (i, ii) based on the very small population size, likely continued decline of at least 20% in 2 generations and the single population has fewer than 250 mature trees.

Criterion D (Very Small Population or Restricted Distribution): Endangered D1 with only 14 trees and two saplings remaining.

Criterion E (Quantitative Analysis): Not available.

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