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COSEWIC assessment and status report on the Butternut in Canada

Technical Summary

Juglans cinerea

noyer cendré

Range of Occurrence in Canada: Ontario, Quebec, New Brunswick

Extent and Area Information

Extent of occurrence (EO)(km2)
(Approximation of the area occupied by
the total range within the three provinces)
121 000 km2

Specify trend in EO

Likely stable

Are there extreme fluctuations in EO?


Area of occupancy (AO) (km2)

Unknown; distribution is scattered, and species is primarily found as lesser associates in hardwood stands with some extensive pure stands on floodplains

Specify trend in AO


Are there extreme fluctuations in AO?


Number of known or inferred current locations

Unknown; over 500 locations (stands) reported by landowners in Ontario; 378 plots reported in Quebec, with 39 plots in which butternut makes up ≥ 25% basal area; 50 locations reported in N.B. with about 370 stands

Specify trend in #

Unknown - trend data not available

Are there extreme fluctuations in number of locations?

No (to date, trees within stands are affected; it is anticipated that eventually stands will be lost)

Specify trend in area, extent or quality of habitat

Declining in southwest Ontario, stable in rest of range

Population Information

Generation time (average age of parents in the population)
30-60 years

Number of mature individuals


Total population trend:

Anticipated decline

% decline over the last/next 10 years or 3 generations.

No reliable data exist for calculating infection and mortality rates in Canada. Given the current geographic extent of the disease and based on available data for part of the range in Canada, Canadian populations may experience high rates similar to those in the USA (perhaps >70% decline).

Are there extreme fluctuations in number of mature individuals?


Is the total population severely fragmented?


Specify trend in number of populations

Anticipated decline

Are there extreme fluctuations in number of populations?


List populations with number of mature individuals in each: No complete data set is available

Threats (actual or imminent threats to populations or habitats)

- butternut canker is the most imminent threat; harvesting and habitat conversion to alternate land uses are concerns for parts of the range. 

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
up to 77% mortality in some states; continuing to decline

Is immigration known or possible?
Yes, possible, but major water barriers with few land bridges occur; potential recruitment populations are even more severely affected by canker than those in Canada

Would immigrants be adapted to survive in Canada?

Yes, from selected climatic regions, however, all populations appear to be susceptible to canker, with some individuals showing putative resistance

Is there sufficient habitat for immigrants in Canada?


Is rescue from outside populations likely?


Quantitative Analysis

Not Available

Current Status

COSEWIC: Endangered

Status and Reasons for Designation

Status: Endangered
Alpha-numeric code: A3e + 4e

Reasons for Designation: A widespread tree found as single trees or small groups in deciduous and mixed forests of southern Ontario, Quebec, and New Brunswick. Butternut canker, which has caused high rates of infection and mortality in the United States, has been detected in all three provinces. High rates of infection and some mortality have been observed in parts of Ontario and are predicted for the rest of the Canadian population.

Applicability of Criteria

Criterion A (Declining Total Population):
Endangered under A3 and A4 (i.e., introduced pathogens). It is likely to be met in Canada based on the severity of infection and mortality rates seen in similar forests in the United States and on similar high rates in Canada, based at least on Ontario data and evidence of widespread occurrence of infection in Eastern Canada.

Criterion B (Small Distribution, and Decline or Fluctuation):
Not available. No overall decline figures and range too large and not severely fragmented

Criterion C (Small Total Population Size and Decline):
Not available. Total population too large.

Criterion D (Very Small Population or Restricted Distribution):
Not available. Population and area of occupancy too large.

Criterion E (Quantitative Analysis):
Not available.