COSEWIC assessment and status report on the American Chestnut in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures, Tables and Appendices
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Technical Summary
- Acknowledgements, Authorities Contacted, and Information Sources
- Biographical Summary of Report Writer and Collections Examined
Range of Occurrence in Canada: southern Ontario
Extent and Area Information
Threats (actual or imminent threats to populations or habitats)
- chestnut blight fungus
- hybridization with Asian species of Castanea
- general habitat loss and fragmentation in the Carolinian Zone
Rescue Effect (immigration from an outside source)
USA: Natural populations in jeopardy
Assessed by COSEWIC in 1987 as Threatened
Status and Reasons for Designation
Reasons for Designation: Once a dominant tree in well drained forests of the Eastern Deciduous Forest, this species was devastated by chestnut blight in the first part of the 20th century. The species is still present throughout most of its former range, but as a few scattered individuals that have sprouted from root crowns. Most of these succumb to the blight before reaching a substantial size and fewer than 150 are large enough to produce seed. The species requires cross-pollination and seed set is reduced because mature individuals are widely scattered. Threats to the species include the continuous presence of the blight, aging and attrition of the root crowns, land clearing in some remaining sites, and hybridization with other species.
Applicability of Criteria
Criterion A (Declining Total Population):
Endangered under A4ace because there has been a well-documented decline of well over 50% in the number of mature trees within the last 70 years since chestnut blight spread across southern Ontario in the 1930s and 40s. Chestnut trees may reach fruiting condition in about 20 years, but usually succumb to blight as they reach maturity. Un-blighted trees lived for several hundred years. Seventy years thus represents fewer than 3 generations. Although American Chestnut occupies most of its former range, the AO has been reduced because the species now occurs as scattered individuals and some populations have been extirpated. Future losses will occur due to the deaths of root crowns.
Criterion B (Small Distribution, and Decline or Fluctuation):
Endangered due to limited distribution, fragmentation and decline under B2 (a)+(b, ii-v) with EO about 11 000 km2 but an AO of about 12 km2. Severely fragmented because only about 150 mature individuals are known and since the species is self-incompatible pollination is severely limited. Continuing decline anticipated in the AO and the number of locations as individual populations are extirpated and land clearing continues. The quality of forest habitat is declining in the Carolinian Zone from a number of causes (forest fragmentation, pollution, global warming, invasive species, pest and diseases). The number of mature individuals is projected to decline as individual rootstocks age and die and are not replaced from seed.
Criterion C (Small Total Population Size and Decline):
Endangered C2ai due to the small number of fruiting individuals (about 150) and very few mature individuals (<10) in any known population.
Criterion D (Very Small Population or Restricted Distribution):
Endangered under D1 due to the small number of mature individuals.
Criterion E (Quantitative Analysis):
- Date Modified: