American chestnut (Castanea dentata) COSEWIC assessment and status report: chapter 12

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Existing Protection or Other Status

The global ranking by NatureServe is G4 (apparently secure). In the American states, it is presumed extirpated (SX) in two peripheral states (Florida and Illinois), critically imperiled (S1) in two states (Michigan and Kentucky) and District of Columbia, and imperiled (S2) or vulnerable (S3) in seven states (Delaware, Georgia, Tennessee, Indiana, Ohio, Maryland, and Maine) and Ontario (NatureServe, 2003). In Canada it has been designated as Threatened by COSEWIC in 1987, as well as listed as threatened by the province of Ontario. Ontario’s Planning Act provides for the protection of significant portions of habitat of threatened species, but occupied habitats are being lost due to development. The Canadian Chestnut Council was founded in 1988 to bring awareness to the plight of this species and its potential for recovery.

There is currently a recovery team formed for this species and a recovery plan has been drafted (Boland et al., 2000); some of the information in the recovery plan has been summarized in this report. The current version of the recovery plan is available at the Canadian Chestnut Council website. The recovery plan proposes to: document all chestnut populations in Canada, promote recovery in the most critical of these populations, develop short-term management practices that will contribute to the conservation of the remaining genetic diversity of the species adapted to southwestern Ontario and assess more long-term strategies for managing chestnut blight. The latter includes seeking the identification or development of resistance in individual trees and working with potential biological controls such as naturally occurring hypovirulence in the blight organism.

Recovery through identification of natural resistance, and hypovirulent strains of the blight fungus that can be transferred to trees infected with virulent strains, is promising in principle. While early trials have been less than encouraging, signs of hope for these approaches remain (Griffin, 2000). Preliminary trials in Ontario with hypovirulence have been discouraging, whereas it has been very effective in controlling the blight in European forests and some positive results have been recorded in controlled settings in the US. Ex situ plantings of native chestnut are encompassed in the view of the recovery strategy, but have not been inventoried or assessed yet. Members of the Canadian Chestnut Council are actively pollinating naturally occurring trees and harvesting nuts for replanting. There is a difference of opinion within the recovery team as to whether breeding resistance into native trees via Asian species is a legitimate recovery action. Meanwhile, a breeding program is underway by the Canadian Chestnut Council, in partnership with similar operations by the American Chestnut Foundation.