Three tree species have been assessed as at risk in Canada due to disease and alien insects, including the limber pine found here.
At a recent meeting in Ottawa, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed limber pine, which is found in montane and lower sub-alpine regions in B.C. and Alberta, as endangered.
Scientists say this tree species is imminently and severely threatened throughout its range by introduced white pine blister rust, mountain pine beetle and climate change, with predictions of a 67 per cent decline over the next 100 years.
“While each threat taken singly poses a significant threat, they interact to further increase the severity of the impacts,” said Bruce Bennett, co-chair of COSEWIC’s vascular plant specialist subcommittee.
“With climate change, the frequency, intensity and duration of drought is projected to increase and fire to be more frequent and severe. Stressed trees are likely to be more susceptible to pathogens and insects.”
Limber pine is a slow-growing, long-lived species. The oldest limber pine tree in B.C. is said to be 1,150 to 1,450 years old in Crowsnest Pass, while the oldest tree on record in Alberta is 991 years old, at Siffleur Ridge. Trees between the ages of 200 and 450 years are not uncommon.
A scrubby, twisted tree with short limbs, limber pine usually grows to between five and 12 metres high; the lower branches on older trees become very long and drooping, but with upturned tips.
Bennett said surveys at a number of sites in B.C. and Alberta in 2009 document an average of 43 per cent and 35 per cent of infected or dead trees, respectively.
He said repeated survey information leads to an estimated decline in the Canadian population of about one per cent per year.
“At that rate, close to two-thirds of mature individuals are expected to be lost over the next 100 years, and local subpopulations could become extirpated,” he said.
COSEWIC assessed two other tree species. The group concluded Blue Ash found in the Carolinian forests of southern Ontario as threatened because of the Emerald Ash Borer, an introduced pest affecting all native ash trees.
The situation is more dire for the Red Mulberry, another Carolinian forest species, now reduced to fewer than 200 trees and considered endangered in Canada. Multiple environmental stressors make trees less resistant to twig diseases.
