As Formerly Frozen Tundra Deteriorates, Scientists Find Evidence For Rapid Treeline Advance

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EDMONTON • University of Alberta scholars are warning that Canada’s frozen North is increasingly going green, with forests of trees and shrubs advancing into territory that was once barren tundra at a what could be a dangerously high rate, fuelled in part by warmer temperatures.

Rapidly declining tundra will have dire effects on caribou, wild sheep and other species that live in such habitat — as well as for indigenous people who hunt the animals — the researchers argue in a new study that offers further evidence of the effects of climate change.

“Because conditions are so cold at the treeline, conventional wisdom has said that if trees are going to advance, they will do so very slowly and sort of creep forward,” said Ryan Danby of the U of A’s department of biological sciences. “What our findings show is that if conditions are right, they can surge ahead at a fair clip.” Over the five-year project, Dandy and fellow biologist David Hik analysed samples from about 850 trees and 900 willow shrubs taken from the Kluane Wildlife Sanctuary in southwest Yukon.

By looking at the tree rings, the scientists could precisely date each tree’s year of establishment and year of death — information that allowed them to reconstruct changes in the area’s climate and vegetation over the last 300 years. “We found that the treeline was actually very stagnant until about 1925 — no real advance and no real recession,” Danby said. However, over the next several decades, tree-ring evidence showed a rapid expansion in response to climate warming.

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