Climate risks put future of Canada’s boreal forests in jeopardy, scientists say

Large-leaf deciduous boreal forest with occasional Tsuga canadensis, Spruce and Cedar along Clyde Lake, Ontario, Canada. Photo credit: Arthur Chapman on Flickr
5 July 2018

BONN, Germany (Landscape News) — With climate change intensifying the risk of drought, fire, and insect infestations, Canada’s vast boreal forests, which cover 270 million hectares and encompasses 28 percent of the world’s boreal zone, face a highly uncertain future by the end of the century.

That was the finding of a team of scientists at Natural Resources Canada, whose paper on the subject was recently published in Ecological Applications.

“Effects of natural disturbances on wood volume have always been and will continue to be highly heterogeneous across the country both spatially and temporally,” the paper states.

“Some regions are projected to be affected essentially by one disturbance during the projected period, whereas other regions will likely cumulate the impacts of many disturbances that could compete with harvesting for timber supply. The result of greater concern is that, for a very large part of Canada, 90- to 100 percent of the total wood volume of the historical forest conditions could be at risk of being killed by disturbance under the climate conditions expected during the 2071-2100 period.”

The scientists chose the U.N. Intergovernmental Panel on Climate Change’s 8.5, or “worst-case-scenario,” model to make their predictions.

It is based on the continued emission of greenhouse gases at the current rate, and projects an average global temperature increase of between 4 and 5 degrees Celsius by the year 2100.

In northern areas such as Canada, however, the increase will be higher, as much as 7 or 8 degrees Celsius, said Yan Boulanger, a research scientist in forest ecology at the department’s Laurentian Forestry Centre in Quebec City, and one of the paper’s authors.

Researchers used data from the National Forest Inventory maps “that depict several attributes of the forest at the 250-metre scale all across Canada,”said Boulanger. They looked at seven ecozones across the country, and at their baseline inventory for 2001.

They then estimated how the boreal forest would likely respond to the most critical disturbances it faces, drought, wildfires, and two types of insect pest, spruce budworm (Choristoneura) in the eastern part of Canada and mountain pine beetle (Dendroctonus ponderosae) in the West.

Researchers analyzed vulnerability to disturbances in three 30-year periods. In the short term, for example, drought will have a harmful impact on moisture-loving species such as trembling aspen (Populus tremuloides), a tree favored by wildlife such as deer, elk, and moose.

“The closer you come to 2100 the more severe the impacts on forest because of the increasing temperature and drought conditions,” said Boulanger.

“The drier, warmer weather will increase the incidence of forest fires, which is already a major threat to Canada’s forests. “All of the central part of Canada will experience fire activity that might be five, six, or seven times what we are experiencing right now,” he said.

What’s more, the higher temperatures will create ideal climactic conditions for the survival and spread of the Mountain Pine Beetle (Dendroctonus ponderosae). All species of pine are vulnerable to the beetle, and winter temperatures of less than -40 Celsius are required to kill the insect, which has wreaked havoc in forests due to hotter, dryer conditions in recent years.

“In the future,” said Boulanger, “we are projecting that those conditions that are triggering survival of Mountain Pine Beetle will occur much more often.”

While the predictions are dire, Boulanger said that efforts could and should start on climate adaptation and mitigation. “The first objective of this paper was to identify those areas that might be vulnerable to climate change,” he said.

“We are still at the stage of identifying the vulnerability of the forest to climate change, but once we have identified those vulnerabilities, it could be less difficult to implement, or to think about, strategies that could be employed by the forest industry, or by any other sector that will be affected by climate change impact on the forest.”

Coniferous species, for example, are much more prone to fire than broadleaf species. “So if there is more broadleaf species in the landscape, probably your landscape will be less vulnerable to fire activities,”” he explained. Forest managers might also look at planting more drought-resistant tree species as well.

“We are actually collaborating with the provincial agencies on this topic to help them find actions or strategies that might help them adapt to the changes that are projected,” he said.