Climate change is warming Canada’s vast expanse of boreal forest, increasing the risk of fires and disease

CBC Alberta and Saskatchewan have collaborated on a new pilot series on weather and climate change in the prairies. Meteorologist Christy Climenhaga will bring her expert voice into the conversation to help explain weather and climate change and how it affects everyday life.


It is the largest least disturbed forest in the world. An expanse of trees that stretches all over the world, representing a third of the wooded area of ​​the Earth.

We are talking about the boreal forest. The coldest forest on the planet: a huge carbon deposit accumulated over thousands of years and a thriving ecosystem for plants and animals.

In Canada, over 300 million hectares of boreal forest stretch from the Yukon to the northern half of the provinces, east to Newfoundland. The boreal forest is home to half of the nation’s bird species and 3.7 million people.

As our climate changes, this great expanse of cold forest is warming. Average temperatures in the prairies are 1.9 ° C warmer since the mid-20th century, according to Environment and Climate Change Canada.

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Winters are becoming shorter and milder overall. Summers are getting warmer with little humidity to compensate for the heat. While some of these changes may seem small, they have a major impact on our local ecosystems, including the boreal forest.

So what will happen to this Canadian wilderness lighthouse as our climate continues to change? Will he survive?

Scientists say we are already seeing a change.

Climate change could push Canada’s boreal forest to crawl north. Here because

As summer weather increases, pests, forest fire risk, and changing rainfall could cause parts of our southernmost boreal forests to die, as the northern reaches expand in Arctic warming. Meteorologist Christy Climenhaga explains.

The Northern Lights are constantly changing

The change is nothing new for the boreal forest. It is constantly under pressure from natural disturbances – things like fire and insects – which can help the forest renew itself and become more resilient.

But what happens when these disorders occur more often, when they start to become the new normal?

This is the lens we are looking at as we continue to see our climate change at a rapid pace.

“If we think of drought, fire, insects and disease, this vast stretch is continually grappling with all of these threats. But under climate change at least some of these threats will become more serious,” says Janice Cooke, a science professor. biological at the University of Alberta.

Water stress and trees

As mercury climbs, evaporation occurs more easily and plants lose water at a high rate due to transpiration. When it is not replaced, we begin to run into a moisture deficit. And the longer those deficits last, the more stress they put on our plants.

“When trees face a water shortage, it’s pretty bad. They close the pores of the leaves and try to resist,” says Cooke.

By trying to conserve water, they get no sugar or resources they need to grow.

Cooke says that as growth is stunted, trees also lose some of their ability to remove carbon dioxide from the atmosphere, which begins to turn into a vicious cycle.

“We know those high temperatures create more drought. It’s a dangerous feedback loop.”

Water stress could affect growth along the southern edge of the boreal forest with climate change. (David Bajer / CBC)

The boreal and the prairies

Although you can imagine a skyline of boundless grasslands, the boreal forest covers more than half of our prairie provinces.

In Alberta and Saskatchewan, the northern half of both provinces is rooted in the boreal and in Manitoba it extends even further south, covering three-quarters of the province.

But the health of that forest is already changing in the Prairies.

Ted Hogg, researcher emeritus in the Canadian Forest Service’s climate change program, studies the deterioration of forest health.

“The big impacts we’re seeing are in northern Alberta, where we’ve had frequent severe droughts since 2002,” he says.

Hogg says the 2002 drought meant severe tree loss in the poplar park and southern borealis between Edmonton and Saskatoon. But recent droughts are extending that stress north.

“What we have seen more recently is that some other parts in places near Peace River, in northwestern Alberta and even in the Northwest Territories, have seen similar things happen … so poplar mortality has gone beyond that. we expected “.

According to Diana Stralberg, a researcher at the Northern Forestry Center with Natural Resources Canada, these stressors could lead to a forest shift towards a more prairie system.

“When there is a fire followed by drought, in which the seeds or seedlings do not survive and then are hit again by a fire, there is a risk that it can lead to a failure to regenerate the forest.”

Stralberg says that as we witness death in Alberta parks and the southern boreal regions, we may see the forest move north.

Smoke and flames from wildfires erupt behind a car on the highway near Fort McMurray, Alberta, Canada, May 7, 2016. According to Natural Resources Canada, climate change could potentially double the amount of northern boreal forest burned by 2100 compared to the last decades. (Mark Blinch / Reuters)

A march north

That ecosystem shift is no small feat, but it is something more scientists are seeing.

Logan Berner, assistant research professor at Northern Arizona University, studied the state of the global boreal region.

“There is emerging evidence that as the climate continues to warm, the boreal may shift north,” he says.

This shift would mean an expansion of boreal trees and shrubs into the Arctic and Alpine tundra and potentially a shrinking of the forest along the southern fringes, according to Berner.

In his research, Berner studies the browning and greening of trees, basically, where growth is increasing and where it is decreasing.

Berner surveyed a number of sites within the boreal forest between 1985 and 2019 to see how growth trends have changed. He says he saw an increase in greening at the northern end of the forest.

Berner’s study showed greater forest growth in the Arctic and more death in the prairie boreal forest. (Logan Berner, Scott Goetz / University of Northern Arizona)

“We think this is mainly due to the higher temperatures, which allow trees and shrubs to grow larger, expand their footprint and extend across the forest.”

Berner says that, in contrast to northern greening, there have been significant drops in vegetation gradients in parts of the southern boreal forest in North America and Eurasia.

“These are sort of early indications that a … change may occur.”

But even as trees begin to populate further north, Stralberg says, it may not make up for lost habitat in the south.

“You can lose the forest much faster than it can grow and provide habitat for wildlife. So if you lose an older forest here in the south, you don’t really have the opportunity to recover it anytime soon.”

Stralberg says this means that many species that depend on older mature forests, especially coniferous forests, could struggle.

“Since we have more open woodlands and more prairie conditions, you may see different species coming in. But the fact is, these things are happening so quickly that it’s really easy to have losses, especially when combined with all other human activities.”

Parasite stress

Insects form another piece of the northern climate puzzle as we continue to see warming.

As trees struggle with water shortages, this could mean openings for insects, says Jennifer Klutsch, a researcher at Natural Resources Canada and a forest entomologist.

“Drought stress can cause those trees to not be very well defended not only by native insects and pathogens, but also by range expansions such as the mountain pine beetle,” he says. “This can lead to greater outbreaks, frequency and severity.”

The green forests in and around Jasper National Park are increasingly marked by red and rust-colored trees, a sign that the mountain pine beetle has ravaged the areas. (Alex Zabjek / CBC)

It’s also about timing, says Klutsch. Insects, with their shorter life cycles, can respond more quickly to changes in temperature and humidity than trees.

“They can create populations and the trees are not really able to adapt to this new disturbance regime that is coming.”

And with warmer winters, insect populations could grow.

“If we don’t get the cold winters we expect in the boreal, that can lead to the maintenance of bark beetle populations due to the lack of winter mortality events.”

It’s too late?

Well, here’s the glimmer of hope.

While we are clearly seeing changes in our boreal region, changes can still be made.

“I think to some extent there is some inevitability on this warming trajectory that we have to respond to and adapt to,” says Stralberg. “I think we can reduce the damage to some extent.”

He says there is potential in looking at the landscape, finding the areas that are most resilient and trying to protect or conserve them.

“The areas that have larger bog complexes and more interfaces between mountain forests and bogs, I think there is more potential to really keep that water in the landscape,” he says.

According to Stralberg, small-scale changes in topography in specific locations where it is possible to have some shade and protection from direct sun and the ability to retain water also have potential.

Cooke agrees that there is still time for action to protect this vital ecosystem.

“Is it ever too late to do something better? I would say no. We can always try to do better and hope it will have an effect, but we can never go back in time.”


Our planet is changing. So is our journalism. This story is part of a CBC News initiative called “Our Changing Planet” to show and explain the effects of climate change. Keep up to date with the latest news on ours Climate and Environment page.

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