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

CBC Alberta and Saskatchewan have teamed up for a new pilot series on weather and climate change in the Prairies. Meteorologist Christy Climenhaga will bring her expert voice to the conversation to help explain weather phenomena and climate change and their impact on daily life.

It is the largest least disturbed forest in the world. A stretch of trees sweeping across the globe, making up one-third of Earth’s forest area.

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

In Canada, more than 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 country’s bird species and 3.7 million people.

As our climate changes, this large expanse of cold forest is getting warmer. According to Environment and Climate Change Canada, average temperatures in the Prairies have been 1.9 C warmer since the mid-20th century.

Winters are getting shorter and milder overall. Summers are getting hotter with not enough humidity to offset the heat. Although some of these changes may seem small, they have big impacts on our local ecosystems, including the boreal forest.

So what will become of this beacon of Canadian wilderness as our climate continues to change? Will he survive?

Scientists say we are already seeing change.

Climate change could send Canada’s boreal forest crawling north. here’s why

As summer weather warms, pests, wildfire risks and changing precipitation could wipe out parts of our southernmost boreal forests, while the northern reaches expand into the Arctic. which is warming up. Meteorologist Christy Climenhaga explains.

Boreal is constantly changing

Change is not new to the boreal forest. It is under constant 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 disruptions happen more often, when they start to become the new norm?

It is the lens through which we look as we continue to see our climate change at a rapid pace.

“If we think of drought, fires, insects and disease, this vast expanse faces all of these threats all the time. But with climate change, at least some of these threats are going to become more severe,” says Janice Cooke, a professor of biological sciences at the University of Alberta.

Water stress and trees

When the mercury rises, evaporation occurs more easily and plants lose water at a high rate through transpiration. When not replaced, we begin to enter moisture deficits. And the longer these deficits last, the more they stress our plants.

“When trees are faced with a lack of water, it’s pretty bad. They close the pores in their leaves and they try to hold on,” Cooke says.

By trying to conserve water, they don’t get the sugars or resources they need to grow.

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

“We know these 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 an endless prairie horizon, 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 region, and in Manitoba it extends even further south, covering three-quarters of the province.

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

Ted Hogg, researcher emeritus with 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 resulted in a significant loss of trees in the aspen parkland and southern boreal forest between Edmonton and Saskatoon. But recent droughts are extending this stress north.

“What we’ve seen more recently is that other parties in places around Peace River, in northwestern Alberta, and even in the Northwest Territories, have seen similar things. occur…so aspen mortality has gone further than expected.”

According to Diana Stralberg, a research scientist at Natural Resources Canada’s Northern Forestry Centre, these stressors could cause the forest to shift to a grassland system.

“When you have a fire followed by a drought, where the seeds or seedlings don’t survive and then they are hit by fire again, you can have a risk that can lead to a lack of forest regeneration. “

According to Stralberg, as we see mass mortality in the parks and boreal regions of southern Alberta, we could see the forest moving 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 recent decades. (Mark Blinch/Reuters)

A march to the north

This ecosystem shift is no small feat, but it’s something that more and more scientists are seeing.

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

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

This shift would mean an expansion of boreal trees and shrubs into arctic and alpine tundra, and potentially a contraction of forest along the southern margins, according to Berner.

In his research, Berner studies the browning and greening of trees – basically, where growth increases and where it decreases.

Berner looked at a number of sites in the boreal forest between 1985 and 2019 to see how growth patterns changed. He says they have seen increased greening at the northern edge of the forest.

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

“We believe this is mainly due to the higher temperatures, allowing trees and shrubs to grow in size, spread their footprint and spread along the forest.”

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

“Those are kind of early indications that a…change might be happening.”

But even if trees start to populate farther north, Stralberg says, that may not make up for lost habitat in the south.

“You can lose forest much faster than it can grow and provide habitat for wildlife. So if you lose older forest here in the south, you don’t really have a chance to make it up very quickly. .”

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

“As we have more open forest and more grassland conditions, you can see different species coming in. But the thing is, these things happen so quickly that it’s really easy to have losses, especially when you combine with all other human activities.

Pest stress

Insects are another piece of the boreal climate puzzle as we continue to see warming.

As trees struggle with lack of water, that could mean openings for insects, says Jennifer Klutsch, a research scientist at Natural Resources Canada and a forest entomologist.

“Drought stress can cause these trees to not be very well defended against not only native insects and pathogens, but also range expansion, such as the mountain pine beetle. “, she says. “It can lead to larger outbreaks, frequency and severity.”

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

It also depends on the timing, says Klutsch. Insects, with their shorter life cycles, can react more quickly to changes in temperature and humidity than trees.

“They can build 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 increase.

“If we don’t get the cold winters we expect in the boreal region, it may cause bark beetle populations to persist due to the lack of winter kill events.”

It’s too late?

Well, here’s the silver lining.

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

“I think to some degree it’s inevitable that we’re on this warming trajectory that we have to respond to and adapt to,” Stralberg says. “I think to some extent we can reduce the damage.”

She says it is possible to look at the landscape, find the most resilient areas and try to protect or conserve them.

“Areas that have larger peatland complexes and more interfaces between upland forests and peatlands, I think there you have more potential to really keep that water in the landscape,” she says.

Small-scale topographic changes in specific places where you can have some shade and protection from direct sun, and the ability to hold water, also have potential, Stralberg says.

Cooke agrees there is still time to act 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 has an effect, but we can never turn back the clock.”

Our planet is changing. Our journalism too. 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 our Climate and environment page.

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