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A couple are dwarfed by old growth tress as they walk in Avatar Grove near Port Renfrew, B.C. on Oct. 5, 2021.JONATHAN HAYWARD/The Canadian Press

A new report offers the clearest picture to date of how forests in Canada’s national parks help fight climate change by storing large amounts of carbon, but also warns that this storage capacity is at risk from natural disturbances, especially wildfires.

The report, released last month by Parks Canada, is the first in a planned series of “carbon atlases” by researchers at the national parks service. The publications will look at how Canada’s protected areas capture, store and emit carbon dioxide, the primary greenhouse gas that results from human activities.

This initial research shows that forests in Canadian parks – from the rainforests of Haida Gwaii to the boreal forests of Wood Buffalo National Park – suck up heroic amounts of carbon and store it away in trees, soil and deadwood, year after year.

But it also shows that wildfires have, in some recent years, turned national park forests from a net sink of greenhouse-gas emissions to a net source, highlighting the threat such disturbances can pose to forests’ ability to help the country meet its goal of reaching net-zero emissions.

Parks Canada chief scientist Gilles Seutin said he sees the report as both a milestone – he believes it is the first time a country has published a detailed carbon analysis of its protected areas – and a potential management tool that could guide activities such as building new campgrounds or planting trees.

“Knowing the places where there is the highest potential for an ecosystem to capture and sequester more carbon, I hope in the future will become part of the decision on where to invest,” Mr. Seutin said.

The report also has implications for forests outside park boundaries. Globally, forests are the largest terrestrial carbon sink. They have removed more than one-quarter of emissions from fossil fuels over the past two decades, the report says. Canada has about nine per cent of the world’s forests, making all those trees a key part of the federal government’s biodiversity and climate pledges.

Forests act as carbon sinks when they absorb more carbon from the atmosphere than they release. That carbon is ingested by plants and transformed into wood and other materials. When plants die, decay or burn, that carbon is released back into the environment. If enough carbon is released this way, a forest can become a net carbon source, rather than a carbon sink.

The Parks Canada report says 5.6 million hectares of forested ecosystems in 31 national parks stored, on average, 1,452 megatonnes of carbon per year over the study period, from 1990 to 2020. That is equivalent, roughly, to 12 billion barrels of oil, according to a greenhouse-gas equivalencies calculator from Natural Resources Canada.

Researchers found the highest carbon densities in the Pacific Maritime Ecozone, a region that has older, wetter forests less prone to fire. It is home to three national parks: Gulf Islands National Park Reserve, in the Strait of Georgia; Gwaii Haanas, on Haida Gwaii; and Pacific Rim National Park Reserve, on the west coast of Vancouver Island.

Overall, forested ecosystems in the 31 national parks included in the study amounted to a small carbon sink over the study period.

But over that same period, the forests were a net source of greenhouse-gas emissions when those emissions were measured as CO2 equivalent, which takes into account other heat-trapping gases, including methane and nitrous oxide.

“Emissions from just two parks, Wood Buffalo and Waterton Lakes, outweighed the combined forest carbon sequestration in the other 29 parks, resulting in park forests being a net greenhouse gas source at the national level over the 31-year study period,” the report says. Both of those parks, located at opposite ends of Alberta, experienced large wildfires during the study period.

The fires “not only highlight how large disturbances can convert individual parks into net sources of GHGs, but also how disturbances in one large park or region can significantly impact the GHG balance of all national parks combined,” the report adds, using an abbreviation for greenhouse gases.

That pattern is part of a larger shift.

“What’s happening in the parks is a snapshot of what’s happening in Canada’s forests more generally,” said Ronnie Drever, senior conservation scientist with Nature United, a conservation group. “We’re seeing a diminishing carbon sink throughout the forests as a whole, largely as a consequence of increasing emissions from wildland fires and other disturbances that, together with logging, are diminishing our carbon sink.”

Fluctuations between carbon source or sink don’t mean forests aren’t still able to store carbon over time, said Karen Price, a British Columbia ecologist who was part of a provincially appointed panel on old-growth forests.

She drew a financial analogy. “Old-growth forests are our carbon banks, they are our capital,” she said. “The source and sink is like the interest.”

The study confirms previous research into the carbon-storing muscle of the old-growth forests of the Pacific Maritime Ecozone, especially when compared to newly planted trees, which take decades to grow to the point where they can store significant amounts of carbon, Dr. Price said.

“We need more parks in that zone. We need more parks in the coastal temperate rain forest. We need more parks in the inland temperate rain forest. We need to do that,” she said.

More conservation areas could be coming. A recently announced agreement between Ottawa, B.C. and the First Nations Leadership Council calls for protecting up to 13,000 square kilometres of old-growth forest in the province.

The Parks Canada study was completed before this year’s wildfire season, which as of early October had clocked in at 6,640 fires that had burned 18.4 million hectares across the country, according to the Canadian Interagency Forest Fire Centre. (The 25-year average is about 2.5 million hectares a year.) Preliminary estimates from Parks Canada suggest that during this time there were about 109 wildfires in 20 protected areas that burned an estimated 1 million hectares.

Changing climatic conditions across Canada are projected to increase the severity and frequency of wildfires and other disturbances, the Parks Canada report says. This would pose a challenge to the idea of using forests as natural climate solutions.

Researchers are looking at ways of mitigating wildfires, including prescribed burns – deliberately-set fires meant to reduce built-up fuel on the forest floor or achieve other ecological objectives, such as improving wildlife habitat.

Parks Canada routinely uses the practice. During the study period, prescribed fires were set in more than half of the 31 national parks studied, the Parks Canada report says. But those fires produced only 2 per cent as much emissions as wildfires did during that time.

The Parks Canada report holds lessons for other parts of the country, B.C. wildfire ecologist Bob Gray said.

“We can piggyback on the need to reduce our greenhouse-gas emissions with a whole bunch of other good things that come in reducing high-severity fires,” Mr. Gray said.

Those benefits could include a reduction in emissions that contribute to global warming, healthier air quality, less terrain burned and cost savings on fire suppression, insurance payouts and community evacuations.

At Parks Canada, carbon studies continue. With a forests atlas complete, future reports will analyze other ecosystems, including peatlands and grasslands. Inside Parks Canada, the report has been encouraging for staff and researchers who are sometimes weighed down by anxiety over climate change, Mr. Seutin said.

“It’s part of our stewardship of something that is of great value to Canadians,” he added.

“We are managing that huge amount of valuable resources, that stored carbon, for your kids, for your friends and for Canadian society in general.”

Editor’s note: A previous version of this story incorrectly said the forests of the 31 national parks in the report had stored the carbon equivalent of 12,000 barrels of oil annually between 1990 and 2020. This has been corrected.

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