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New research reveals what scientists have learned about the scale and distribution of a massive carbon reservoir lying just below the surface in wilderness areas across the country — and what’s at stake for the planet if it’s disturbed

Seen from above, much of Canada looks like a landscape built out of carbon.

In towering West Coast groves and across the boreal forest that spans much of the country, trees and other vegetation have trapped billions of tonnes of carbon – all of it ripped from the air, atom by atom, to sustain plant growth. This vast reserve is an asset in the battle against climate change, containing more carbon than Canadian cars and factories combined have released in more than a century.

But this living carbon capture and storage system is only the tip of the iceberg. Beneath the trees, the leaf litter and the networks of roots are deep layers of peat and carbon-rich soil, the decomposed remains of plants that have been accumulating since the end of the last ice age, some 10,000 years ago.

Mean carbon density

Forest carbon*4.4 kg/m2
Soil carbon**45.7 kg/m2
* Includes above ground biomass, below ground biomass (roots) and dead plant material.
** Soil to a depth of one metre.

In an effort to better understand the country’s natural carbon sinks, researchers are increasingly looking below the surface.

In the top metre of soil alone they have discovered an enormous storehouse of buried carbon that far exceeds what has been measured in all of Canada’s forests combined.

This is carbon that for millennia has been kept from circulating in our atmosphere. Now, scientists and conservation groups say it must remain intact to avoid magnifying the threat of global warming.

On Wednesday, at the United Nations climate conference in Glasgow, WWF Canada is set to release the most detailed map ever produced of the country’s carbon stocks, based on data gathered and analyzed in collaboration with researchers at McMaster University in Hamilton, Ont.

The map divides Canada’s land area into a mosaic of squares 250 metres across and shows the distribution of all the carbon stored in its forests and plant life – a total of 21.1 billion tonnes. To this it adds a new estimate of soil carbon, achieved through a combination of field data, remote sensing and machine learning.

That estimate comes in at a staggering 384 billion tonnes. And while there are large uncertainties around the figure – the precise amount of soil carbon ranges between eight and 28 times what is stored in plants – there is no doubt it represents the largest share of Canada’s carbon stocks by far. The areas rich in soil carbon are diverse and complicated, and some are acting as carbon sinks, taking up some of the carbon dioxide we are emitting by burning fossil fuels. But much of that soil carbon lies in places where disturbing it could wreak havoc with Canada’s net-zero emissions goals.

“It’s a globally important amount in terms of its broader implications for the climate … And it’s important in terms of our responsibility to steward and protect those places,” said James Snider, WWF Canada’s vice-president of science, knowledge and innovation.

Regional diversity

An obvious and important feature of the soil carbon is that it is not evenly distributed, neither in geographic extent nor in terms of its richness in the ground. This suggests the map can also serve as a guide for prioritizing regions for protection as Canada tries to fulfill an international commitment to conserve at least 30 per cent of its territory by 2030. And it is also crucial information for Indigenous peoples making the case for maintaining their traditional territories.

Carbon captured in nature by province

Soil carbon (0-1m)

Forest carbon

Manitoba

110

3.4

Ontario

82.6

4.8

NWT

48.7

2.7

N.L.

3.8

47

Quebec

4.3

45.7

B.C.

42

6.2

Yukon

35.1

3.6

Atlantic

34.6

3.1

Saskatchewan

32.8

4

Nunavut

31.1

2

Alberta

22.9

5.2

0

40

80

120

Mean density (kg/m2)

THE GLOBE AND MAIL, SOURCE: WWF CANADA

Carbon captured in nature by province

Soil carbon (0-1m)

Forest carbon

Manitoba

110

3.4

Ontario

82.6

4.8

NWT

48.7

2.7

N.L.

3.8

47

Quebec

4.3

45.7

B.C.

6.2

42

Yukon

35.1

3.6

Atlantic

34.6

3.1

Saskatchewan

32.8

4

Nunavut

31.1

2

Alberta

22.9

5.2

0

40

80

120

Mean density (kg/m2)

THE GLOBE AND MAIL, SOURCE: WWF CANADA

Carbon captured in nature by province

Soil carbon (0-1m)

Forest carbon

Manitoba

110

3.4

Ontario

82.6

4.8

Northwest Territories

48.7

2.7

Newfoundland and Labrador

3.8

47

Quebec

4.3

45.7

British Columbia

6.2

42

Yukon

35.1

3.6

Atlantic Provinces

34.6

3.1

Saskatchewan

32.8

4

Nunavut

31.1

2

Alberta

22.9

5.2

0

20

40

60

80

100

120

Mean density (kg/m2)

THE GLOBE AND MAIL, SOURCE: WWF CANADA

Overall, Manitoba and Ontario have the highest average densities by large margins. This is because the boundaries of both provinces overlap with some of Canada’s highest concentrations of peat. But the new analysis suggests there is a more extensive and varied storehouse than previously appreciated.

Exploring the underground

The map was created to help with a broader effort in conservation science to better quantify ecosystem services – the things nature does and provides that make life possible for people around the world. At a time when countries are debating carbon pricing schemes as a way to reduce emissions, the ability of a natural landscape to hold carbon indefinitely comes with measurable value.

By touring around Canada’s new carbon map, it’s possible to get a sense of where that value lies.

Combined biomass and soil carbon (kg/m2)
1 150+
Biomass carbon (kg/m2)
0.05 10+
Soil carbon (kg/m2)
0.7 150+
1
2
3

THE GLOBE AND MAIL, Source: WWF CANADA

Previous efforts to map carbon on a national scale have already shown that a large boggy expanse adjacent to Hudson Bay and James Bay is the most obvious area of high-density storage.

One surprise in the new analysis is that this region appears to stretch much farther to the south and west than in earlier maps and is contiguous with another large carbon-rich area around Lake Winnipeg.

These areas are vulnerable because they coincide with areas that are of interest for resource development.

On the West Coast, areas that are richest in soil carbon coincide strongly with mature forests that hug the B.C. coastline.

This region encompasses some of Canada's greatest biodiversity, including several species at risk. Here carbon storage provides additional incentive to maintain the natural landscape.

Sweeping northward, carbon-dense soil forms a diagonal band from the Mackenzie River Delta down to the northern reaches of the Prairies.

The region includes peatlands that are part of Canada’s Subarctic and also extend into the northwestern boreal forest. As climate change raises temperatures in this region at a faster rate than the global average, carbon stored here is at risk of escaping back into the atmosphere due to melting permafrost and more forest fires.

The map also shows that carbon-rich soils are present in smaller but significant pockets across the country, including Northern Quebec and the Labrador coast.

There is currently no way to directly sample a territory as large as Canada in order to build such a map, particularly because so much of the country’s land area is so difficult and expensive for researchers to access. This has made it a challenge for those who are trying to pin down exactly how much carbon is stored in Canada’s landscape.

To overcome this obstacle, Alemu Gonsamo, who leads McMaster University’s Remote Sensing Group, and Camile Sothe, a postdoctoral researcher, used a learning algorithm – a computer program they trained to estimate carbon content based on satellite data they linked to field measurements. They then tested the algorithm on a second set of data to ensure its performance before setting about building a national map. The entire project took two years to complete.

“The biggest finding is that the amount of carbon in the top one metre of soil is so huge compared to other estimates,” Dr. Gonsamo said, adding that it exceeds the amount stored in the Amazon rainforest.

The group is now working to narrow the uncertainties around its results. They have begun a follow-up study that would involve working with an Indigenous team to gather more field data in some of the highest-density carbon regions near Hudson Bay.

An aerial shot of the Hudson and James Bay Lowlands.WWF-Canada/Casa di Media Productions

A large share of Canada’s soil carbon reserve is in the form of peat, a type of soil that is rich in organic matter and has outsized importance because it stores 20 to 30 per cent of the world’s carbon in just 3 per cent of its surface area.

Lorna Harris, an ecosystem scientist at the University of Alberta, is the lead author on a separate analysis of Canadian peatlands, which account for a quarter of the global total. According to that study, also presented this week at the UN climate conference, at least 12,000 square kilometres of peatlands have already been disturbed by agricultural and other activities. Meanwhile, Canada’s stated goal of achieving net-zero emissions by 2050 depends on global carbon sinks, including peatlands, absorbing about half the carbon dioxide released by human activity.

The consequences of losing more of that carbon sink and potentially turning it into yet another source of atmospheric carbon is something Canada has not yet fully taken on board. The pathways for doing so are numerous, including the effects of mining, forestry, road building, drainage and seismic lines.

“We can say we’ve got the carbon under ground but we don’t yet have the knowledge to assess those impacts,” Dr. Harris said.

Critically, this includes the development of Northern Ontario’s Ring of Fire region, which Premier Doug Ford said Tuesday he would like to see mined for raw materials needed for the transition to electric vehicles.

An aerial shot of the Hudson and James Bay Lowlands.WWF-Canada/Casa di Media Productions

But the area sits squarely in the midst of some of the richest peatlands in Canada. If measures are not taken to protect its stored carbon, its exploitation will invariably increase the country’s carbon output.

“If you don’t have a long-term perspective on managing these areas, you can lose a ton of emissions that will undermine all of our other efforts,” said Justina Ray, the president of the Wildlife Conservation Society Canada, who co-authored the analysis.

She added that peatlands are not included in Canada’s national inventory of emissions and contributions to reducing climate change under the 2015 Paris Agreement.

Matthew Mitchell, a University of British Columbia researcher who specializes in ecosystem services and was not involved in either study, said the new results set the stage for more detailed investigations of Canada’s buried carbon, including how it is changing as the planet warms.

“If you don’t know what you have, you don’t know what you’ve lost,” he said. “And if we can understand better what the threats are to that carbon, then we can start to come up with strategies for how to keep it in the ground.”

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