Forests Are No Longer Our Climate Friends

David Wallace-Wells
Illustration by Sam Whitney/The New York Times; photographs by Chris Hellier and georgeclerk/Getty Images

Sept. 6, 2023

Canadian wildfires have this year burned a land area larger than 104 of the world’s 195 countries. The carbon dioxide released by them so far is estimated to be nearly 1.5 billion tons — more than twice as much as Canada releases through transportation, electricity generation, heavy industry, construction and agriculture combined. In fact, it is more than the total emissions of more than 100 of the world’s countries — also combined.

But what is perhaps most striking about this year’s fires is that despite their scale, they are merely a continuation of a dangerous trend: Every year since 2001, Canada’s forests have emitted more carbon than they’ve absorbed. That is the central finding of a distressing analysis published last month by Barry Saxifrage in Canada’s National Observer, ominously headlined “Our forests have reached a tipping point.”

In fact, Saxifrage suggests, the tipping point was passed two decades ago, when the country’s vast boreal forests, long a reliable “sink” for carbon, became instead a carbon “source.” In the 2000s, the effect was relatively small. But so far in the 2020s, Canada’s forests have raised the country’s total emissions by 50 percent.

“There is this feel-good myth in Canada that our massive forest is offsetting some of our massive fossil fuel emissions,” Saxifrage writes. “That might have been true decades ago under our old, stable climate. But we’ve so weakened our forest — through decades of business-as-usual industrial logging and fossil-fuelled climate shifts — that it has switched to hemorrhaging CO₂ instead of absorbing it.”

And, in theory at least, there is a lot more to hemorrhage: Saxifrage calculates that the 3.7 billion tons of carbon dioxide released by Canada’s forests since 2001 are only a small fraction of the 100 billion tons stored in its trees and soil. The trends there are not encouraging. “As extreme as this year’s wildfire emissions have been,” he says, “they are just the latest escalation in a multi-decade flood of CO₂ pouring out of Canada’s ‘managed’ forests and forestry.”

This is not a simple story of wildfire and climate change but also of logging and forest management. Roughly speaking, when trees logged and trees replanted and regrown are in balance, a forest’s ability to absorb carbon is stable. But beginning in the early 2000s, twice as much carbon-absorbing ability was destroyed through logging as was regenerated by replanting. In the decades since, the forest has largely stopped regenerating at all. In the 1990s Canadian forests were sequestering 165 million tons of carbon each year, 20 million more than the carbon-storage loss by logging. In the 2010s those same forests released 35 million more tons of carbon each year than they stored, not including the additional carbon released by logging. In the 2020s, that number has grown to 180 million tons released annually.


It all seems very Canadian. This is a country that promotes itself as a soft-spoken environmentalist leader, endowed with an endless forest landscape, but which nevertheless expands its pipelinesmocks the idea of leaving fossil fuels in the ground and routinely arrests climate activists. Canada is one of the few countries with more per capita emissions than the United States; in fact, its overall carbon production has actually grown since 1990, with the country producing more than 20 percent more carbon dioxide in 2019 than it did three decades earlier. This year, in the hellish midst of its worst fire season in modern history, Alberta actually hit pause on new renewable energy projects — a pause that may derail 118 projects worth $33 billion.

But the story is much larger than Canada. Over the past decade or two, the world has really invested in the promise of forests as a climate solution, not just in the vaguely conceived “billion trees” or “8 billion trees” or “trillion trees” proposals endorsed by supporters as various as Marc Benioff and Donald Trump and the World Wildlife Fund, but in elaborate offset projects and carbon-credit markets designed to mitigate the effects of industrial emissions by planting enough trees to absorb all that carbon through photosynthesis.

These proposals always stretched the veneer of plausibility. Planting a trillion trees would mean essentially standing up a new Amazon, and offsetting a meaningful share of the world’s fossil fuel emissions would require, it’s been estimated, turning over a third of the planet’s arable land to tree plantations. Offsetting all of them could require more than all the farmland on Earth. And because they eventually die, trees don’t store carbon permanently, even when they don’t combust and even when plantations are impeccably managed, which they rarely are.

But in recent months carbon offsetting has begun to look like an outright sham, with reports illustrating the emptiness of a vast majority of programs, particularly those that pay skimpily for poorly monitored projects in the developing world.

In one particularly scathing review in Science, researchers estimated that only 6 percent of 89 million carbon offsets would be associated with real carbon reductions. My colleague Peter Coy recently noted that the British bank Barclays suggested that the cost of offsets had fallen by more than three-quarters in just a year, a reflection of how little faith those buying them have in their reliability; voluntary carbon markets are shrinking for the first time in seven years out of growing skepticism. And last month in The Guardian, Patrick Greenfield speculated that carbon-credit speculators stood to lose many billions as the world came to realize that nearly all of the offsets being sold were “worthless.” A 2020 study showed that much-celebrated offsets sold for the Brazilian Amazon had barely slowed deforestation there. And a white paper published this summer by Joe Romm argued that the whole project of mitigating emissions through carbon offsets using forest replantation was “unscalable, unjust and unfixable.”

I wouldn’t be quite so fatalistic. Planting trees is still good, all else being equal, and can offer some climate benefits, if more limited ones than optimistic assessments suggest. And it is perhaps too cynical to judge offsets by the failures of the past. (If we judge all climate solutions by that standard, nearly all fail.) Even in a world of continued warming, some of the analyses show, forests can be managed better, deforestation more effectively combated and carbon more reliably stored. Logging practices can be reformed and deforestation in places like the Amazon can be reversed. In fact, under President Luiz Inácio Lula da Silva of Brazil, they already are, with rates of Amazon clearing down 34 percent from January to June.

But the world’s most precious rainforest is still in quite a lot of trouble, as Daniel Grossman documented last month in Nature. A 2021 review of 590 plane flights documenting forest behavior found that carbon uptake was weakening across the region and that in the southeast Amazon, the forest had already become a net source of carbon dioxide — raising alarm that the ecosystem may already be approaching a much-feared tipping point. Other studies have suggested that the rainforest as a whole may already have flipped from a carbon sink to a carbon source.

“What we were predicting to happen perhaps in two or three decades is already taking place,” one of those alarm-raising researchers told Grossman. And while policymakers discussing the transformation of the Amazon often emphasize the role of deforestation, which theoretically can be reversed, other research has suggested a larger impact of other warming-related changes, including fire. “We are killing this ecosystem directly and indirectly,” the climate scientist Luciana Gatti, who led the 2021 review, told Grossman. “This is what scares me terribly and why it’s affecting me so much when I come here. I’m observing the forest dying.”

Worrying trends have also been observed in the Congo basin. In less consequential places, such as the Czech Republic, countries have come to rely on forest uptake to manage their own carbon footprints — only to see those forests turned into carbon sources by warming. Some forests elsewhere in the world may offer more encouraging trends. But according to UNESCO, forests in 10 World Heritage Sites have been net carbon emitters over the past two decades. And for those of us raised on generations of naturalist fables — from “The Lorax” to “The Overstory” — the recent fires in Canada may be a disorienting cultural tipping point. If we thought trees might save us, that is looking increasingly like a foolish bet. In many parts of the world, including some of the most densely forested, trees are not perfect allies for tree-huggers anymore, and forests no longer reliable climate partners. What was once the embodiment of environmental values now seems increasingly to be fighting for the other side. In some places, fighting harder each year.


[Top: Illustration by Sam Whitney/The New York Times; photographs by Chris Hellier and georgeclerk/Getty Images]