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This is well above normal levels for this part of the year and adds to the surge in emissions from massive wildfires in the American West in 2020. In California alone last year, fires produced more than 100 million tons of carbon dioxide, which was already enough. to more than offset the annual emission reductions in the wider region.

“Steady but slow decline [greenhouse gases] pale in comparison to those caused by wildfires, ”says Oriana Chegwidden, climate scientist at CarbonPlan.

Copernicus reported earlier this month that massive wildfires burning on millions of acres of land in Siberia are also littering the skies in eastern Russia and emitting tens of millions of tons of emissions.

In many parts of the world, forest fires and emissions are expected to only increase as climate change accelerates in the coming decades, creating hot and often arid conditions that turn trees and plants into tinder.

According to a recent study, fire risk – defined as the likelihood that an area will experience a moderate to high severity fire in any given year – could quadruple in the United States by 2090, even under scenarios where emissions are significantly reduced. in the coming decades, according to a recent study. researchers from the University of Utah and CarbonPlan. With fugitive emissions, the risk of a fire in the United States could be 14 times higher by the end of the century.

The emissions from the fires are “already bad and will only get worse,” says Chegwidden, one of the study’s lead authors.

“Very sinister”

Over longer periods, emissions and climate impacts from increasing wildfires will depend on how quickly the forests grow and reduce their carbon footprint, or if there are any. This, in turn, depends on the dominant trees, the strength of the fires, and how much the local climatic conditions have changed since the forest took root.

While working on her doctorate in the early 2010s, Camilla Stevens-Rumann spent the summer and spring months traveling through alpine forests in the Frank Church region of Idaho – River of Permanent Desert, studying the aftermath of wildfires.

She noted where and when coniferous forests began to return and where they did not, and where opportunistic invasive species such as Cheatgrass took over the landscape.

In a 2018 study published in the journal Ecology Letters, she and her co-authors concluded that trees burned in the Rocky Mountains had much more trouble growing this century, as the region got hotter and drier than at the end of the last … Dry coniferous forests, already teetering on the brink of viable conditions, are far more likely to simply morph into grasses and shrubs, which typically absorb and store far less carbon.

It can be useful to some extent by creating fire dams that reduce damage from future fires, says Stevens-Rumann, assistant professor of forest and rangeland management at Colorado State University. It could also help make up for a bit of the U.S. history of aggressively fighting fires that has led to fuel accumulation in many forests, and also increases the likelihood of major fires when they do ignite.

But their findings are “very ominous,” given the massive fires we are already seeing and the predictions of ever hotter and drier conditions in the American West, she says.

Other studies have noted that these pressures could begin to fundamentally transform forests in the western United States in the coming decades, damaging or destroying biodiversity, water, wildlife habitats and carbon stores.

Fires, droughts, insect infestations and changing climatic conditions will turn much of California’s forests into shrubs, according to a modeling study published in AGU Advances last week. The loss of trees can be especially significant in the dense forests of Douglas fir and coastal redwoods along the Northern California coast and in the foothills of the Sierra Nevada range.

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Overall, the state will lose about 9% of the carbon stored in trees and plants above the ground by the end of this century, under the scenario where we stabilize emissions this century, and over 16% in the future world where they will continue to grow. …

The study notes that, among other things, this will clearly make it harder for governments to use their land to capture and store carbon as part of forestry compensation and other climate change measures. California aims to be carbon neutral by 2045.

Meanwhile, the medium and high emission scenarios create “a real likelihood that Yellowstone’s forests will become non-forest vegetation in the mid-21st century,” because more frequent and larger fires will make it more and more difficult for trees to grow. , concluded a 2011 study published in Proceedings of the National Academy of Sciences.

The global picture

The net impact of climate change on fires and wildfires on climate change on a global scale is much more complex.

Fires directly contribute to climate change by releasing emissions from trees and also rich in carbon stored in soils and peatlands. They can also produce black carbon, which can eventually settle on glaciers and ice sheets, where it absorbs heat. This accelerates the disappearance of ice and the rise in ocean levels.

But fires can also generate negative climate feedback. The smoke from wildfires in the West, which has reached the East Coast in recent days, although dangerous to human health, carries aerosols that reflect some level of heat back into space. Likewise, wildfires in northern forests in Canada, Alaska and Russia could open up space for snow that is much more reflective than the forests they replaced, offsetting the heating effect of emissions.

Different parts of the globe also push and pull in different ways.

Climate change is exacerbating wildfires in much of the world’s forested areas, says James Randerson, professor of earth systems science at the University of California, Irvine and co-author of the AGU paper.

But the total area burned by wildfires around the world is actually shrinking, primarily due to shrinking savannahs and grasslands in the tropics. Among other factors, sprawling farms and roads are fragmenting the landscape in developing parts of Africa, Asia and South America, acting as a rift for these fires. Meanwhile, the growing herds are consuming fuel.

Overall, global emissions from fires account for about one-fifth of that from fossil fuels, although they have not increased dramatically so far. But total emissions from forests are clearly increasing when fires, deforestation and deforestation are included. According to the January Nature Climate Change report, they have grown from less than 5 billion tonnes in 2001 to over 10 billion in 2019.

Less fuel to burn

As warming continues over the coming decades, climate change itself will affect different areas in different ways. While many regions will become hotter, drier and more susceptible to wildfires, Randerson said, some cooler parts of the globe will become more conducive to forest growth, such as high mountain areas and parts of the Arctic tundra.

Global warming may also reach a point where it actually starts to reduce certain risks. If Yellowstone, California’s Sierra Nevada and other areas lose much of their forests, research suggests, fires in those areas could start to slow down by the end of the century. This is because there will simply be less or less combustible fuel to burn.

“Worldwide fire levels in the future will ultimately depend on both the rate of climate change and human activity, which is the main source of fires,” says Doug Morton, director of the Biosphere Science Laboratory at NASA’s Goddard Space Flight Center.