The pandemic has drastically cut emissions on the west coast. The wildfire has reversed it.

This is much higher than the normal level for this part of this year, and is based on a surge in emissions caused by a large-scale fire in the western United States in 2020.California fire alone caused More than 100 million tons Last year’s carbon dioxide emissions were enough to offset the annual decline in emissions in the wider region.

“Steady but slowly decreasing [greenhouse gases] Said Oriana Chegwidden, a climate scientist at CarbonPlan.

Millions of acres of massive wildfires in Siberia are also burning Block the sky Across the eastern part of Russia and release Tens of millions of tons of emissions, Copernicus reported earlier this month.

As climate change accelerates in the coming decades, it is expected that fire and forest emissions in many parts of the world will only increase, creating hot and often dry conditions and turning trees and plants into fire.

Fire risk—defined as the probability of a moderate to high level of fire in an area in any given year—may quadruple in the United States by 2090, even if emissions fall significantly in the next few decades, according to One item A recent study Researchers at the University of Utah and CarbonPlan. If emissions are not controlled, the fire risk in the United States may be 14 times higher by the end of this century.

All Gwidden, the lead author of the study, said that the emissions from the fire are “already bad and will only get worse”.

“Very ominous”

In the longer term, the effects of increasing wildfires on emissions and climate will depend on how quickly forests can regenerate and absorb carbon – or whether they actually do so. In turn, it depends on the main trees, the severity of the fire, and how much local climate conditions have changed since the forest took root.

During his PhD in the early 2010s, Camille Stevens-Rumann hiked through the alpine forests of Frank Church-River of No Return Wilderness in Idaho during the summer and spring months to study the aftermath of fires.

She pointed out when and where coniferous forests began to recover, where they did not recover, and where opportunistic invasive species like paramecium took over the landscape.

in a Study in 2018 In “Ecology Letters”, she and her co-authors concluded that compared with the end of the last century, the trees burned in the Rocky Mountains this century have encountered growth problems as the area has become hotter and drier. It’s more difficult. Dry coniferous forests that are already crumbling on the edge of living conditions are more likely to simply turn into grasses and shrubs, which generally absorb and store much less carbon.

Stevens Ruman, assistant professor of forest and ranch management at Colorado State University, said this is healthy to a certain extent and can create fire interruptions and reduce future fire damage. It can also help make up for the United States’ history of aggressive firefighting, which has allowed fuel to accumulate in many forests and increased the likelihood of major fires.

But she said that in light of the large-scale fires we have seen and the forecast of increasingly hot and dry weather in the western United States, their findings are “very ominous.”

Other studies have pointed out that these pressures may begin to fundamentally change the forests of the western United States in the coming decades, destroying or destroying biodiversity, water, wildlife habitat, and sources of carbon storage.

According to reports, fires, droughts, pests and changes in climatic conditions will turn most of California’s forests into bushes. Modeling research Published on AGU Advances last week. Tree loss can be particularly severe in the dense Douglas fir and coastal redwood forests on the coast of Northern California and the foothills of the Sierra Nevada Mountains.

A forest fire broke out recently in Kings Canyon National Park in the Sierra Nevada Mountains of California.

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All in all, with our stable emissions this century, the state will lose about 9% of the carbon stored in the trees and plants on the ground by the end of this century, and in the future world, carbon will continue to increase and will lose more than 16%.

Among other effects, this will obviously complicate the state’s reliance on its land to capture and store carbon through its land. Forestry compensation The study points to the plan and other climate efforts. California is working hard to achieve carbon neutrality by 2045.

At the same time, the medium-to-high emission scenario creates “the real possibility that Yellowstone forest will be transformed into non-forest vegetation in the middle of the 21st century”, because increasingly common and large fires will make it more and more difficult for trees to grow again. A study in 2011 Conclusions are drawn in the Proceedings of the National Academy of Sciences.

Global picture

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

Fires directly cause climate change by releasing emissions from trees and the abundance of carbon stored in soil and peatlands. They can also produce black carbon, which may eventually settle on glaciers and ice sheets, where they absorb heat. This accelerates the loss of ice and the rise of sea levels.

But fires can also cause negative climate feedback. Although the smoke from the western wildfires that have reached the east coast in recent days is harmful to human health, Carry aerosol Reflect a certain degree of heat back into space. Similarly, Boreal forest fire In Canada, Alaska, and Russia, space can be created for snow that is more reflective than the forests they replace, offsetting the thermal effects of releasing emissions.

Different regions of the world are also promoting and pulling in different ways.

James Landerson, professor of earth system science at the University of California, Irvine and co-author of the AGU paper, said climate change is making wildfires in most forested areas of the world worse.

But the total area of ​​the world destroyed by fire is Actually down, Mainly due to the reduction of savanna and grassland. Among other factors, sprawling farms and roads are destroying the landscapes of developing regions in Africa, Asia, and South America, becoming the breakthrough point for these fires. At the same time, more and more livestock are devouring fuel.

Overall, global fire emissions are about one-fifth of fossil fuel emissions, although they Did not rise sharply to date. However, if you include fires, deforestation and logging, the total emissions of forests have clearly been rising. According to a report, they have grown from less than 5 billion tons in 2001 to more than 10 billion tons in 2019. Natural Climate Change Paper In January.

Less fuel to burn

As warming continues in the coming decades, climate change itself will affect different regions in different ways. Landerson said that although many areas will become hotter, drier and more prone to wildfires, some colder areas around the world will become more suitable for forest growth, such as high mountains and parts of the Arctic tundra.

Global warming may also reach a level that actually begins to reduce certain risks. If most of the forests in Yellowstone National Park, California’s Sierra Nevada and other areas disappear as studies have shown, then by the end of this century, fires may begin to fall. That’s because less fuel is burned, or less flammable.

Doug Morton, director of NASA’s Goddard Space Biosphere Science Laboratory, said that it is difficult to make reliable predictions of global forest and fire emissions in the next few decades because there are too many competing variables and unknowns, especially Including the flight center that humans will decide to take.

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