The pandemic has reduced West Coast emissions. The forest fires have already reversed it.


This is well above normal levels for this part of the year and comes on top of increased emissions from wildfires across the American West in 2020. California fires alone have produced More than 100 million tons of CO2 last year, which was already enough to more than cancel out annual declines in emissions for the broader region.

Steady but slow cuts in [greenhouse gases] It’s pale compared to those caused by wildfires, says Oriana Cheguden, a climate scientist at CarbonPlan.

The massive wildfires that have burned across millions of acres in Siberia are also clogged sky Through eastern Russia and releasedفراج Tens of millions of tons of emissionsCopernicus reported earlier this month.

Fires and forest emissions in many regions of the world are only expected to increase as climate change accelerates in the coming decades, creating hot, often dry conditions that turn trees and plants into squid.

Fire risk — defined as the chance that an area will experience a moderate to severe fire in any given year — could quadruple across the United States by 2090, even under scenarios in which emissions drop dramatically in decades. coming, recent study by researchers at the University of Utah and CarbonPlan. With uncontrolled emissions, fire risks in the United States could be 14 times higher towards the end of the century.

Emissions from the fires are “really bad and they’re going to get worse,” says Chiguiden, one of the study’s lead authors.

“Very ominous”

Over longer periods, the emissions and climate impacts of increased wildfires will depend on how quickly forests grow again and withdraw carbon again – or whether they do so at all. This in turn depends on the dominant trees, the intensity of the fires, and how much local climatic conditions have changed since that forest took root.

While working on her PhD in early 2010, Camille Stephens Roman spent the summer and spring months trekking through the alpine forests of Frank Church – a River of No Return in Idaho, studying the effects of fires.

She noticed where and when coniferous forests began to return, where they did not, and where opportunistic invasive species such as cheaters have taken over the landscape.

in a Study 2018 In Ecology Letters, she and her colleagues conclude that trees burned across the Rocky Mountains had much greater problems growing again this century, as the area got hotter and drier, than at the end of last century. Dry coniferous forests that were already teetering on the edge of viable conditions were much more likely to simply convert to grasses and shrubs, which absorb and store less carbon overall.

This can be somewhat healthy, says Stevens Roman, associate professor of forest and range management at Colorado State University, creating fire breaks that reduce future fire damage. It could also help offset somewhat of the US history of putting out fires aggressively, allowing fuel to build up in many forests, and it also increases the odds of major fires when they do catch on.

But their findings are “ominously ominous” given the wildfires we’re already seeing and the outlook for increasingly dry and hot conditions across the American West, she says.

Other studies have indicated that these pressures could begin to fundamentally transform western US forests in the coming decades, damaging or destroying biodiversity and water sources, wildlife habitats, and carbon storage.

Fires, droughts, insect infestations and changing weather conditions will turn large parts of California’s forests into shrubs, according to the modeling study Posted in AGU Advances last week. Tree losses can be particularly severe in the dense forests of Douglas-fir and coastal redwood forests along the northern California coast and in the foothills of the Sierra Nevada mountain range.

Kings Canyon National Park after a forest fire
Kings Canyon National Park, in California’s Sierra Nevada mountain range, after a recent forest fire.

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Finally, the country will lose about 9% of the carbon stored in trees and plants above ground by the end of this century under a scenario in which we fix emissions this century, and over 16% in a future world where they continue to rise.

Among other effects, this would clearly complicate the country’s dependence on its land for carbon capture and storage forest compensation program and other climate efforts, the study notes. California is striving to become carbon neutral by 2045.

Meanwhile, medium to high emission scenarios create a “real potential for Yellowstone forests to be converted to non-forest vegetation during the mid-21st century,” because increased common and large fires will make it more difficult for trees to grow again and Study 2011 In the Proceedings of the National Academy of Sciences concluded.

global picture

The net impact of climate change on fires and fires on climate change is more complex globally.

Fires directly contribute to climate change by releasing emissions from trees as well as the rich carbon stored in soil and peatlands. They can also produce black carbon that may eventually settle on glaciers and ice sheets, where it absorbs heat. This is accelerating ice loss and rising ocean levels.

But fires can also trigger negative climate reactions. The smoke from the western wildfires that reached the east coast in recent days, while terrible to human health, Carrying aerosol that reflects a certain level of heat back into space. similarly, Northern forest fires In Canada, Alaska, and Russia it could open up an area of ​​snow much more reflective than the forests it replaced, offsetting the heating effect from the emissions released.

It also pushes and pulls different parts of the globe in different ways.

Climate change is exacerbating wildfires in most of the world’s forest regions, says James Randerson, professor of Earth system sciences at the University of California, Irvine, and one of the authors of the AGU paper.

But the total area burned by fires around the world is actually go down, thanks primarily to tapering across savannas and grasslands in the tropics. Among other factors, sprawling farms and roads are fragmenting landscapes in developing parts of Africa, Asia and South America, creating breaks for these fires. Meanwhile, the growing herds of cattle are devouring the fuel.

In general, global emissions from fires are about one-fifth of fossil fuel levels, although they are Do not rise sharply Until now. But it is clear that total emissions from forests are rising when they include fires, deforestation and logging. It has grown from less than 5 billion tons in 2001 to more than 10 billion in 2019, according to Climate Change Nature Paper in january.

Less fuel to burn

As warming continues in the coming decades, climate change itself will affect different regions in different ways. While many regions will become hotter, drier, and more susceptible to wildfires, some colder parts of the globe will become more suitable for forest growth, such as the high elevations of tall mountains and parts of the arctic tundra, Randerson says.

Global warming could also reach a point where it really starts reducing certain risks as well. If Yellowstone, California’s Sierra Nevada, and other areas lose large portions of their forests, studies have suggested, the fires may begin to decline toward the end of the century. This is simply because there will be less or less flammable fuel to burn.

It’s difficult to make reliable predictions about global forest and fire emissions in the coming decades because there are so many competing and unknown variables, including what actions humans will decide to take, says Doug Morton, chief of the Biosphere Science Laboratory at NASA’s Goddard Space. Flight Center.



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