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Polluters are using forests as ‘carbon offsets.’ Climate change has other plans.
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Polluters are using forests as ‘carbon offsets.’ Climate change has other plans.


On July 6, 2021 lightning set off a fire in the Fremont–Winema National Forest in southern Oregon. This was in an area populated with dead trees due to a mountain pine-beetle epidemic. The Bootleg fire, which was fueled by drought, erupted and consumed 1,000 acres per hour. The national forest was engulfed in flames, which raced through white pine, ponderosa and lodgepole pine. Green Diamond, a timber company.

Elizabeth Willmott was located hundreds of miles north in a Seattle suburb and was closely following events. As the carbon program director for technology giant Microsoft, she had a special interest in Green Diamond’s Klamath East forests: They were storing some of her company’s carbon.

Microsoft has committed one of the country’s most ambitious corporate carbon-cutting programsMicrosoft aims to achieve net-zero emissions by 2030. This is not only for its factories and buildings, but also for its supply chain. Microsoft announced that it would invest in projects that would reduce emissions. However, this will take several years. 1.43 million tonnes of carbon dioxideFrom the heavens. This included 265,000 tons CO2 that Microsoft had hired Green Diamond to remove. Increasing the tree’s growth—many of which had just gone up in smoke in the Bootleg fire, returning their carbon to the atmosphere.

As companies face increasing public pressure to limit their climate impact, the global market for forest carbon “credits,” already worth billions of dollars, is booming. As an alternative to cutting carbon from burning oil, gas and coal, polluting businesses can purchase these credits. Such “offsets” have been questioned on many grounds, including whether they actually reduce carbon in the atmosphere.

Scientists are now more focused on climate change. With Trees are dying all over the worldFrom Droughts, heat waves and pest invasions can all be caused by wildfires. amplified by global warming, experts say, it’s getting tough to count on any particular patch of forest being alive and reliably storing carbon for decades to come.

“Climate change already poses substantial risks to forest carbon, and those risks will go up dramatically in the 21st century,” says Bill AndereggThis issue was extensively studied by Dr. Judith A. Smith, University of Utah forest ecologist. “Forest offset protocols have not rigorously or thoroughly grappled with those risks.”

Microsoft was more thorough than others. Green Diamond was even more rigorous than most. A California state agency also vetted the forest-carbon credits it sold and verified that they could legitimately offset emissions.

But there is more. Carbon-science watchdog releases new analysis CarbonPlan suggests the California offset program, which is among the world’s largest, doesn’t account for how fast forests are changing. The program allows for the fact that wildfires can release stored carbon—but in less than 10 years, according to CarbonPlan, fires may already have released nearly as much carbon as the state budgeted for the next century.

And flames aren’t the only threat to offsets. The study also claims that the carbon losses from a single deadly tree disease—sudden oak death—may be as high as the state projected from all diseases and insect infestations combined.

“If we’re going to keep using forests to offset emissions, we need to start being way more realistic about the threats those forests face,” says Grayson Badgley, a former postdoctoral researcher in Anderegg’s lab and lead author of the CarbonPlan study.

Good intentions

Willmott is the best at understanding the stakes. Before joining Microsoft 2016, she’d spent years working in local government and as an activist trying to get organizations to reduce fossil fuels. Microsoft now has zero-carbon energy and is electrifying its vehicles with her support. It’s going beyond cutting or offsetting its current emissions: By 2050 the company hopes to scrub more carbon from the atmosphere than it has emitted since its founding in 1975. (Disclosure – My wife works in an unrelated capacity at Microsoft.

Microsoft has committed $1 billion to carbon reduction and removal technologies in order to achieve that goal and jump-start a global economy. According to the Intergovernmental Panel on Climate Change (IPCC), massive carbon removal is necessary to limit global temperature rises to 1.5 degrees Celsius. However, most technologies that can remove carbon from the atmosphere are still in development or too expensive to scale up.

What is available today are approaches that rely on nature—mostly trees, which absorb CO2 as they grow. All over the globe, voluntary programs are encouraging polluting businesses worldwide to pay forest owners to either grow more trees or keep existing trees alive. These programs are often not subject to government oversight. Microsoft has been open about its efforts to find acceptable options, especially.

In the journal last fall NatureWillmott Co-authored an editorial detailing Microsoft’s experience after it solicited greenhouse gas removal ideas. The company received 189 pitches. Combined, the proposals claimed they could remove 170 million tons of CO2—about three times what New York City produces each year. Most of that would have been taken up by forests.

Few of the pitches could withstand scrutiny; only 2 million tons of projects met Microsoft’s criteria for high-quality, long-lasting, and immediate carbon cuts. “Today, there’s simply not a lot of really secure forest carbon projects,” Willmott says. “We see a problem with that across the U.S. and across the world.”

She’s not alone in her skepticism. The non-profit journalism outfit will be in 2019 ProPublica conducted a study on South American forest offsets and found projects frequently did not offset as much CO2 as promised—if the carbon value could be substantiated at all. Bloomberg also pointed out in a series of stories that some offsets may not be as effective as promised. CreditFor “protecting” forestsThat aren’t actually threatened, which may be good for wildlife or biodiversity but doesn’t alter the land’s carbon balance. Some offsets have led to carbon “leakage”—even if an offset legitimately protects trees from logging, trees may get cut elsewhere to supply the same markets, resulting in no discernible climate benefit.

Finally, forest offsets suffer from a mismatch of timescales. The carbon emitted by burning fossilfuels remains in the atmosphere and harms the climate for thousands upon thousands of years. But the benefit of storing CO2 within trees is temporary because trees die. California’s offset program, which allows polluting companies to offset a small amount of their emissions by purchasing credits from forests in any state, requires sellers to demonstrate that carbon will stay locked in trees for 100 years—a long guarantee by international standards.

However, the program has its own benefits. Criticism received. ProPublica reported last year’s data MIT Technology ReviewBased on A previous study byCarbonPlan revealed that the state may have Let landowners take control of carbonstorage of millions of credits. Grist, an environmental news website, reported last fall on the state of the environment. Relying on haphazard projections regarding fire risk.

Regulators at the California Air Resources Board, which runs the offset program, are quick to point out it’s the only one in the United States linked to a mandatory statewide effort to cut emissions. The state requires businesses to reduce their emissions directly.

They also highlight the ecological benefits of offsets. “It’s creating a mechanism for the protection of forests,” says Matthew Botill, division chief for the state’s cap-and-trade program. But the question remains of how well it protects climate—especially as threats to forests grow.

How much insurance do you need?

Despite a lifetime spent in the woods, John Davis had rarely seen a bigger blaze than Oregon’s Bootleg fire. The vice president at Green Diamond would not normally have considered his company’s Klamath East lands a major wildfire risk. His trees were young, and often spread far apart. It was cheaper to let the trees grow older than to log them right now, since he could sell carbon credits. However, the heat wave had just hit southern Oregon, which had been too dry. The deadwood was also thick on the stands of adjacent U.S. Forest Service lands.

“On average, the federal land is not in a healthy state—it’s overstocked,” Davis says. “There’s a high level of fuel loading.”

His team spent many weeks responding to the blaze. But the fire produced smoke clouds that reached 40,000 feet. The front continued for miles. At one point, the swirling winds produced a tornado. When the fire picked up in the afternoons, “all you could do is back off until it laid down,” Davis says.

Green Diamond will have to wait at least until the summer to begin a comprehensive inventory to determine how much carbon was actually lost. Recognizing that unplanned losses will sometimes happen, California’s offset program builds in a backup plan. It requires offset participants contribute carbon credits towards a state insurance system called a buffer pool.

Landowners must reserve 2 to 4 percent for fire risk; 3 to cover insect or disease losses; 3 to cover weather risks like droughts and windstorms; and up 9 percent for human risks. On average, Credits from 17 to 19%They end up in the buffer pool and are then retired if there is no carbon.

But many scientists worry it’s not enough. Climate change is already causing unprecedented damage to forests. In the Sierra Nevada up to 19% of adult giant silvioias, which many of them have stood since Aristotle’s time, were killed in fires during the last two summers. Five of the eight largest tree species in the West have seen their numbers decline significantly since 2000. This data was compiled using satellite data, archival records and machine learning. Jon WangThe University of California, Irvine determined that California lost nearly 7 percent of its tree canopy between 1985 and 2021.

The Bootleg fire was still on, but a study was underway Publication by the American Geophysical Union showed that California’s forests are likely to decline in the future even under moderate climate-change scenarios—and that offset projects in California are located in “disproportionately vulnerable parts of the state” where risk of losses are “They are remarkably high and significantly undervalued.”

Yet California’s offsetInsurance pool, which so far includes forest projects in 29 states, does not weigh risk of fire or drought differently by region, Anderegg wrote in Science2020—even though risk is far greater in the West than, say, in New England. It is becoming increasingly difficult to quantify risk anywhere. For example, Texas’ 2011 drought claimed the lives of 301 million trees. This was one of 16 Texas counties. “No one predicted that,” says tree physiologist William Hammond, at the University of Florida. “It seems like every time one of these broad-scale events happens, the local ecologists are shocked.”

Hammond should be aware. In a study Published last monthHe identified 675 instances of tree death worldwide using 154 studies. He also tracked down the climate conditions that precipitated these deaths and their exact locations. “What I want everyone to get is that this is coming to a forest near you—and sooner than you think,” he says.

“The big, big question here is, ‘What should that buffer pool look like, and is the current pool adequate?’” Anderegg says. “We have a lot of signs that it probably is not.”

Shelby Livingston, a manager with the offsets program for California’s Air Resources Board, says she remains confident. The pool is growing with more projects. “When we do a protocol update, we will take into account the latest science and make any necessary adjustments,” she says.

But Anna Trugman, an assistant professor at the University of California, Santa Barbara, says she’s not quite sure how. “I’m a forest ecologist and thinking right now on a 100-year time scale of what forests will look like—it’s really hard,” she says. “‘Best science’ can’t tell you what this buffer pool should be. You’d need some infinite fudge factor.”

Burning the buffer

CarbonPlan scientists conducted their latest investigation partly to answer these questions.

California had issued around 190 million forest credits by the end of last year. Each forest credit represented one metric tons of carbon. About 30 million of those were in reserve to provide insurance for the buffer pool. Since the state’s program began, at least six major wildfires have struck lands representing carbon credits. Two of these fires have already resulted in the state renouncing 1.1 million credits. The state has not yet received independent assessments of the carbon loss from the remaining four fires.

CarbonPlan conducted its own analysis. They used state records of carbon stocks for each offset and standard metrics from the Forest Service to estimate carbon loss after fire. They also included accounting for carbon stored in wood products made of dead trees logged after the fire. They estimated that the fire loss from offsets in the first ten years of the program was already between 5.7 and 6.8 million metric tonnes. This represents 95 percent of all fire-related contributions to buffer pool.

“That means we messed up our calculations so badly that in less than 10 years we’ve blown through 100 years of credits,” says Danny Cullenward, policy director for CarbonPlan.

His team used a different approach to assess disease risk. Phytophthora ramorum,The invasive pathogen that causes sudden Oak Death has already killed more than 40,000,000 trees in California and Oregon. Tanoak, a native tree to the coast, is most affected. CarbonPlan found that 20 offset projects hold roughly 14 million tons of CO2 in tanoak—and that anywhere from 4.7 to 9 million tons of that could be lost to PhytophthoraIn this century. This would be between 82 and 159 percent of buffer pool that is earmarked for all forest diseases and insect infestations.

CarbonPlan research was published in a preprint. It has not been peer-reviewed. However, the work was reviewed by several experts. National Geographic. Daniel Sanchez, who runs the carbon removal laboratory at the University of California, Berkeley, calls it “a robust analysis that answers an important question.”

Whereas the study’s assessment of fire risk was based on a tally of actual events, the projection of disease risk is a projection, says Matteo Garbelotto, director of the University of California, Berkeley’s forest pathology lab. “But the take-home message from the research is for-sure correct,” he says. “Within 100 years, it is more likely than not that most of those areas will see the arrival of sudden oak death. And in five, or at maximum 10 years, 80 percent of the tanoak will be dead.”

Max Moritz, a wildfire specialist with the University of California Division of Agriculture & Natural Resources, says it’s not clear how representative the last few intense fire seasons will be of the future. But “even if the authors have very large uncertainties around their estimates,” Moritz says, “the lack of what is needed for 100 years of ‘permanence’ appears to be a serious challenge.”

California state officials declined comment until the research had been peer reviewed. But they pointed out that credits are pooled precisely so that losses from fire, for example, don’t necessarily have to be paid out Only from the credit that was paid in to cover the fire. They just come out of the overall buffer pool—which will grow as new offset projects are added.

But each of those new projects would need to reflect a very different assessment of risk, or “adding new projects only makes the problem worse,” Cullenward says. “You can’t pay off old bad debt with new bad debt. That is the very definition of a Ponzi scheme.”

For now, all eyes are on Green Diamond as officials await assessment of last summer’s losses. Microsoft already believes that fire risk is underweighted, based on previous experience. “We are in the universe of imperfect solutions here,” says Rafael Broze, carbon program manager at Microsoft.

Green Diamond is working to recover carbon. Last week, workers were already out replanting, sowing 1.3 million trees.


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