Are Wildfires Offsetting Progress in Carbon Reduction?

For nature lovers, the sight of a wilderness forest in flames is heartbreaking. While those who study forest ecology might share their sense of loss, they see something more: a natural phenomenon essential to long-term forest health.

A recent paper on the impact of California’s 2020 fire season from researchers at UCLA reported that “emissions in 2020 essentially negate 18 years of reductions in greenhouse gas emissions from other sectors by a factor of two.” In a communications ecosystem built around head-turning news, this finding spread like wildfire itself.

“One of the key points that we wanted to raise is that we really need to start tracking this and treating it as though it is at least a partial human emission source,” said Michael Jerrett, chair of the Department of Environmental Health Sciences at UCLA’s Fielding School of Public Health and lead author of the paper. “There are human fingerprints all over these fires.”

The California Air Resources Board (CARB) does track emissions from wildfires, says Dave Clegern, CARB’s public information officer. Its current draft scoping plan includes emissions from fires among the sources to be mitigated as part of the state’s overall climate strategy, though as a “natural” source.

This isn’t the first time equivalences between fire emissions and those caused by humans have been put forward, says Max Moritz, a wildfire specialist for the University of California’s Cooperative Extension based at U.C. Santa Barbara. In 2008, for example, California’s U.S. Rep. Kevin McCarthy claimed that fires produce more emissions than cars.

For those who study fire, this kind of talk lands as vilification of an essential natural process (if not timber industry messaging), Moritz says. He doesn’t deny the basic notion that more carbon in the atmosphere is not desirable but cautions that equating wildfires to fossil fuel emissions brushes over the nuances of forest ecosystems.

Trees vs. Tailpipes

Carbon embedded in forests has been drawn down from the atmosphere to fuel plant growth. Fires do result in carbon emissions, but as burned forests regenerate, they take carbon back to help them return to life.

The same can’t be said of an automobile tailpipe or an industrial smokestack. The carbon they emit has been pulled out of storage in the Earth’s crust, and they have no further use for it after they send it into the atmosphere.

The UCLA researchers acknowledge this difference. But they question whether carbon uptake from regeneration will happen fast enough. It’s unlikely, they say, that regrowth will occur “on the time scale necessary to meet near- and medium-term emission targets needed to avert passing the 1.5 degree C threshold.”

In a chapter of his 2021 book Smokescreen, fire ecologist Chad Hanson discusses changing perceptions of the “carbon bomb” emanating from forest fires. Estimates of emissions from fires tend to be based on models rather than field work, he says.

A paper published in 2019 by researchers at universities in Idaho, Utah and Colorado noted that such models assume forests are burned to the ground, while field observations indicate that less than 5 percent of mature tree biomass is burned. As a result, they say, estimates of emissions could be exaggerated by more than 80 percent.

A study Hanson and colleagues conducted in areas burned in California’s 2013 Rim and 2020 Creek fires found that even in areas that burned severely, less than 2 percent of the above ground biomass of live trees had been consumed.

“It's pretty common for forests to recoup the amount of carbon that was emitted within less than a decade after a fire,” says Hanson. The UCLA authors don’t include reabsorption from vegetation in their estimates, expressing the view that it could take “decades or longer depending on the type of ecosystem that burned.”

None of this negates the importance of their call for improving forest stewardship, or the need to better understand the relationships between wildfires and climate change — especially, the “wrong” kinds of fires.

The Right Kind of Fire

Natasha Stavros directs the Earth Lab Analytics Hub at CIRES, a research partnership between the National Oceanic and Atmospheric Administration and the University of Colorado. She has also worked with NASA and the Forest Service to understand the impacts of fires. “My interest is doing research that informs decision-making so that we can live more sustainably in the world with fire, which is inevitable,” she says.

Not only is fire inevitable, many forest ecosystems in the West need fire to be healthy. Some conifers will not propagate unless the heat of fire opens their cones so they can drop their seeds.

A burned forest is more ecologically rich than an old-growth one, says Hanson. “Fire is intrinsic in forests; they'll actually lose their productivity and carbon sequestration capacity slowly over many decades without it.”

Large-scale fires are not new. In fact, in the last 200 years there is a deficit of burned biomass compared to averages over the past 3,000, notes Stavros.

Human efforts to suppress fire, a departure from strategies native people used to maintain forest health, have changed forest dynamics and made “megafires” more likely. The kind of fire that could maintain forest health is now largely restricted to forests where humans have not attempted to halt the course of burns caused by lighting.

Fires that occur in the interface between humans and wildland, whether within forested areas or foothill communities adjacent to chaparral vegetation, have different dynamics. They present imminent risk to human lives and come with an imperative to protect homes and infrastructure often comprised of materials that can make fires worse.

“What we’ve seen in post-fire images of burned neighborhoods is that a lot of the trees around the shrubs and the homes are still green and unburned,” says Moritz. “The homes became the fuel and carried the fire through these neighborhoods.”

Each of these fire scenarios has its own set of solutions, and some of the most important depend on changing current patterns of human behavior.

Building a Culture of Stewardship

Humans are by far the most immediate threat to forests, and not just because they manage them poorly. A paper from the director of Earth Lab that looked at 1.5 million government records from fires between 1992 and 2012 found that humans started 84 percent of them and caused a fire season three times longer than the lightning-caused season.

One way to reduce this toll is to restrict development in fire-prone areas, a strategy emphasized by Jerrett and his colleagues. This includes not placing power lines in remote, fire-prone areas.

Hanson advocates increased funding for patrols where wildlands and human habitation interface. This can be bolstered by outreach and education campaigns that help residents better understand the kinds of behavior that can start fires, and the outsize role that people living in landscapes they love are playing in destroying them. Moritz points to the practice of restricting public access to landscapes during periods of extreme fire risk as a tool that could be used more often.

The materials and techniques to make buildings that will survive fires are firmly established. Building codes can ensure they are utilized in communities at risk of fire incursion. Recent federal infrastructure legislation has created opportunities to advance this work.

Undoing the consequences of decades of fire suppression is another challenge with a nuanced solution. Prescribed burns mimic natural forest ecology, and Stavros observes they can be planned for days with favorable weather conditions. The cultural fire management practices of native Americans were grounded in low-intensity burns.

“Thinning” forests to reduce the fuel in them is the approach most often advocated at state and federal levels, but it has potential to devolve into an open door for profiteering by lumber companies.

Removing small diameter trees and surface fuels can protect older, more valuable and more fire-resistant trees, but this has little allure to commercial loggers. In some cases, Moritz says, a trade-off is made by allowing larger trees to be taken to offset the cost of restoration.

Hanson has campaigned against mechanical thinning, especially clear cutting, and actively collaborates with others in the research community to gather evidence that it damages forest ecology.

Moreover, he says, more than 70 percent of the carbon in harvested trees is emitted into the atmosphere when biomass not used in lumber products is burned for energy. In this case, the nutrients that remain are in an ash pile, not on the forest floor.

“We’re going to need to reduce our consumption of wood products, and shift to greater recycling and non-wood alternatives,” Hanson says.

Fires and Climate

There’s no question that climate change and fires are interlinked. Dealing with them has become integral to planning for resilience in a warming world. A recent report from the United Nations Environment Program warns that the likelihood of extreme fire conditions will increase by as much as 57 percent by the end of the century.

But where do worries about fires fit into the broad effort to mitigate warming?

“As long as we have fire that is operating within natural bounds, we don't have to worry about carbon storage in the forest, or fire as a significant source of emissions because it's always going to be counteracted by regrowth and then some,” says Hanson.

Building consensus and understanding around what “natural bounds” might be has yet to be accomplished. Few look at Yosemite burning and think “fire deficit.”

“If it weren't for the fact that we had sprinkled people in homes and communities throughout flammable landscapes, we would probably feel differently about fire,” says Moritz.

Protecting landscapes and communities from fire may be more difficult because of climate change, but as much as Stavros is dedicated to preventing high-risk fire events, she doesn’t see this work as a path to climate mitigation.

“We're not going to meet our goals if we don't cut greenhouse gas emissions from fossil fuels — full stop.”

Editor's note: An earlier version of this article stated that the California Air Resources Board includes wildfire emissions in its greenhouse gas inventory. The article has been updated to say simply that CARB tracks them.