The acrid smell of charred wood still permeates the air as Sasha Berleman, a fire ecologist, and I walk along a dirt path up through the middle of a canyon in the Bouverie nature preserve in Sonoma Valley. On the left side, the earth is black as tar, and scorch marks as tall as a person scar the trunks of the mature oak trees scattered throughout the field. But on the right side, the ground is tan and brown, and you have to look hard at the still-green oaks to see any evidence of the fire that raged through here just a few weeks before. It’s no mystery to Berleman why the fire behaved so differently on the two sides of the trail at Audubon Canyon Ranch’s Bouverie Preserve. When flames hit the field on the left of the path, they met a dense wall of thigh-high grass that hadn’t been mowed, grazed or burned for 20 years. The flames must have been 5 or 6 feet tall. On the right side, however, Berleman had set a prescribed burn just this spring. So when the October wildfire hit, patches of fire blazed, but with so little fuel, the flames remained only inches high.
For more than a century, people have been snuffing out fire across the West. As a result, forests, grasslands and shrub lands like those in the Bouverie reserve are overgrown. That means that, when fire escapes suppression, it’s more destructive. It kills more trees, torches more homes and sends far more carbon into the atmosphere, contributing to climate change.
The devastating fires that hit Bouverie and a large swath of Northern California’s wine country in October killed 42 people and destroyed nearly 7,000 buildings. In California’s Sierra Nevada in recent years, megafires have burned at much greater severity than those forests ever saw in the past, killing trees across large landscapes and unleashing enormous quantities of carbon. The remedy, Berleman and many other scientists say, is to reintroduce fire to the landscape by allowing more natural fires to burn and setting controlled burns when weather conditions minimize the risk of a catastrophic blaze.
“We have 100 years of fire suppression that has led to this huge accumulation of fuel loads, just dead and downed debris from trees and plant material in our forests, and in our woodlands,” says Berleman. “As a result of that, our forests and woodlands are not healthy, and we’re getting more catastrophic fire behavior than we would otherwise.”
Addressing the problem will require a revolution in land management and in people’s relationship with fire — and there are signs both may be beginning.
As a child in Southern California, Berleman was deeply afraid of wildfire. But at community college, she learned that Native Americans used fire for thousands of years to manage forests and grasslands and protect their villages. Tribes regularly burned California’s oak woodlands, for instance, to remove underbrush and fight pests. It helped them spot prey more easily, keep weevils out of the acorns they gathered for food, and safeguard their homes from wildfire. In 2009, Berleman transferred to the University of California, Berkeley to study fire ecology. There, she worked on her first prescribed burn. “I instantly fell in love with the ability to use fire in a positive way to accomplish objectives,” she says. She trained as a firefighter so she could put fire to use as a land-management tool.
Sasha Berleman in the Bouverie Preserve after the massive wildfire raged through in October.
Two years ago, while she was finishing her doctoral dissertation, she began working part-time at Bouverie. Last fall, she presented her boss with suggestions for using fire to restore overgrown landscapes, both at Bouverie and across the North Bay Area region. He approved, and Berleman, 28, started as a full-time fire ecologist in January, set her first burn in May and began organizing a taskforce to conduct burns and train local crews.
She knew how fire-prone the region is. Still, the big blazes in October caught her by surprise. “I thought I had more time to get work done,” she says.
High winds played a big role in spreading the California wine country’s deadly fires. But Berleman and other fire ecologists believe overgrown grasslands, forests and woodlands contributed as well. “I’m more certain than ever that there’s a lot we can do between now and the next time this happens to make it so that the negative consequences to people are nowhere near as dramatic.”
When fire hits overgrown wildlands, it burns hotter and is much more likely to kill stands of trees and threaten property and people’s lives.
But it also unleashes the carbon held by trees, other plants and soil. Forests store enormous amounts of carbon — more than double the greenhouse gases in the atmosphere — and continuously soak up more, blunting the impact of all the greenhouse gases released by burning fossil fuels in power plants and cars. In recent decades, the size of fires, their intensity and the length of the fire season have all grown dramatically. The more destructive a fire, the more carbon it releases. In fact, largely because of fires, California’s forests emitted more carbon than they soaked up between 2001 and 2010, according to a 2015 analysis by National Park Service and UC Berkeley scientists. “After 100-plus years of fire suppression in forests, we’re seeing a lot more tree-killing wildfire,” says Matthew Hurteau, University of New Mexico fire ecologist and associate professor. “That has substantial implications for the carbon put back into the atmosphere.”
Further complicating the picture is climate change — the major factor behind the longer fire seasons and bigger fires. This creates a feedback loop, where megafires exacerbate climate change, which then encourages even bigger wildfires. One study found that from 1984 to 2015, climate change doubled the area burned by wildfires across the West, compared to what would have burned without climate change. As the globe keeps warming, scientists expect forests to continue getting warmer, drier and more flammable. Unless people reduce greenhouse gas emissions, climate change will significantly increase the frequency of wildfires. One study projected that if fossil fuels remain the dominant source of global energy and greenhouse gas emissions keep rising, by 2085 the acreage burned by fire in California will increase one-third to three-fourths. Elsewhere in the West, the size and frequency of fire is expected to increase even more dramatically. Until recently, intense fires were rare in the Greater Yellowstone Ecosystem. But one study predicted that with climate change, fire likely would become so common and widespread there that by the middle of this century, the region’s forests as we know them will vanish, replaced by other types of vegetation that may store far less carbon.
In California’s Sierra Nevada, the combustible combination of climate change and overgrown forests already is transforming landscapes and unleashing massive amounts of carbon.
A four-hour drive east of wine country, gray trunks of dead incense cedar and white fir cover the steep slopes of the Eldorado National Forest. Deep into a canyon and up to a ridge in the distance, the trees are so close together that their branches touch. UC Berkeley fire ecologist Brandon Collins brought me here to show me the consequence of decades of fire suppression combined with climate change. This forest would usually burn nine times over the course of 100 years, but no fire had blazed here since at least 1908. “Without fire, you’re going to have these dense stands no matter what,” Collins says.
In 2014, the King Fire hit this unnaturally overgrown forest, leaping into the canopy and racing across a vast landscape. Limited patches of high-intensity fire would be natural in these forests. But in 47 percent of the 97,717 acres burned in the King Fire, the blaze was so hot that it killed nearly all of the trees. This included 14 areas where rare California spotted owls were known to nest. Before people started suppressing fires, this kind of all-consuming blaze did not happen in this type of forest, according to tree-ring studies. “We have seen no evidence you could ever have gotten a mortality patch this big,” Collins says.
Brandon Collins, a UC Berkeley forest ecologist, amid trees in the Blodgett research forest, where fire scars from past controlled burns can be seen on trees that stand fairly clear of grass and underbrush.
The amount of carbon sent to the atmosphere from such an enormous fire is staggering. “It’s ugly,” says Collins. “It’s not only a huge initial loss just from the direct emissions, but it’s slow emission over time as these trees break and then fall to the ground and the decomposition process really gets underway. We’re looking at 30 years or 40 years of pure emissions coming from this area with very little on the uptake side,” Collins says.
Just the initial blaze released 5.2 million metric tons, roughly as muchgreenhouse gas emissions as 1.1 million passenger cars emit in a year, according to an estimate by Forest Service ecologist Leland Tarnay. It’s too soon to analyze the fire’s total carbon footprint.
It could take a long time for this landscape to start packing on carbon again. Though some trees’ cones require fire to reseed, these particular types of conifers won’t grow back because the fire burned their seeds. The silver lining is the native oaks, which are fire resilient and can resprout from roots or stumps, even after a trunk is killed by fire. Already, their seedlings are emerging from the sea of dead trunks.
The King Fire of 2014 burned in an area that hadn’t burned for more than a century. In almost half of the 97,000-plus acres affected, the fire burned with such intensity that it killed nearly all the trees.
USFS Rapid Assessment of Vegetation Condition after Wildfire, Composite Burn Index
Nearby, some strips of trees are still green. Their trunks are also more broadly spaced. In these areas, the Forest Service had set prescribed burns or thinned the forests by logging some trees. Forest Service surveys show the King Fire burned much less intensely in these areas. Flames were lower, staying on the forest floor rather than surging into the canopy of the trees. Firefighters used these areas to slow and stop the fire. More trees survived.
Just a few minutes’ drive from where the King Fire raged, Collins shows me where he and other scientists have been studying how people can help restore forests to more natural conditions. Thanks to firefighters’ efforts, UC Berkeley’s Blodgett Research Forest narrowly escaped the King Fire. Blodgett was clear-cut in the early 1900s, before the university took it over. After 100 years, it’s grown into a lush forest ofincense cedar, ponderosa pine, white fir and oak trees.
The first patch of forest Collins shows me is the control forest, from which fire has long been banned. The understory is so thick with small trees and shrubs that it’s difficult to walk; we have to step over tangles of dead trees and branches. If a fire were to strike this area, it would easily climb from the ground to the lower branches and up into the canopy. “And then it can really spread,” Collins adds.
In the next patch of forest we visit, loggers cut down and sold some of the medium-sized trees in 2002. Then they shredded the small trees and underbrush using a big machine called a masticator, and spread the remnants on the forest floor. Now, the trees are widely spaced; sunlight shines through the canopy. The High Sierras are visible in the distance. If a fire were to come through here, Collins says, it likely would stay on the ground, and wouldn’t harm the trees or emit much carbon.
In another plot, crews set prescribed burns in 2002 and 2009. Scorch marks blacken the thick bark of some trees, but they’re still healthy. The forest is open, but more variable than the thinned forest. In one patch of tall ponderosa pines, the fire blazed hotter than in the rest of the forest. Several big trees were killed, leaving the kind of snags that woodpeckers love. This plot would also be likely to do well in a fire, Collins says.
A fourth plot shows some of the pitfalls of combining thinning and burning. Crews cut down some trees, shredded the noncommercial wood and scattered it on the forest floor. Shortly afterwards, they burned the forest. The fire burned so hot from all the wood on the ground that the remaining trees were injured. They haven’t grown or soaked up much carbon since.
An untreated area at greater risk of severe fire
Overall, the experiments at Blodgett suggest that prescribed burns and thinning can have long-term carbon benefits. But in the short term, carbon emissions will increase. Neither the burned nor the thinned plot has caught up with the carbon stored in the forestthat was left alone. But with less competition, the trees are growing faster in the thinned and burned plots, and Collins predicts that eventually they will store more carbon than the denser stand.
Scientists have seen a similar pattern in another experimental forest in the Sierra Nevada — Teakettle, an old-growth forest with giant sugar pines. As in Blodgett, the forests initially stored less carbon after being burned or thinned. But the forests at Teakettle recovered their carbon stocks more quickly than Blodgett did, in about seven years. “If you restore forests, you do knock downthe total amount of carbon, but you prevent very large tree-killing fires. Over time, the carbon stored in the forest is much more stable because you’ve taken steps to prevent big hot fires from occurring,” says Hurteau.
The old-growth trees in Teakettle soaked up carbon faster than Blodgett’s younger trees. But in both types of forests, carbon should accumulate faster in fewer big trees. And the thinned and fire-opened stands make big trees healthier by reducing competition for water and nutrients. That improves their odds in both fire and drought. Big trees are generally more fire resistant, meaning they’re more likely to survive a fire and continue to soak up carbon afterward. “If we want to maintain this ecosystem service of removing carbon from the atmosphere that trees provide, we need to make investments in doing what we can to protect the big trees, because they’re doing a disproportionate amount of the work,” says Hurteau.
A single tree that is 6 feet in diameter, like one of the big sugar pines in Teakettle, holds as much carbon as 60 small trees, 8 to 10 inches in diameter, says Malcolm North, a leading Forest Service fire ecologist and Hurteau’s colleague and former teacher. That’s a much more reliable way to store carbon. “The carbon in the big trees is a secure investment like gold,” North said, whereas the carbon stored in overgrown forests is more like “junk bonds.”
Despite the science, however, forest managers continue to snuff out most fires. For the decade ending 2008, the most recent data collected, only 0.4 percent of ignitions were allowed to burn as managed wildfires, North, Collins and other fire ecologists wrote in 2015 in the journal Science. “Changing climate and decades of fuel accumulation make efforts to suppress every fire dangerous, expensive, and ill-advised,” they wrote.
North was reprimanded for the article and forbidden to talk with the media for a year. But he’s speaking out again, because the dire consequences of overgrown forests are becoming so clear.
North says thinning is not a solution for much of the Sierra Nevada. Only 28 percent of the landscape can be mechanically thinned, he calculated; the rest is too steep or remote. “You cannot thin your way out of the problem,” he says. “You’ve got to use fire.”
Official Forest Service policy has acknowledged this. The 2014 interagency National Cohesive Wildland Fire Management Strategy calls for expanding the use of prescribed burns and letting more wildfires burn. “It’s just not being followed; that’s the real problem,” North says. “Everyone knows what we’ve got to do. But it’s not being done.”
Sasha Berlemen encountered that stubborn resistance to letting fires burn this summer, when she was on a Forest Service hotshot crew. She fought fires in Plumas, Six Rivers, Modoc and Klamath national forests. Fire managers were aggressive, often sending her crew to the fire’s edge to try to prevent it from spreading. That contradicted what she learned in her fire ecology classes about letting wildfires burn larger areas. “There’s this disconnect that I didn’t know about until summer — between what everyone is saying in academia and what’s actually happening on the ground,” she says.
Some forest managers have begun to accept more fire, however, as have national parks. The 2013 Rim Fire, the biggest fire in Sierra Nevada history, burned at lower intensity in parts of Yosemite and Sequoia national parks than it did in national forests, killing fewer trees and producing less air pollution. The parks had previously allowed wildfires to burn when weather conditions, such as light winds, minimized risks.
The Forest Service has been more reluctant to let natural fires burn, in part because of checkerboard land ownership and because houses have been built in many forests on private property inholdings. “Ecological benefits don’t have a huge voice,” Collin says. “No one will sue for not letting fire burn. If you let a fire burn and something bad happens, someone will sue you.”
Air-quality regulations play a role, too. Both North and Collins tried for weeks to schedule burns this fall. Air quality concerns and a lack of available personnel — the wine country fires were still raging — delayed their burns. Both finally were able to burn at the end of October. “The Forest Service is cursed with lands with houses in middle of them, wildland-urban interface where people don’t want to breathe smoke,” North says. “Almost everything works against trying to work with fire. The only way it’s going to change is to get public support.”
Craig Thomas, conservation director of Sierra Forest Legacy, has been calling for more natural and prescribed fire in the Sierra for two decades. He believes that after the Rim, Rough and King fires, the public and policymakers better understand the threat of unnaturally overgrown forests. “They jarred California society in a big way,” Thomas says. “This disaster is a human creation; climate change is making it even tougher.”
In 2015, the Sierra Forest Legacy, the Forest Service, CAL FIRE, the state fire agency, and other agencies and groups signed an agreement to use more fire in wildlands management and increase training for fire managers and crews. Since then, the Forest Service has increased the total acreage where it has allowed natural fires to burn from an annual average of about 10,000 acres to 247,000 in 2016 and 130,000 this year. “That was a big jump,” says Rob Griffith, assistant director of the Forest Service Pacific Southwest region’s fire and aviation program.
Prescribed burns are up, too, from 20,000 acres on average before the agreement to about double that in 2015, 2016 and 2017. Some 96,000 acres of prescribed burns are scheduled for the next fiscal year, Griffith adds.
California’s commitment to tackling climate change is giving extra oomph to efforts to bring back fire. For instance, funding for the research at Teakettle and Blodgett comes from revenue from the state’s cap-and-trade program. The state auctions allowances, which big polluters buy to receive the right to pollute. California doesn’t want the progress it’s making from switching to electric vehicles and renewable energy to be nullified by giant pulses of carbon released by wildfires.
Still, Berleman thinks it will take a revolution to get people to overcome their primal fear of fire. She knows how hard it is. She grew up in Temecula, an inland city between Los Angeles and San Diego, in a valley surrounded by chaparral-covered hills that burned nearly every year. When she was 4, she stood in her yard and caught ash in her hand and watched ash cover her lawn like snow. “I was afraid of fire,” she says. “I remember having night terrors that I’d have to try to save my family from wildfire.”
But her view has changed since then, and she hopes others can change their minds, too. She thinks the October fires will be a catalyst for policymakers and the public to accept that fire is the best protection against megafires and all the carbon they emit. They already have emboldened her to move quickly than she had planned to introduce fire to parts of the North Bay Area that escaped the October fires.
“Now that this has happened, we’ve decided the wake-up call has already happened,” she says. “We need to scale up if we’re going to get though this; it’s going to take all hands and all lands.”
She now plans to apply fire in five counties instead of just two. And instead of burning just grasslands, which produce far less smoke, she’ll burn forests and woodlands as well. If people push back, she knows what she’ll say: “By being afraid, we’re making our problem worse. There’s another option. That fear can actually inform a positive movement; you can take a fear of fire and decide, ‘OK, we don’t want megafires; we’re afraid of them.’ Let’s take action instead. Fire could be our favorite tool on our landscape, and we could have more beautiful and healthy landscapes. And people wouldn’t have to live in as much fear.”
Elizabeth Shogren is a reporter for Reveal, covering science.
Climate Desk is a journalistic collaboration dedicated to exploring the impact—human, environmental, economic, political—of a changing climate. The partners are The Atlantic, Atlas Obscura, CityLab, Grist, The Guardian, High Country News, HuffPost, Medium, Mother Jones, the National Observer, New Republic, Newsweek, Reveal, Slate, Undark, Wired.