The Era of Fire
How a hotter world is changing the West
A version of this article appears in the Summer 2025 Sun Valley Magazine
Beaver Creek, Camp, August Complex, Dixie, Park, Durkee—all innocuous enough sounding place-names—but words now burned into the Western lexicon. While just a handful of the thousands of wildfires that burn across the 11 Western states each year, they have come to represent wide-scale destruction and a changing world. Forest fires are, literally, as old as the hills, but talk to firefighters, incident commanders, and researchers and they will all tell you that this is different. Fires are bigger, more frequent, and more severe than in years past. The fact is the era of fire is upon us.
Ronnie Abolafia-Rosenzweig, a researcher at the National Center for Atmospheric Research, led a 2022 study of fire activity across the Western states using satellite data that has been gathered since 1984. On average, the annual burned acreage has increased 3.6%, or about 104,000 acres every year. And because averages can sometimes hide more dramatic trends, Abolafia-Rosenzweig further analyzed the study period and split it in half, looking at fire activity between 1984 and 2000, then comparing it to fire activity between 2001 and 2018. In the first period, 27.4 million acres burned. In the latter period of years, the burned acreage more than doubled to 55.9 million acres.
And though it may seem intuitively obvious, the nature and intensity of bigger fires has also changed. In his book, “Fire Weather,” John Vaillant details the catastrophic 2016 Fort McMurray fire in Alberta, Canada, that burned 1.5 million acres, displaced 90,000 people and caused an estimated $4 billion in damages. The temperature at the fire front reached 1,000 F, causing violent updrafts of hot air, smoke, and toxic gases that reached 30,000 feet into the stratosphere. With the updrafts came equally violent downdrafts on the outer edges of the rising column. The downdrafts acted like a giant fan, pouring oxygen on to the inferno.
Another phenomenon at Fort McMurray—only observed and identified in fires of the last 25 years—was that of fire-generated lightning and hailstorms. As the mix of soot, water, hot air and other gases reaches the stratosphere, it cools and condenses into hail and rains down. The violent updrafts can—as it did in Fort McMurray—also generate what is called a pyrocumulonimbus cloud (pyroCB), a thunderhead created by the fire. While fire embers can travel five miles or so with the right winds, a pyroCB can spread lightning, and therefore fire, 50 miles in any direction. As Vaillant points out in his book, these pyroCbs were witnessed in the previous century but were always associated with volcanic eruptions, not wildfires.
That the nature and scope of wildfires in the West is changing is not in dispute. The more pressing question is: Why is it happening?
Beth Lund joined the U.S. Forest Service in 1976 as a 20-year-old firefighter. At her retirement in 2024, she had risen to Deputy Director of Fire and Aviation for the Intermountain Region. She was also one of only 16 Type I incident commanders nationwide, those who lead and manage the largest and most complex wildland fire incidents. One of those major fires included the Beaver Creek fire in 2013 that ripped through the Sawtooth National Forest near Sun Valley, Idaho, burning nearly 115,000 acres.
In an interview prior to her retirement, Lund pointed to several factors that have changed since she began fighting fires. “The scope and scale of fires since the 70s has gradually grown…The number of people that are out in the woods started to increase because the population grew, so there were more human starts. And I think the forest health is definitely an issue … Really the root cause of forest health declining is fire suppression in and of itself … that’s probably commonly known … After the big fires of 1910, we went on this campaign to put everything out. ‘Put everything out by 10 a.m. the next morning.’ It was called the ’10 a.m. policy.’”
The U.S. Forest Service, established in 1905 by President Theodore Roosevelt and led by Gifford Pinchot, was charged with managing the public lands that Congress had designated as “forest reserves” in their Forest Reserve Act of 1891. These “reserves” later became known as national forests. While the original mission of the USFS was to ensure the nation had adequate timber supplies, as well as quality water sources, the Great Fire of 1910 shifted the organization’s focus.
The fire that raged through Idaho, Montana, and Washington burned nearly 3 million acres and killed 85 people, 78 of whom were firefighters. The scope of destruction took the country by surprise. Lawmakers doubled the Forest Service budget, and the organization refocused its efforts on “total fire suppression.”
In 1935, the then head of the Forest Service, Ferdinand “Gus” Silcox, formalized the suppression approach with the “10 a.m. policy.” It was a policy that was in place until 1978 and that inadvertently led to great build ups of fuel in the national forests. Forests became older, denser, and filled with dead and dying trees waiting to ignite.
Anyone who has gone camping or has a fireplace intuitively understands fire and what it takes to start one. But what exactly is fire? In short, it is a chemical reaction—one between oxygen and cellulose, which is the structural element of plants and trees. When wood (cellulose) is heated up to 572 F (its flash point), it releases hydrocarbon gases that react with oxygen to form carbon dioxide and water. Importantly, heat and light are given off in the reaction. In the fire world, the reaction is simplified into the “fire triangle,” in which fuel, oxygen, and heat form the three vertices. In fact, there is a fourth critical element—a chain reaction—that keeps providing heat, enabling the fire to continue. Some refer to this as the “fire pyramid.” The key fact about the pyramid, or the triangle, is that if just one of the elements—oxygen, fuel, heat, or the chain reaction—is taken away the fire stops.
To understand why fires have gotten bigger, more frequent, and more intense, one need only look at these variables. Clearly, the oxygen content of our atmosphere hasn’t changed over time. Granted, once a fire starts, a fierce wind can introduce more oxygen into a wildfire. That notwithstanding, no one has yet shown that the Western climate has become windier over the last century of forest fires.
Researchers have been able to show, however, that over time our forests have gotten hotter. In a 2018 paper “Climate Change and the American West,” John Abatzoglou and Lauren Parker reported that between 1895 and 2016, air temperature in the Western states increased 2.3 F, with the majority of that increase coming since 1970 and with four of the five warmest years coming since 2010. Hotter air temperatures generally mean drier air and, subsequently, drier fuels in the forest, which is measured by the metric “aridity.” Drier fuels are more flammable; as they have less water in them to act as a heat sink, they can more quickly reach their flash point.
Abatzoglou and another colleague, Park Williams, were able to show that between 1984 and 2015 forest fire area across the West increased exponentially with fuel aridity. What’s more, they showed that more than half of that increase in aridity was due to human-caused climate change. And in the years 2000-2015, climate change led to 75% more forested area experiencing high fire-season fuel aridity, as well as an average of 9 more days per year of high fire potential.
In a recent interview, Abatzoglou provided additional data through 2024 that continues to show the exponential relationship between increasing forest fire area and aridity.
The increase in hot, dry weather has other implications for forest fires besides drying out the fuel load. It can make forests more susceptible to attacks from insects and pathogens.
“The same factors that are facilitating chronic drying of vegetation that enable fire are being reflected in increased drought stress that can lead directly to mortality or aid in bark beetle impacts,” Abatzoglou said. “… Studies on bark beetle have highlighted three factors that favor outbreaks: one, lack of very cold winter temperatures that kill of beetle populations, two, warmer temperatures during the year that increase reproductive cycles, and, three, drought stress that weakens tree resistance to attack.”
Laura Lowery, an entomologist with the U.S. Forest Service, has studied mountain pine beetles and Douglas fir beetles extensively, particularly in the Sawtooth and Boise National Forests. She explained that these rice-sized beetles, like wildfire, “…are supposed to act as a disturbance agent in the forest.” The Douglas fir beetle, for instance, attacks only trees that are greater than 20 inches in diameter and that are under stress for one reason or another, be it drought, defoliation caused by a pathogen, or wildfire burn that has not killed the tree. Lowery said that the trees give off ethanol when stressed and the beetles can sense that. They will then communicate with each other via pheromones to attack a stand of trees. As beetles kill trees—it may take a thousand or more to kill a tree—they open up gaps in the forest that then lets in sunshine and allows new trees to grow. In this way, the forests become “resilient.”
“Where you run into problems is when you don’t have enough gaps in the forest and new trees aren’t growing and you get lots of old trees … and that’s where we are now,” Lowery said. “Through fire suppression over the decades, when we kept fire out … trees kept growing older and older.” The homogeneity of the forest becomes a vulnerability; large outbreaks are more likely to occur. And large outbreaks kill big swaths of forest, introducing still more dry fuel into the mix.
The dynamic works both ways. Lowery noted that after big fires—like the 2007 Castle Rock fire and the 2013 Beaver Creek fire in the Sawtooth National Forest—there are large numbers of trees under stress, either burned but alive or simply stressed by drought or pathogens such as dwarf mistletoe. And so, the beetles thrive, and, as happened in 2007 and 2013, much of the forest seems to turn pink and red with dying or dead trees, all of which become kindling for another big fire. A feedback loop sets in.
What can break the cycle, according to Lowery, is “an untimely cold,” a cold snap in early spring or fall. “But what the research is showing is that we don’t have enough cold in the winter to kill them (beetles) under the bark. Not like we did in the past … so that’s a difference from the early 1950s or earlier.”
What has also changed over time is the cost to suppress wildfires. The National Interagency Fire Center has tracked costs to suppress fires nationwide from 1985 through 2023. In 1985, that total cost was $679 million (in 2023 dollars), and $235 per acre burned. In 2023, the total cost was $1.96 billion, with a cost per acre of $545.
Although there is obviously variability in fire seasons from year to year, it turns out that the trend holds with averages. The average annual cost over the first 10 years of the span (1985-1994) was $932 million, with an average cost per acre of $322 (also adjusted for inflation). Averaging over the last 10 years (2014-2023), the annual cost comes out at $3.1 billion, with a per acre average of $509. It’s safe to say that costs, per acre and total, have increased by a factor of somewhere between two to three over the last 39 years.
Certainly, the tools, as well as the protocols, for fighting fires are more sophisticated than they were 39 years ago. Jake Renz, the North Zone Fire Management Officer (FMO) for the Sawtooth National Forest, is in his 20th year of fighting fires in the West. Since he started in 2005, much has changed, on both the fire side and the fire-fighting side.
“We’re definitely getting drier. We definitely have more people out there and there’s more interface,” Renz told me. “And the number of acres has increased. It’s due to a lot of factors: We’re trying to manage fires more now. And we have a different risk management process and decision making and responder risk tolerance. We’re really trying to manage exposure and responder risk, more so than in the past … Now, we don’t necessarily stick folks in the nastiest, gnarliest spots.”
A wildfire “start” can come in many forms but is categorized as either a natural start—lightning—or a human start, which could be from a campfire, cigarette, car tail pipe, or even arson. The Park fire in California, which burned 429,000 acres, was started by a man pushing a burning car into a ravine.
Surprisingly, the majority of big fires are caused by humans, not lightning. But as Renz pointed out, this may have more to do with timing. Humans tend to start fires when the weather is conducive to wildfire: hot and dry. “Generally, when a storm rolls through, there is usually moisture involved with it. The RH (relative humidity) goes up, the temps go down, and the fire doesn’t generally rip. It can, but there are definitely more single trees that we catch than 100,000 acres.”
A “start” might be reported by the public recreating in the forests, a backcountry pilot, or perhaps by a Forest Service-contracted night flight using infrared technology to spot heat signatures. To confirm the start, Renz and his team will do a reconnaissance flight via helicopter to determine if and how firefighters might access the area: can smokejumpers get in there, is there a landing zone for helicopters, is there road access for an engine crew?
If there is access, the next question Renz has to answer is: Are there critical values at risk? Generally, these are things humans have built or introduced into the forest: cabins, infrastructure, power lines, and the like.
As a fire grows, Renz and colleagues will start ordering up resources as appropriate and if available: Hot Shot crews, smokejumpers, helicopters, rappelling teams, retardant flights, and air tankers. When a fire gets to a critical level, a Complex Incident Management Team will be called in for a 14-day stint. This will be a staff of 90 that has the experience and qualifications to attack a large fire.
Of course, large fires in the West rarely happen in isolation and so present a dynamic and multi-front challenge. There are often several fires burning at once. And this is when the National Interagency Coordination Center (NICC), located in Boise, Idaho, comes into play. NICC will coordinate the mobilization of resources nationwide, depending on relative needs and availability. As the climate in the West gets hotter and drier, the fire seasons longer, the work of NICC has increasingly become a mad scramble to shuffle resources and personnel from state to state, fire to fire.
Often called the Second Industrial Revolution, the latter years of the 19th century were a time of roaring economic growth and development in the U.S. Railroads expanded West, telegraph lines went up, factories were built—extraction industries—coal, timber and minerals—flourished. When an assassin’s bullet ultimately ended the life of then President McKinley on September 14, 1901, not only did a new president take office, but a new era—the Progressive Era—took hold. Theodore Roosevelt was a Republican who deeply appreciated the Western forests for their aesthetic value, but he was also a politician who viewed them as the key to sustaining America’s growth through the timber they generated and the watersheds they protected. While deeply influenced by forester Pinchot and naturalist John Muir, Roosevelt single-handedly ushered into the 20th century the idea of conservation as a political and economic way forward for the world’s industrial leader.
A century and a quarter later, the forests that Roosevelt put in reserve for the American people—230 million acres and 150 national forests—endure as the living, breathing heart of the Western landscape, albeit with the imminent threat of a rapidly warming climate. Granted, all of life is predicated on evolutionary change; however, the changes the world faces now are orders of magnitude faster than biological, ecological, and, most importantly, political systems can adapt to.
Fire changed the course of human history once before. It may change it again.