Why Colorado’s Wildfires Are Growing More Severe
Written by Quentin Septer
Note: This is a modified excerpt from my book, Where Land Becomes Sky: Life and Death Along the Colorado Trail, available now.
The Hayman Fire began in the confines of a fire ring on June 8, 2002. The flames spread, igniting nearby debris and leaping to the crowns of surrounding pines. A perfect storm of drought, record high temperatures (at the time, anyway), and gusting winds fueled a 138,000 acre inferno. The fire jumped roads and clearcuts, into the southern corner of the Lost Creek Wilderness Area. The blaze was contained just south of the Colorado Trail. “Thus,” my guidebook states, “CT hikers will see little evidence of this catastrophe.” But we mountain bikers cycle straight through the heart of what remains of the Hayman Fire.
While the Hayman Fire blazed, a reporter asked then Governor Bill Owens what the scene looked like. “It looks as if all of Colorado is burning today,” Governor Owens replied. The Hayman Fire burned an estimated 500,000 trees, 600 buildings, and 133 homes. More than 5,000 residents were evacuated from the area. Smoke from the inferno could be seen nearly 200 miles away. Record high concentrations of particulate matter were recorded in Colorado’s atmosphere during the fire. One woman living in the nearby town of Florissant died from an asthma attack induced by the airborne debris. For more than a month, the Hayman Fire burned everything in its path: flora, fauna, soil, and civilization alike. Then the rain came. Tons of ashen sediment was washed from the landscape, carried off into the Cheesman Reservoir and the South Platte River. Rivers and streams ran brown and sludge-like with the debris. For years, Denver’s drinking water was impaired by the fallout, and the city still spends millions of dollars annually to combat lingering damages from the Hayman Fire. As for the fire area itself, what remains is a disturbed land of scorched trees and charred dirt, fired like clay in a kiln.
For years, the Hayman Fire was the largest wildfire in Colorado state history. It was an anomaly, a natural disaster, a freak event born of unfortunate circumstances. That is, until the year of 2020, when the blaze was surpassed in size by the Pine Gulch Fire, the Mullen Fire, the East Troublesome Fire, and the Cameron Peak Fire—all in one historic, record-breakingly terrible fire season. In 2020, more than 700,000 acres went up in flames across the state of Colorado. Fires burned well into December, once considered more than two months outside of the state’s fire season. In 2020 alone, more acreage of Colorado’s forests burned than in all of the state’s wildfires throughout the 1960s, ‘70s, ‘80s, and ‘90s, combined. But Colorado’s historic fire season of 2020 was years—decades, even centuries—in the making.
It all began around the tail end of the 18th century, when we human beings started burning coal and oil and other fossil fuels en masse, pumping otherworldly quantities of carbon dioxide and other greenhouse gasses into the atmosphere. Carbon dioxide, along with fellow greenhouse gasses, as I’m sure you’ve heard a time or two in your life, function very much like, well, a greenhouse in the airways of earth. When sunlight enters earth’s atmosphere, most of that light is absorbed by the planet’s surface. Some solar rays, however, are deflected back into the atmosphere and beyond, back into the cosmos. But as more greenhouse gasses have accumulated in earth’s airspace, more solar radiation has become trapped in our planet’s atmosphere. The energy has nowhere to go. Thus, it lingers in the form of heat. This process is known as “the greenhouse effect.” Plainly, the more fossil fuels we burn, the more greenhouse gasses we emit, the more solar energy we enclose in the airways of earth, and the warmer earth’s climate becomes.
Global atmospheric CO2 concentrations in the year of 1750 (just before the Industrial Revolution really started gaining steam) were at a relatively steady 280 parts per million (ppm). By 2020, this figure rose to 412.5 ppm. Over the same period, the average temperature of earth’s atmosphere increased by about 2 degrees Fahrenheit, according to NASA’s Goddard Institute for Space Studies. And warming continues to accelerate. Since 1975, humanity has emitted more greenhouse gasses than in all of the preceding years of our species’ existence, and roughly two-thirds of the planet’s warming has occurred in the last half century. Since the ‘70s, the planet has warmed at a rate of about 0.2 degrees Celsius per decade.
North America’s atmosphere in particular has been warming at a rate of 0.31 to 0.54 degrees Fahrenheit per decade since the late 1970s. In August of 2020, as I cycled my way along the Colorado Trail, the average temperature across the United States was about 2.6 degrees Fahrenheit above the 20th Century average, the nation’s third hottest August in recorded history. Colorado experienced the hottest August temperatures on record, as did a number of states across the American West.
Complicating matters, late summer in the western United States (the peak of the region’s fire season) saw not only heat waves, but drought as well. In August 2020, 94 percent of Colorado was in a dry spell, with about a quarter of the state’s drought characterized as “extreme” or “exceptional,” by the National Oceanic and Atmospheric Administration’s National Drought Monitor project.
This combination of blazing temperatures and an utter lack of precipitation effectively baked the region’s soil and vegetation, priming the landscape to burn. And these trends show no signs of slowing down in the future, either. By 2050, Colorado’s climate is projected to warm 2.5 to 5 degrees Fahrenheit relative to baseline temperatures recorded between 1950 and 1999. Accompanying these rises in temperature will be heightened risks of wildfire and more severe drought conditions. And if the planet warms only 2 degrees Celsius relative to average temperatures seen at the dawn of the Industrial Age, as is projected to occur this century, wildfires are expected to burn between four and eight times more land across North America every year. Oh, and by the end of this century, the United States faces an 80 percent chance of being hit with a “megadrought”—a drought lasting more than two decades.
As air warms and dries, vapor pressure deficits rise. Vapor pressure deficit (VPD) is the difference between water vapor pressure in the air of a given locale, and what the water vapor pressure would be at that place, at that temperature, at 100 percent humidity. The higher a region’s VPD, the thirstier the air becomes, so to speak, and the drier the region’s plants and soils grow. Water is quite literally pulled from soil and vegetation, up into the atmosphere, leaving behind a dry and flammable landscape.
Across the United States, vapor pressure deficits have been rising steadily since the late 1970s. “These trends are especially apparent in the southwestern United States,” environmental scientists Darren L. Ficklin and Kimberly A. Novick wrote in a 2017 paper, “which has shown to be especially sensitive to forest mortality from increases in temperature.” VPD measurements seen across California and much of the western United States in 2020 were “record-breakingly high,” in the words of Park Williams, a hydroclimatologist at Columbia University. And as air temperatures rise with a changing climate, these trends in VPD are projected to increase, too. By the end of this century, VPDs in the continental United States are projected to rise as much as 64 percent relative to measurements taken throughout the late twentieth century. In the Rocky Mountains, VPDs may rise as much as 200 percent by 2100. This drying of the region’s soil and vegetation is certain to increase the frequency and severity of future wildfires; to what degree, nobody can say with certainty.
Heightening complications brought on by heat, drought, and dry air, spring came early in 2020. And unusually warm, early springs tend to exacerbate the effects of drought and rising temperatures. Colorado’s statewide snowpack was slightly above average in the winter months of 2020, according to the National Resources Conservation Service. Come the spring and summer months, however, Colorado’s snows began to melt rapidly. By June, the state’s snowpack declined to about 70 percent of the historical average.
In the high country, snowpack heldover from the winter months provides ecosystems and wildlife with water and moisture as snow melts slowly, into the summer. Snowpack absorbs solar radiation, too, cooling local surface temperatures. But when that snow melts early in the year, and when that moisture evaporates—as it tends to do during warm, early springs—soil and vegetation absorb incoming sunlight instead. The air grows drier, and so too does the flora. Come fire season, the stage is set for wildfires to ignite. It’s no surprise, then, that more than 70 percent of North American lands charred by wildfire from 1970 to 2012 burned in the wake of unseasonably warm, dry springs, according to a paper published by the Philosophical Transactions of the Royal Society B: Biological Sciences in 2016. The 700,000 acres burned across Colorado during the year of 2020—in addition to much of the 10 million acres burned across the United States—can be added to that percentage.
A great deal of this can be summed up with some simple arithmetic: earlier, warmer springs plus longer, hotter summers equal longer fire seasons in Colorado and the rest of the American West. Since the 1970s, in fact, the western United State’s fire season has grown 84 days longer than fire seasons of yesteryear. Colorado’s 2020 fire season highlights this forlorn trend. Of the 700,000 acres of Colorado’s forests to go up in flames in 2020, nearly a third of this area burned during or later than the month of October, once considered well outside of the state’s fire season. (This trend, too, is highlighted by the more recent Marshall Fire, which burned from December 2021 into January 2022 and consumed more than 1,000 homes in flames in the towns of Louisville and Superior, just east of Boulder, Colorado.)
When seen through the lens of history, Colorado’s 2020 fire season displays still other disconcerting trends. Prior to the European settlement of North America, wildfires across the American West were typically low to mild-intensity burns, on the scale of a few dozen acres. Many of today's wildfires burn in the thousands of acres. In 2020, 80 wildfires burned across the state of Colorado, 25 of which exceeded 1,000 acres in size—what the United States Forest Service considers a “large” wildfire. Nine of these fires burned more than 10,000 acres, and four of these wildfires—the four largest wildfires in Colorado state history—set more than 100,000 acres ablaze. The Pine Gulch Fire: 139,000 acres. The Mullen Fire: 176,000 acres. The East Troublesome Fire: 192,000 acres. And the Cameron Peak fire, the largest wildfire to burn in Colorado to date, exceeded 200,000 acres in size. To put these numbers in context, Colorado’s wildfires burned a total of 106,000 acres throughout the 1970s.
And, of course, an added element in this story of intensifying wildfires across the American West is one of human error. In addition to pumping roughly 375 billion metric tons of carbon dioxide into the global atmosphere and warming the planet about 1.2 degrees Celsius, we’ve grossly mismanaged our forests with respect to wildfire. For decades, foresters managed forests under the assumption that all fires were inherently damaging to the landscape. “When we see a wildfire, our first response is to put it out,” in the words of the United States Forest Service. “For decades, the Forest Service has done just that when it came to wildland fires.”
Prior to the Euro-American settlement of Colorado’s Front Range, the region’s ponderosa pine forests burned often. Low-intensity wildfires swept across the landscape once every decade or so. These burns recycled nutrients, cleared the understory of woody debris, and groomed the woods of dead and flammable timber. But in the mid-1800s, Coloradan settlers started logging the state’s forests extensively. Vast swaths of America’s virgin forests were felled. And with time, “second-growth” forests grew in their place. All the while, the West’s new Euro-American settlers did their best to suppress wildfire. Forests were managed for economic growth, first and foremost; ecological health was an afterthought. Timber was money, and the bigger the trees, and the more of them, the better, as far as foresters of the time were concerned. As a result, Colorado’s forests have grown unnaturally dense.
A 2018 study published in Forest Ecology and Management analyzed how “forest structure” in Colorado has changed since the 1800s. Pre-settlement, Colorado’s Front Range ponderosa pine forests averaged about 97 trees per hectare (or 100 acres). Today, on that very same land, an average of 438 ponderosa pines grow per hectare of forest. Today’s Front Range forests, in other words, are nearly five times as dense as they once were, before these woods were groomed by human beings. Further up slope, Colorado’s high alpine forests are nearly twice as dense as the state’s pre-settlement woods. And these densely timbered forests provide surplus fuel for wildfires the likes of the Hayman Fire and Colorado’s record-breaking wildfires of 2020 to blaze at historic proportions.
Modern forest and fire ecology show that mild wildfires—on the scale of those to burn throughout history, in the absence of human intervention—actually bestow benefits upon the land. For millennia—since forests evolved, in fact—wildfires not only benefited forests, but functioned as an integral element in the health of the landscape. Lodgepole pines, for example, bear serotinous cones. They only regenerate in the wake of fire. The cones of these evergreens are coated in a waxy resin. When burned, this resin melts away, allowing the cones to unfurl and release their seeds, primed to germinate in freshly charred soil. On the most elemental level, wildfires were, and still are, needed for a healthy forest to thrive. In the words of the Colorado State Forest Service: “One of the overall benefits of wildland fire is that it is a catalyst for enhancing an ecosystem’s ability to sustain nutrient and water cycles and promote biological diversity. Wildland fires burning in their natural regimes reinitiate succession of vegetation communities. They foster new plant growth, which in turn, supports diverse wildlife habitats.” Wildfires also burn off debris accumulated in the understory of forests, reducing the chances of relatively mild fires jumping to the crowns of trees and fueling hazardous, sweltering blazes.
But Colorado’s forests haven’t been allowed to burn “in their natural regimes” for a century and a half. Since then, forests have grown denser, temperatures have risen, the climate has grown drier, droughts have grown more frequent and more severe, springs have come earlier and earlier to the mountains, and tremendous amounts of fuel load have accumulated in the understories of forests across the American West. Wildfire activity has intensified as a result. More severe fires have burned more land for longer periods of time over recent years and decades. In 1988, about 5 million acres of forest burned in wildland fires across the United States. In 2020, nearly 60,000 wildfires consumed 10 million acres of timber in flames.
This figure is projected to double once more by 2050.