To those who live in wildfire-prone areas, the prospect of wildfires, though certainly not welcome, are expected. An odd canter emerges from an otherwise seasonally pleasant rhythm. Yet it now appears destabilized. What semblance of security snow cover once provided evaporated this past weekend as Colorado's second major fire threatened roughly 8,000 residential buildings. And perhaps most shockingly, the wildfire roared through a snowy landscape.
Beneath the iconic slabs of red sandstone — sentinels marking the boundary of the Great Plains — known as the Flatirons, the NCAR Fire ignited last Saturday in Boulder. Skirting the southern edge of the city, the wildfire tore through 190 acres of still-dormant grass on the snow-speckled foothills of the Rocky Mountains. Unusually warm weather leading into the weekend led to a great deal of moisture in the soil from snow melt. Where there was no snow cover, flames prevailed.
A 27-year veteran of wildfire management in Colorado, Boulder Wildland Division Chief Brian Oliver told reporters "anytime there's not snow, there's fire."
"Fire season's year-round now," Oliver continued. "There's really no season. If there's not active precipitation or snow on the ground, as you can see, it's March, there's no fire season, per se, and we just had a 200-acre fire."
Acting as an incident command trainee, Oliver managed containment efforts with several other commanders.
There is no hard and fast rule dictating that fires occur strictly in the four-month period from June to September known as "fire season." However, wildfire danger levels have historically been quite low outside of that period. A culmination of risk factors — an ignition source and readily available dry fuel — rarely align.
Though fires are not unheard of in March, they have by no means been the norm. That may not be the case as climate change continues to accelerate drought and alter regional atmospheric conditions. As Boulder County now experiences warmer winters, less snow-pack, and earlier spring runoff, according to the University of Colorado, Boulder, the fire season there is likely to double.
Oliver's statement represents a broader shift as federal agencies, including the United States Department of Agriculture, officially recognize that wildfire prone areas have succumbed to longer periods in which fire is prevalent. Experts at NOAA analyzing meteorological records found that, on average, Colorado got 2º F hotter over the last 30 years. Within that time period, the 10 largest fires in recorded history of the state occurred after 2002.
That is, the Marshall Fire fits into a relatively recent trend of large wildfires outside of the typical fire season as does the still-smoldering NCAR Fire. In fact, they were not alone. Several smaller blazes ignited further north in the last few days, according to data the Fire, Weather & Avalanche Center compiles continuously. Thousands of acres burn across Texas and Florida.
"More and larger co-occurring fires are already altering vegetation composition and structure, snowpack, and water supply to our communities," Iglesias explained.
"For many USDA Forest Service employees, fire season is something they remember from the start of their careers, when they quickly learned there were five seasons: winter, spring, summer, fall and fire season," reads a statement on their website. "However, wildfire is year-round for much of the United States and the Forest Service is shifting to the concept of a fire year."
The prevalence of wildfires in Boulder is a bellwether indicative of a shift toward year-round wildfires. Dr. Janice Coen, an expert in wildland fire modeling, emphasized, however, that examining a single wildfire, a single fire season or even a decades-long trend, however, as an example of the human impact on climate conflates correlation with cause. Foresters and fire ecologists, experts from whom wildfire management specialists like Oliver draw information about wildfires, employ methods of observation and trend forecasting Coen described as speculative.
Coincidentally, Coen is a research scientist at National Center for Atmospheric Research's (NCAR), for which the NCAR Fire was named as a result of the proximity of one of its labs to the burn area.
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"If we are in one of these periods where the snow cover is covering the ground for less of the year, that's increasing that component and it increases the probability that a large rapidly growing fire can take place," she added.
Still reeling from the astonishingly rapid spread of Marshall Fire, city officials issued evacuation orders that displaced over 19,000 people, including employees at the NCAR Mesa Lab. At a media briefing on the scene, Oliver reported minimal losses and zero fatalities as of Monday. The NCAR Fire stopped forward progress within 100 yards of residential properties.
Halted spread and the prospect of rain prompted authorities to optimistically lift evacuation orders.
Just three months ago, communities nearby in Louisville, Superior, and surrounding areas were not so lucky. Only debris and foundations remained of over 1,000 homes. Officials presume two individuals still missing are deceased. In the aftermath, charred human remains were found in the rubble. Still more buildings were damaged, and police perimeters continue to guard neighborhoods from looting.
Calling it a "big community win" Oliver applauded the interagency operation at the NCAR fire. It could have been much worse. With an estimated $1 billion in insurance claims alone, in terms of property loss, the Marshall Fire that overshadowed the first days of 2022 dwarfs the NCAR Fire as Colorado's most destructive fire on record.
Since the Dec. 31 Marshall Fire, almost 15,000 fires and over 500,000 acres have been burned across the nation. Parsing out the exact reason why remains more difficult. While it is clear that humans have created conditions ripe for larger wildfires, not all scientists agree about the relative influence of human-driven fuel loading and droughts on the actual wildfires.
Coen added that drought is not even a necessary precondition for these grass fires like NCAR and Marshall. What is significant is not the moisture in the soil. Oliver added that grass is still dormant until later in the spring, so it doesn't take up any of the moisture from the soil. Without snow cover, it can dry out rapidly. With the Marshall Fire, the alignment of factors aligned horrifically.
"The winds were blowing strongly, so the grass dried quickly, and we had a fortuitous ignition," she said. "When you have this underlying susceptibility — in this case the grasses could come into that condition very quickly on top of which there's a weather event, which last one to five days, typically, and on top of that, you have a fortuitous ignition. So it's when three things happen at the same time, rather than necessarily things getting drier and drier and drier."
Comparatively, the Marshall Fire dwarfed the NCAR Fire, tearing through over 6,000 acres of residential areas in Boulder County. Wind gusts topping out at over 100-mph whipped up fire whirls — tornado-like columns of flame — that leapt across neighborhoods. Firefighting efforts were not enough to stop the flames then, but wind was on the side of firefighters this time. Coen indicated that the prevalence of such strong winds coming down from the mountains is becoming increasingly common in Colorado.
The frequency of these weather episodes of one to five days that can simultaneously dry grasses and spread large fires open the tinder box so to speak, but the match is an increasing encroachment of development into these fire prone areas. Lightning rarely overlaps with dry spells. A vast majority of fires are actually started by people directly.
"Development introduces ignitions (e.g., cigarette butts, powerlines) and flammable material to fire-prone areas, thus increasing the probability of fire itself."
"Many of the homes burned in Superior, CO definitely weren't there when I moved here almost 30 years ago — and our electricity structures and our cars and everything else we bring with us," Coen described.
From 1945 to 2015, according to Dr. Virginia Iglesias, a researcher at the University of Colorado, Boulder's Earth Lab, human encroachment on fire prone areas was 10 times higher than it was nationally and densification of already developed land was three times higher.
"The consequences of these trends are twofold," Iglesias explained. "First, accelerated development in hazardous areas implies that the number of homes that could be affected by fires is increasing rapidly. Second, development introduces ignitions (eg, cigarette butts, powerlines) and flammable material to fire-prone areas, thus increasing the probability of fire itself."
"Decades of fire suppression in several regions have resulted in fuel build-up conducive to more intense fires," Iglesias said. "In the West, aridification has doubled the extent of fire prone ecosystems. Up to two thirds of this increase in aridity have been attributed to anthropogenic warming."
In a March 16 paper published in Nature, Iglesias and other scientists found that fires in the United States have quadrupled in size while tripling in frequency and range in the last two decades. Their analysis showed that changes in climate, fuel and ignitions projected for arid regions of the continental United States — the West, Southwest, and Great Plains — are already underway.
"We documented a shift to more and larger fires, and found that fires today affect areas that didn't burn in the past," asserted Inglesias. "Concurrent ignition, fuel, and low moisture are prerequisites for burning. Other studies have shown that, although natural variability possibly played a role in altering fire patterns, anthropogenic impact largely explains the changes in fire."
According to Coen, large fires tend to occur when there is an underlying susceptibility, but drought is not the only factor. There are several components: Was it a day when the fuels were dry enough? Was there weather to spread the fire? Did we have an ignition at the location to take advantage of that?
"If the seasons are extending when the ground is susceptible, that increases our fire risk. If there are more people bringing ignitions, that increases our risk. It's just that it's not just one of them. We have to look at them together."
These are constantly shifting and so much complexity underlies various natural cycles determining wildfire prevalence as Coen highlighted, but what matters is that the trend is there. A need for adaptation to these wildfires is clear.
"More and larger co-occurring fires are already altering vegetation composition and structure, snowpack, and water supply to our communities," Iglesias explained. "This trend is challenging fire-suppression efforts and threatening the lives, health, and homes of millions of Americans."
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