Our Future on Fire
A 6,000-year wildfire study shows climate change has created a dangerous new era for forests and humans
For the Aspen Times Weekly
Colorado’s 2020-wildfire season provided a glimpse at what climate change has wrought and it is an unsettling view.
The Cameron Peak and East Troublesome fires provided a devastating one-two punch to northern Colorado and became the two most destructive wildfires in the state’s history late last summer and fall.
On the West Slope, the Pine Gulch Fire north of Grand Junction was temporarily the state’s record-setter after burning more than 139,000 acres in August and September.
Closer to home, the Grizzly Creek Fire wasn’t on the scale of those blazes but presented extraordinary threats to infrastructure in Glenwood Canyon. Interstate 70 was shut down for two weeks. There were disruptions to railroad service and threats the city of Glenwood Springs water supply. The economy of the region took a hit at a time already made challenging by the COVID-19 pandemic. Now there are big questions for Glenwood Canyon in the fire’s aftermath (see related story).
Colorado’s forests were once regarded as more fireproof than those in the northern Rockies and California due to high elevations and generally wet conditions. But the 2002 drought and devastating fire conditions proved Colorado wasn’t invulnerable and foreshadowed conditions to come. The drought was one of the most severe in Colorado’s history. It helped the spread of the Hayman Creek Fire, which covered narly 138,000 acres and destroyed 133 residences. It was the state’s largest wildfire until 2020.
Closer to home, the Roaring Fork Valley suffered an eye-opening threat with the Lake Christine Fire in 2018.
Philip Higuera, an associate professor and wildfire researcher at the University of Montana, said 2020 is a sign that we must adapt.
“Years like 2020 will be more common,” he said. “That’s almost certain.
“Very broadly, it is clear with climate change over the last several decades and in particular in the 21st century, all forests throughout the West generally and in Colorado are becoming more flammable because of climate and because summers are becoming warming and drier,” Higuera said.
In a March 4 virtual presentation for the Wilderness Workshop-Aspen Center for Environmental Studies’ Naturalist Nights series and in a separate interview with The Aspen Times, Higuera discussed what he has learned as director of the PaleoEcology Lab and Fire Ecology Lab at the University of Montana. He has studied natural clues to wildfire activity over the last 6,000 years in the area that now encompasses Rocky Mountain National Park, so he is uniquely capable of putting current times into perspective.
“What I’ve been saying is 2020 kind of punctuates this trend we’ve been seeing over the last several decades,” Higuera said.
Those trends include a warmer and drier climate, increasing fire activity and growing prevalence of humans in fire-prone landscapes.
“Here’s the kicker for me and what’s been most surprising about 2020 — in some sense it seems like 2020 in combination with the rest of the 21st century is kicking these high elevation subalpine forests into territory they haven’t been in in recent millennia,” he said.
One way that Higuera and his colleagues study wildfire history is by collecting and examining sediment in high altitude lakes. Preserved pine needles help them determine the dominant species of trees during various eras. Ash layers help determine periods of wildfire.
There was a warm period from about 800 to 1,000 AD that accommodated high wildfire activity, though not as high as it has been recently. Averaging out the variability in the past, subalpine forests were experiencing wildfire about once every 200 years, according to Higuera.
That’s changing. We’re now in uncharted territory.
“Really to my surprise, what we’ve found is the 21st century is kicking this area outside of the historical range of variability,” he said. “This is the fire rotation period now — 112 years. Basically it means we’re burning at about twice the rate that these forests have experienced in the past. If we zoom into the last decade, it’s even more extreme.
“Rocky Mountain subalpine forests now appear to be burning more than any time in the past millennia,” he continued. “That is something that kind of had been predicted, but it’s happening earlier than we thought. The impacts of climate change are upon us sooner than we thought.”
Wildfires are also tending to be more destructive. Within a fire boundary, there is typically a mosaic of activity. There are some areas of intense fire severity, where vegetation is nearly all burned up, and areas of moderate and low severity. In general, Higuera said, there are now more fires with more intense burning. He noted with a degree of amazement that the East Troublesome Fire jumped the Continental Divide at 12,000 feet in Rocky Mountain National Park last year.
The history of fire suppression in the U.S. since the early 1900s hasn’t helped the situation.
The U.S. Forest Service followed a policy for decades of snuffing every wildfire. That stopped a process that benefited forests by encouraging regeneration and age diversity of trees. Fire suppression created a heavy buildup of fuels. Add drier conditions and more human presence, and it is a recipe for disaster.
Higuera said forest ecosystems have proven remarkably resilient in the past. Natural regeneration followed fires and led to healthy forests dominated by Engelmann spruce and subalpine fir trees.
Now, it’s uncertain forests will bounce back in a warmer, drier world. Forests might be thinner. Tree species might change. Aspen trees might be more dominant, assuming there is enough precipitation to allow them to flourish.
In some ways, Higuera said, the mold is set.
“Some of this increase in flammability, we’re going to be living with it for years or decades to come,” he said.
But he also sees these circumstances as an important call to action. He said the current conditions make him more worried for the human community than the non-human ecosystems. The ecosystems adapt.
“I think the more pressing challenge short-term is to figure out how we live in the high country — places like Grand Lake and Aspen and all these communities that are tucked into subalpine and lower elevation forests that are quite flammable,” Higuera said.
All told, about 7.4 million acres burned throughout the West in 2020. An estimated 10,000 structures were damaged or destroyed. Higuera said researchers have concluded that about one-half of that acreage would have burned naturally from causes such as lightning strikes. About one-half was due to human activity, from ignition and climate change.
Humanity needs to take climate change seriously and act on a global scale, he said. On the local level, people living in and adjacent to forests need to take wildfire protection planning seriously. That means incorporating rather than opposing fuel reduction projects.
“Recognize that a do-nothing option is not really a great, viable option for moving forward,” Higuera said. “That can make some people uncomfortable who really love forests and love trees and don’t want to see trees removed from forests in fuel reduction efforts.
“It kind of comes down to, if we want to live in these flammable landscapes, we need to accept that they’re going to be transformed,” Higuera continued. “They’re going to be transformed with or without us participating.”
Flames aren’t the only problem created by wildfires.
After a record-breaking wildfire season, Colorado now faces the aftermath in the burn scars. Mother Nature will determine the severity of events such as mudslides, debris flows and flash floods in 2021 and into coming years.
In Glenwood Canyon, the U.S. Forest Service and Colorado Department of Transportation are gauging the potential for problems such as the closure of Interstate 70 and popular recreational amenities such as the Glenwood Canyon bicycle path and Hanging Lake Trail.
The fire burned up steep slopes, charring the vegetation that anchored rocks and dirt in place. The canyon was already notorious for rockfall. Now the risk is magnified, according to Steve Hunter, a former engineer with the White River National Forest and a member of its Burned Area Emergency Response team.
The BAER team’s assessment showed that 12 percent of the terrain within the perimeter of the fire suffered a high level of burn severity, 43 percent was moderate, 33 percent was low and 12 percent was unburned.
The Forest Service started with emergency repairs to trails and roads last fall and will continue as weather allows this spring. Partner agencies are installing rain gauges to help with forecasts for flooding and debris flows.
Despite the precautions, an extended downpour could result in trouble for Interstate 70, the railroad line, the Glenwood Springs water supply and numerous recreational amenities.
The Grizzly Creek Fire topped out at 32,631 acres. The potential for problems is magnified by the Colorado mega-fires of 2020. The East Troublesome Fire covered 193,812 acres, originating north-northeast of Kremmling.
To the east of that fire, across the Continental Divide, the Cameron Peak Fire topped out at 208,913 acres, 25 miles east of Walden and 15 miles southwest of Red Feather Lakes.
The three largest wildfires in the history of Colorado occurred in 2020. They were:
Cameron Peak Fire208,913 acres
East Troublesome Fire193,812 acres
Pine Gulch Fire139,007 acres
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