The fire started in a place called the Savage Run Wilderness, a little slice of relatively unvisited lodgepole pine and spruce forest on the west side of the Snowy Range. A human likely caused the blaze.
It was a Thursday in late September. An unusually warm day during an unusually warm and dry month. A column of smoke formed and the blaze began to spread from fewer than 1,000 acres to nearly 20,000. By the next weekend, it jumped to almost 80,000 acres, prompting evacuations and closures over about one-third of the Snowy Range.
Friday afternoon, the Mullen Fire had jumped the North Platte River, crossed highways and roads, spotted new fires up to three miles away, and consumed nearly 130,000 acres. It has destroyed at least 29 homes and 31 outbuildings. More than 1,000 firefighters and multiple airplanes worked constantly to prevent the loss of more structures.
It’s one of the largest fires in Wyoming’s history. And according to local climate scientists, it’s another sign of the times.
“I find it hard to imagine a future where we move away from having a really high fire risk,” said Bryan Shuman, a University of Wyoming climate and geophysics professor. “The atmosphere keeps getting warmer and makes the fire season longer and means you have more dry air to make it possible to have big outbreaks of fires.”
One of the biggest contributors to the Mullen Fire has been trees killed by mountain pine and spruce beetles. The pests began working their way through the Snowy Range outside Laramie in the late 1990s. While both species are endemic to the area, they exploded in the last couple decades because of a lack of severe cold during winters that historically kept them in check, said Shuman.
What the beetles left in their wake was a sea of standing and fallen dead trees. The trees themselves were not a catalyst, Shuman said, but once the fire began, they helped fuel a fire that would become nearly impossible to contain.
“If you think about making a campfire, you don’t start with big logs,” he said. “Having a bunch of big dead trees around didn’t necessarily increase the fire risk, especially because they don’t have the fine branches and needles anymore, but once the fire gets going, you have lots of big logs and all these piles are like giant bonfires ready to go.”
And from there, the fire fed off of hot days, strong winds and little to no moisture in the atmosphere, said Bill Crapser, Wyoming’s state forester.
The fuels in the area have an incredibly high “energy release component,” which means how much of the fuel burns when it’s ignited.
Firefighters were hindered by a lack of access in heavily forested areas with thick downfall. Each time the fire dropped into a drainage, strong winds followed preventing any meaningful containment efforts, he said.
Then a week ago, wind gusts of 70 mph slammed the fire grounding any planes carrying water or suppressant and making ground attacks impossible.
“I don’t want to say it’s bad luck, but the fuels, weather and topography have lined up against us, the team and fire crews every time it’s made a run.”
Manage fire risk
Wyoming is no stranger to major wildfires. Nearly 800,000 acres burned in 1988 in Yellowstone National Park. In 2000, the Kate’s Basin Fire on the Wind River Reservation burned about 137,000 acres. About 1,300 fires burned more than 600,000 acres in 2012, including the Arapaho Fire in the Laramie Range that blackened nearly 100,000 acres and consumed about 90 buildings.
Many of the state’s lodge pole pine forests have to burn periodically—their cones only open with intense heat. But the Mullen Fire, now one of the largest in Wyoming history, is one more sign of what is possible in our warming, drying climate, said Shuman.
“Sure you will always have extreme events, but we’ve created the conditions for them to occur more frequently now,” Shuman said.
While lodgepole pine forests can burn as often as every 125 years, data shows that “most only burned about 9-11 times in the past 2,000 years,” he said. Even less frequently in high-elevation spruce-fir forests.
The Squirrel Creek Fire in the southern Snowy Range burned more than 10,000 acres in 2012, followed by the Beaver Creek Fire over the Colorado line in 2016. The Badger Creek Fire whipped through more than 20,000 acres in 2018. Roughly the bottom third of the Snowy Range will have burned in the last eight years.
While warmer, drier, longer summers are the root of the problem, variable storms are exacerbating it.
Late spring storms like what moved through in June dump heavy, wet snow and break trees already leafed out for summer, adding to the fuel load, Shuman said.
The early snow and cold snap in mid-September also contributed to the Mullen Fire, Crapser added. Snow broke limbs and the cold turned aspen and willow leaves brown and dry earlier in the fall. That meant instead of green leaves helping provide more of a natural fire barrier, they ultimately helped spread the flames.
Unfortunately, apart from slowing climate change, Shuman said there isn’t much humans can do to mitigate the continued extreme fire risk.
“The Mullen Fire burned right across wilderness, areas heavily managed, roads and the river. It doesn’t matter what you’ve done on the ground if you have this weather,” he said.
“The biggest thing that’s helping prevent the spread is where it’s burned before. Eventually we will stop having big fires because it will all have burned.”
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