How wildfires are shaping Montana winters.
BY GABRIELLE GASSER
On a cold, clear winter day, facets glitter atop a blanket of snow covering a hillside just south of Big Sky, Montana, in Yellowstone National Park. A group of backcountry skiers ascend a slope covered in blackened tree trunks, moving in and out of the shadows they cast. These charred skeletons are remnants of the 2018 Bacon Rind Fire that blazed through 5,200 acres. What the skiers don’t see as they climb uphill are the invisible processes that govern wildfire’s impact on winter as well as climate change’s command over this landscape.
Recent climate data published in the 2021 Greater Yellowstone Climate Assessment shows that temperatures are rising, wildfire season is expanding, and snowpack is retreating to higher elevations. These intertwined phenomena each help explain each other. Eric Larson, water supply specialist with the Natural Resources Conservation Service, explains their relatedness in an equation that goes something like this: The snowpack naturally absorbs and reflects solar radiation, also called shortwave radiation. The reflection created by the snowpack is an important process that helps to cool the planet. Summer burns leave an open slope peppered with charred trunks where there was once a sheltering canopy of trees. Without their shade, the equation is altered, and the snowpack absorbs much more radiation than it reflects. Snow starts to melt—faster and sooner.
These earlier melt outs, according to Larson, can then affect the duration of the season and the peak snow water equivalent or the amount of liquid water contained within the snowpack. He added that this in turn impacts water supply come
“Increased forest fires and the effects they’d have on our local watersheds is concerning, particularly because we might rely more on summer precipitation to sustain late summer streamflow,” Larson said. “That is not a situation I’d like to see, especially in a rapidly developing area where water supply demand is increasing.”
Impacts like these from wildfires are then amplified by climate change. According to Cathy Whitlock, regents professor emerita of earth sciences at Montana State University, the planet is projected to warm anywhere from 4 to 10 degrees by the end of the century, and so far Montana has warmed at a faster rate than the contiguous U.S.; National Oceanic and Atmospheric Administration data reveals that Montana warmed at a rate of .2 degrees Fahrenheit per decade between 1901-2022 while the rest of the lower 48 warmed at a rate of .16 degrees Fahrenheit during the same period. Whitlock says this seemingly small difference is significant, attributing it to Montana’s northern, land-locked location as well as the state’s high elevation.
Whitlock was a co-author on the 2021 Greater Yellowstone Climate Assessment, which projects that a trend of rising temperatures will likely cause more precipitation to fall as rain or a rain-snow mix, rather than snow, leading to less snowpack and drier summers. Additionally, warming is leading to more precipitation in the spring and fall rather than summer and winter.
“It’s not so much that you’re getting less precipitation, but it’s that you’re getting less of the precipitation as falling snow,” Whitlock said. The type of precipitation makes a difference.
“Our snowpack is considered our natural reservoir of water,” Whitlock said. “The longer we keep snow on the mountains then there’s more recharge of the soils, soil moisture, more water going into our streams … If you lose that natural reservoir and instead you replace it with something like rain, which doesn’t last as long, it evaporates from the soils more quickly, then your soils are going to be drier during the fire season.” She says moving into the future, fire seasons will trend longer and drier because of the loss of snowpack and increase in rain.
Each of these factors has a cyclical effect on the other. Warming and more fires means less snowpack which leads to less moisture which can then lead to worse fire seasons.
According to Custer Gallatin National Forest Fire Staff Officer Scott Schuster, the 2022-23 winter yielded a higher- than-average snowpack, but a warm May reversed a lot of those gains, melting the snow down to a near-normal level by June. But heavy summer rain was a saving grace, according to Schuster, and despite the early melting it was a quiet fire season. Last summer, 1,576 fires were recorded in Montana versus 2,630 total fires in 2021, according to the Montana Department of Natural Resources and Conservation.
Schuster, who has been fighting fire across the Western U.S. for 30 years, says when he first started, a 1,000-acre fire was considered large, and fire season was squelched by mid-September. Now, Schuster says the length of fire season is stretching on either end, and a June fire burning thousands of acres like the 2021 Robertson Draw Fire near Red Lodge, is considered commonplace.
This reality paints a picture of more of those charred, open slopes, promising changes to water supply, snowpack and even avalanche terrain. Bozeman-based Karl Birkeland has been working in the avalanche field for almost 45 years and currently serves as the senior avalanche scientist for the Forest Service National Avalanche Center. Though his focus is on snow, Birkeland said he is always interested in burn areas.
“If a fire wipes out trees in steep terrain, then [it] can form an avalanche path,” Birkeland said. “A place that might not have had avalanche danger before, now you have avalanche danger.”
Birkeland says another trend he’s observing in the backcountry is that snowfall is increasingly retreating to higher elevations, leading to less runoff for the following summer. Echoing Whitlock, Birkeland described the relationship between snow, fire and climate change as a “feedback loop.”
“When you start getting that snow line creeping up, the overall storage of snow ends up being less,” Birkeland said. “That means less snowmelt available for runoff during the next summer. That’s one of the things that we’re seeing a lot of over this last decade or two is … a huge amount of variability [in the amount of snow stored] in some parts of the country compared to what there was before.”
A strong El Niño weather pattern is expected to command the 2023-24 winter season, which can bring drier conditions, though Whitlock said the effect could go either way for southwestern Montana since it is in an intermediate transitional geography zone. Regardless of what this season brings, longer-term data suggests a trend of hotter and drier seasons. This will not only affect the snow sports that so many recreationists in Montana enjoy, but also the places they have chosen to live.
“One of the biggest worries about fire is the fact that we have so many people living in these fire prone forests now,” Whitlock said. “We’ve had large fires in the past, but now we have lots and lots of people living in places that are likely to burn.”
Gabrielle Gasser is a writer and photographer who grew up in Big Sky, Montana, and currently resides in Bozeman. When she’s not outside skiing or hiking, you can find her curled up with a good book.