Following a devastating wildfire season in 2020, new research shows that high-elevation forests in the Rocky Mountains are burning more now than any time in the past 2,000 years amid extreme, climate change-induced drought.
The study, published Monday in the Proceedings of the National Academy of Sciences, concluded that fire activity in subalpine forests of northern Colorado and southern Wyoming is unprecedented in the last several millennia — a clear signal that the climate crisis is increasing the severity and extent of wildfires in the West.
Rising temperatures and prolonged drought in the West will continue to exacerbate and accelerate wildfire activity for at least several decades, scientists say. Philip Higuera, lead author of the study and fire ecology professor at the University of Montana, told CNN last year’s wildfire season was a game changer.
“After 2020, it’s clear we’re in uncharted territory,” Higuera said. “People are being negatively impacted by these wildfires either directly or indirectly. Climate models suggest that this trend is only set to continue.”
The current drought sets the stage for another brutal fire season in 2021, particularly in California where rainfall deficits and dead vegetation are already breaking records that scientists didn’t expect until August, Higuera said.
The 2020 wildfire season pushed Higuera and his colleagues to analyze historical fire records to understand how 21st century activity differs from the past. In addition to historical records, they also used charcoal found in lake sediments around the subalpine forests — or high-elevation forests — to compare how often fires have occurred in the area on average in the last two millennia.
Higuera’s team found that last year’s wildfires accounted for 72 percent of the total charred area in the subalpine forests since 1984. They also found the current rate of burning is 22 percent higher than the maximum average rate over the past 2,000 years — a period of time the temperature in the Northern Hemisphere was actually slightly higher than it was during the 20th century.
The study’s authors say the increase is a particularly significant climate impact, since subalpine forests typically burn less frequently than lower elevation forests.
Higuera called the results “sobering.”
“Understanding how ecosystems have changed in the past is one of our best ways to learn more about how our forests change as climate changes,” Higuera said. “Studying the past is so important because it really helps highlight the degree to which we are changing the landscapes that we live in now.”
Jennifer Marlon, a climate scientist at the Yale School of the Environment who was not involved with the study, said these results suggest the seasons are shifting.
“When you get extreme heat and drought together, that’s a recipe for really severe wildfires,” Marlon told CNN. “The fingerprints of global warming are all over this kind of fire behavior.”
Concerningly, Higuera said, what has worked to prevent wildfires at low elevations — controlled burns — is not an easy solution for subalpine forests.
“In lower elevation forests, it’s an easier proposition to say we need to return prescribed fire to these forests to help get them back to conditions similar to how they were before fire suppression,” Higuera said. “It’s not as feasible in high elevation forests.”
“Fire managers are faced with challenging decisions,” he added, “whether having to modify the way that fire exists in these systems versus accepting these high severity fires, which is hard when they burn close to human communities.”
Forests are vital to addressing the most dire effects of the climate crisis. They not only protect biodiversity, but also absorb and store carbon dioxide emitted from human activities. But as wildfires worsen, the carbon stored in these forests is increasingly released back into the atmosphere, an impact compounded by bad air quality.
Scientists say that forest ecosystems including the subalpine in the Rocky Mountains could soon reach a tipping point unless climate change is addressed. But Higuera warns that the solution isn’t to eliminate fire from management systems because it has historically been part of the life cycle of forests.
“One of the challenges of living in the West is that we know that fire is an important component on these landscapes,” he said. “If we remove it, that will take away a lot of the things we’ve come to expect such as species composition. The challenge for us is to be able to learn how to live with fire on the landscapes in ways that do not turn into human disasters.”