Rocky Mountain high-elevation forests burned more in 2020 than they have in 2,000 years, according to researchers from the University of Montana and the University of Wyoming.
UM professor Philip Higuera said he and his team conducted the study of present and historic burn patterns using data collected during 15 years, reports the Daily Montanan. He said that this research is important because it highlights the effects of climate change on the severity of fire seasons.
He said that high-elevation forests are a good indicator of climate change because due to their burn-free periods, they have been less affected by burn mitigations the way lower-elevation forests have.
“We write that these forests are good sentinels of climate change for kind of two reasons,” Higuera said. “First, because they’re high elevation, they’re cooler and wetter compared to low elevation forests. With fire-free periods of one to two centuries, these forests have typically had a lot of dead fuel, twigs, dead trees and stuff on the forest floor, and you’ll see that today. That’s not a consequence of fire suppression; it’s not unusual relative to the past. A hundred years, or 50 years of fire suppression in these forests that typically burn once every one to two centuries has a lot less of an impact compared to fire suppression in low elevation forests that may have burned once every several years or several decades historically.
“Given that history, it’s hard to invoke past management or fire suppression as the cause for this increase.”
Higuera and his team studied sediment core samples from 20 lakes in their study region, giving the team a wide range of data to examine. He said the team slices the core samples into small sections and analyzes the charcoal content, which shows spikes and dips in the number of fires in a season.
“Collecting the cores is kind of like, you know, sticking a straw into the mud, putting your thumb over it to create a seal, and then pulling it up,” Higuera said. “As we go down into the mud, we’re going back in time.”
Higuera said that analysis of the cores shows that 2020 was the worst fire season in the Rocky Mountain high-elevation forests in more than 2,000 years, and rising global temperatures are partly to blame.
“From a personal perspective, it was kind of shocking to see 2020 unfold. Maybe it’s happening a little bit earlier than we thought, but this isn’t outside of what co-authors and I, and other scientists, have been predicting,” Higuera said. “What is clear, when we compare both past variations in fire activity prior to 1900, well before the Forest Service and Euro-American land management, even in the past, we see fire activity track smaller scale variations in climate than what we’re experiencing now.”
He said that the climate is becoming warmer and drier, affecting high-elevation forests, drying them out and making them easier to burn.
“That’s making the dead vegetation, which is a common part of these forests, it’s making it drier, and in some cases drier than it has ever been in the observational record, like in 2020,” Higuera said. “That really dry fuel is what enables large fires to occur. So it’s not the only cause, but it’s kind of the overarching thing that’s making these high-elevation forests dry and able to burn.”
Higuera said that we had been predicting the kind of huge fire loss seasons like the one in 2020, but what happens after that is uncharted.
“For probably several decades, summers continue to be warmer, drier, and longer. A lot of it will depend on the extent to which we, and the global community, addresses anthropogenic (human-caused) climate change,” Higuera said.
Rocky Mountain areas should expect fire seasons to remain bad in coming years, he said.
“These communities across the Rocky Mountains are going to increasingly be facing these large fire events and conditions that are unlike what we’re used to over the past several decades, but even conditions that differ from what these ecosystems have existed with for thousands of years,” Higuera said.
Higuera said that data from the core samples indicates that the 2020 fire season broke a record previously held by an unusually warm period in the Middle Ages.
Kyra Wolf, who worked with Higuera on this research, said she knew things were bad when the fires were still strong late in the season.
“It was surprising to me for a few reasons, partly because there were fires that started late in the season that became very large, in September and October, which is usually when things start winding down as temperatures drop and precipitation picks up,” Wolf said. “So that was surprising to me and seeing fires jump over the continental divide, which typically doesn’t have a lot of fuel and doesn’t usually burn, was really surprising. That acts as a pretty good fuel break in most situations.”
Wolf reiterated Higuera’s point that these fires will be more normal as temperatures continue to rise and that addressing climate change is the best course of action to mitigate future fires.
“I think this is going to be what we consider a new normal in the West… a lot more fire, at least in the next few decades, and that really highlights the need to act on climate change,” Wolf said.
Kimberly Davis, a research scientist at the University of Montana, said that scientists are working on new methods of mitigating climate change, a key factor that causes extreme fire seasons.
“There’s been a couple of studies that have come out recently that suggest that in addition to reducing emissions, we also need to start to take some carbon out of the atmosphere as well,” Davis said.
She said that there are different solutions scientists at the Nature Conservancy are looking at, including carbon capture technology and land management.
“For example, in the U.S., their analysis suggested that there’s a bunch of land that could be reforested, that used to be forest, and that’s not currently forested,” Davis said. “Planting trees and having those trees take up carbon could help reduce the carbon in the atmosphere.”
Davis said that research from Joe Fargione of the Nature Conservancy suggests that removing carbon from the atmosphere has the potential to significantly impact climate change.
“They did a whole carbon analysis and they found a maximum potential which is the equivalent of about 21% of our current net annual emissions in the U.S. So if we did all of these things that they said and they all worked out how they expect, that would take up about 21% of our annual emissions in the U. S. So, that’s significant, but we still need to really focus on reducing emissions,” Davis said.