The devastating fire seasons plaguing California’s Sierra Nevada may be a thing of the past after 2030, and that has scientists worried.
Their main concern? The area might not have enough trees left by the next decade.
A study published this past week in the journal Ecosphere suggests that dry mountain forests in California and other Western states will likely see ever-worsening fires for the next decade, followed by a period of fewer fires with less intensity.
Between now and then, wildfires turbocharged by climate change are expected to dramatically alter the landscape, leaving less fuel for blazes just 10 years from now, according to the study.
Researchers looked at the Big Creek watershed in the Sierra Nevada, near the source of a 2020 fire that burned 78,000 acres and destroyed much of a nearby town. Their goal was to get a better sense of whether the massive forest fires in recent years would become permanent in California. In order to do so, they had to build a simulation that could essentially predict what wildfires would look like years from now.
Their eventual model was adopted last week by the California Air and Resources Board to use in projecting the long-term impacts of fire on the California landscape.
What the researchers found in their study was that the Big Creek watershed near Fresno, if left alone, was going to pulse in a spasm of repeated fires over the next decade, by which point it would have blasted through enough of the large fuel on the landscape that — in combination with climate change — the land would no longer be hospitable to fire.
But without climate change, fires that recur at regular intervals would help “to constrain fuels” by sweeping the landscape clean of elements that otherwise allow big fires to build up and reach the canopy, said Maureen Kennedy, lead author of the study and an assistant professor at the University of Washington Tacoma.
The model found that climate change would speed up the decomposition of “little fuels” such as pine needles, fallen branches and leaf litter that drive fire by accelerating the work of the plants, animals and fungi that break them down. The end result would mean more trees burning.
Kennedy said climate change also drove drought, making the forest less productive. Over the long term, particularly beyond 2030, a decreasing amount of vegetation would mean less fuel and a decline in the frequency and intensity of forest fires.
Every forest and landscape tells its own story, Kennedy said, but there were certain broad conclusions that could be drawn from the research in California.
One such conclusion: The effects of climate change and decades of fire suppression efforts are linked. Climate change has caused the drought, higher heat and more volatile atmosphere that created the conditions for massive blazes. But fire suppression methods that left more fuel in place for the next blaze have also created problems.
“There’s a theory that if you remove fire, it homogenizes the landscape, and reduces variability, which gives you large patches of dead trees” that fuel firestorms, Kennedy said. “Whereas historically, you had a matrix of different landscapes” in a “more mixed” forest.
The simulation painted a bleak future for California’s dry forests. The next decade could see fires big enough that, in conjunction with climate change, they permanently change forest landscapes into brush and shrubs.
But the study also suggests a solution for policymakers, Kennedy said. In the dry forests, “the best way to deal with our fire problem is fire itself,” by following the example of the Indigenous peoples of California who intentionally burned millions of acres a year.
Today, Kennedy said, the best method is what’s known as mechanical fuel treatments — cutting down small trees and brush — followed by fire to clean out the tree debris.
“If we can conduct mechanical treatments and controlled burns, and create a patchy landscape, then even with climate change,” there’s a chance to save the forest, Kennedy said.