Nearly every Western ecosystem needs fire. Flames thin overly-dense trees, disperse nutrients and stimulate new growth. But decades of logging, grazing and fire suppression have left many forests, especially in the dry Southwest, prone to fierce, high-severity burns that do more harm than good. In their aftermath are scorched, blackened moonscapes with powdery ash sifting through the air. Trees reduced to charred logs. Soil barbequed into a water-shedding crust.
Now, two new studies bear out the importance of lightening the fuel load in Western forests -- on a much bigger scale. The first, in the June issue of the peer-reviewed journal BioScience, was led by UC Berkeley scientists. It synthesized the results of 20 years of research on the effect of controlled burns and tree thinning on wildlife, vegetation, and soils, and found no permanent harm. And it encouraged much more of those activities.
“Today, the combination of wildfires and fuel-reducing treatments only touch 6-8 percent of the land that used to burn annually before 1800, and fuel-reducing treatments alone only affect 1 percent,” said lead author Scott Stephens, UC Berkeley associate professor of fire science. “That’s a pittance. At that level, it’s just triage rather than fire prevention.”
The need for landscape-scale fuels reduction is also underlined by a story in the Denver Post, describing how in Colorado, 10 years of lighting prescribed fires and mechanically thinning forests has not reduced the risk of high-severity wildfires.
About $29 million was spent in the state last year to thin and prescribed-burn nearly 50,000 acres, compared to $18 million and 33,000 acres in 2001. But that's still a tiny fraction of the overgrown forests that need treating, and the chance of catastrophic wildfire is greater than ever along the state's highly populated Front Range, which has seen years of drought.
"We haven't even begun to see the worst of the worst," said Ken Kerr, the Bureau of Land Management's senior officer in the federal command center west of Denver. "Until we start finding ways to treat more forests to avoid the catastrophic conflagrations, we're going to have problems. We can either pay now or we can pay much more later."
Using prescribed burns can be tricky, though – when they get out of control, as happened in March when high winds pushed one near Denver into a 4,000 acre blaze that killed three people, the public and political backlash makes forest managers understandably hesitatant to use them (even though less than one percent of prescribed burns escape control, according to the Forest Service).
Meanwhile, the trend, especially in the Southwest, is for fires that are much larger and more destructive than fires in the region historically were. A new study in Science Daily analyzed 1,500 years of tree-ring data and hundreds of years of fire-scar records:
The findings suggest that today's megafires, at least in the southwestern U.S., are atypical, according to study co-author and fire anthropologist Christopher I. Roos, Southern Methodist University, Dallas, and co-author Thomas W. Swetnam, the University of Arizona. Furthermore, the findings implicate as the cause not only modern climate change, but also human activity over the last century, the researchers said.
"The U.S. would not be experiencing massive large-canopy-killing crown fires today if human activities had not begun to suppress the low-severity surface fires that were so common more than a century ago," said Roos, an assistant professor in the SMU Department of Anthropology.
The scientists found that in ancient times, frequent small fires swept through forests, as well as occasional huge fires, but these fires weren't generally hot enough to travel into the crowns of trees and kill them. That kind of fire regime contrasts sharply to what's found today in southwestern Ponderosa forests, where wildfire occurs much less frequently, but tends to be severe and damaging.
And another new study, this one from Texas Tech University, predicts that climate change will create even more frequent fires in the West (for more about earlier studies of tree-ring records and what they revealed about climate change, see our story "Written in the Rings").
The study appears in Ecosphere, a journal of the Ecological Society of America. Researchers used 16 different climate models to project how global fire patterns might be altered by climate change. They found that by the century's end, most of North America and Europe could see more frequent wildfires, while tropical regions could see fewer.
"In the long run, we found what most fear - increasing fire activity across large parts of the planet," said lead author Max Moritz, a fire specialist in UC Cooperative Extension. "But the speed and extent to which some of these changes may happen is surprising. These abrupt changes in fire patterns not only affect people's livelihoods, but also they add stress to native plants and animals that are already struggling to adapt to habitat loss."
According to an email from Jose Iniguez, a Forest Service research ecologist in Flagstaff, Ariz.:
Now after the 2011 and 2012 fire season we have the results of these two strategies (letting fires burn versus putting them out). That is, after last year’s Miller fire and this year’s Whitewater-Baldy fire almost 400,000 acres have burned in the Gila, which is an area comparable to last year's Wallow fire in Arizona and NM (550,000+ acres). Given that these two areas had similar vegetation and experience the same climate patterns, one can assume that the only difference has been the “let burn” strategy in the Gila and the fire suppression strategy in the Wallow. Anyway, we are planning to compare burn severity between these two areas in the near future and it should provide a great perspective on the impacts of drought and climate change within two very different landscapes.
Watch for an HCN story on this research from Iniguez and others, sometime this fall.
And if you live in the Southwest, it's gonna be a long, hot, smoky summer.
Jodi Peterson is HCN's managing editor.
Image of prescribed burn courtesy Coconino National Forest.
Image of the Whitewater-Baldy fire courtesy Gila National Forest.