Anatomy of a Monster
How wildfires get that way
“YOU REALLY CAN’T STOP FIRE any more than you can stop a tornado,” says Don Latham, who leads the fire behavior unit at the U.S. Forest Service’s fire science lab in Missoula, Montana. But Latham and other researchers have for years mapped, modeled, and studied blazes in an effort to learn what makes them rage.
Fires come in three strengths, each phase an escalation of the last. Ground fires creep through the organic debris and decomposing litter in the soil, usually causing the least overall damage, while surface fires clear loose shrubbery and detritus from the forest floor. But dead wood and saplings serve as a ladder for surface fires to climb
into the canopy, where they become the blast furnace of wildfires: the crown fire, in which temperatures surge beyond 1,800 degrees Fahrenheit. The dead stuff goes first, and then when all the moisture is cooked out of the green wood, it goes too. Treetops can explode as the sudden intense heat ignites the gases inside them. Winds can carry
embers miles ahead of the advancing flames. Crown fires typically travel at one to five miles per hour, but a steep hillside and a strong wind can turn one into a 15-mph blaze, often belching out a downdraft that sounds like a freight train.
Some U.S. forests have adapted to devastating crown fires that sweep through once every 100 years or so. But much of what had burned across the nation at press time—mostly lower-elevation Western ponderosa pine forests—had not. In these ecosystems, historically adapted to surface fires, crown fires can become what Scott Stephens,
a fire science professor at the University of California at Berkeley, calls “stand-removal fires”—that is, fires that devastate, not replenish.Forest Service scientists have in recent decades developed computer programs that take into account such factors as terrain, wind, fuel, and elevation to plot a blaze’s expected course. But out on
the front lines, a raging crown fire is still difficult to predict. “When the fire gets going,” says Stephens, “you just get out of its way.”
Although it may take centuries for the land to return completely to its pre-fire state, parts of the forest start springing back to life right away. To hear federal Joint Fire Science Program manager Bob Clark tell it, the life cycle of a wildfire is a humbling thing to witness. “Fire doesn’t create things and fire doesn’t destroy things,” he
says. “It basically just rearranges.” —JOHN INGOLD
PRESCRIBED BURNS are not a panacea, though, particularly in Western states where human settlement has altered historical cycles of fire. “The areas available for prescribed fire are shrinking,” says Stephen Pyne, a professor of biology at Arizona State University who joined his first fire crew in 1967 and has since written nine books on wildfire. A century
of fire suppression, Pyne says, has so completely changed the rural ecosystem that natural fires quickly grow into disasters, as opposed to the smaller pre-settlement blazes that took out weak trees and grasses, leaving nutrients and a healthy forest. “Certainly in the West, the ponderosa pine areas were more like savannas than dense woods,” he adds.
Indeed, many of the areas we think of as beautiful, healthy forests today are actually unhealthy messes.
Chastened by the Cerro Grande fire, Secretary Babbitt has ordered up a slew of studies to deal with overgrown forestlands better than the current one-prescribed-burn-fits-all approach. According to Interior spokesman John Wright, Babbitt is particularly interested in a system that has come to be called the Flagstaff Model. Led by Wally Covington, a
professor of forestry and director of the Ecological Restoration Institute at Northern Arizona University, and funded by 17 public and private groups from both sides of the environmental fence, including the City of Flagstaff, the U.S. Fish and Wildlife Service, and Arizona Public Service (the state utility company), the Flagstaff Model is designed to
restore Western forests to a precolonization state.
“We have created an enormous change in this ecosystem from an open-grown and grass-dominated ecosystem to one dominated by trees,” says H. B. “Doc” Smith, program liaison for the institute and Covington’s right-hand man. “Before, there were perhaps 20 to 50 trees per acre. Now some stands grow to 2,000 or 3,000 trees per acre. It’s akin to taking off the
predators and watching the prey erupt.”
On a 500-acre test site inside Flagstaff city limits and a remote 3,500-acre site on Mount Trumbull, north of the Grand Canyon, the Ecological Restoration Institutehas cut out most of the trees, leaving the oldest and healthiest, and carefully burned away the underbrush. To offset the costs, they allowed lumber companies to do the thinning. What remains
is a more open stand that Smith says will eventually produce a carpet of grasses and wildflowers, such as lupines, asters, and geraniums. “What happens is, after the third or fourth year, the effects are softened,” says Smith. “You begin to see the wildflowers and less of the little chunks of charred material. People start to say, ‘By golly, this looks
But a proposal to implement the Flagstaff Model on a wider basis has angered environmentalists. “The problem with Wally Covington is he wants to cut everything back to 1900,” says Rex Wahl, executive director of Forest Guardians, a New Mexico&150;based group that has used the federal courts to stall a Forest Service plan to implement the model on
100,000 acres around Flagstaff. “There’s a major flaw in that. In 100 years, on average, there would be three to four established cohorts of trees, some old, some new. If you cut it back to 1900 you’ve denied all that production.”
Wahl isn’t alone in his criticism. Sandy Bahr, conservation outreach director for the Grand Canyon chapter of the Sierra Club, says Covington’s restoration is just another word for logging. “He’s taken an awful lot of big trees out,” Bahr says, referring to the Mount Trumbull test site. “It’s not like the forest got in this condition overnight, but I
think that, ‘Gee, we better cut those trees down before they burn,’ is taking things a little too far.” Even Paul Gleason sees the limits of the Flagstaff Model. “In limited areas next to houses, mechanical treatment is a viable option,” he says, referring to chainsaws and bulldozers. “But there is lots and lots and lots of ground where mechanical
treatments aren’t possible.”
To help appease their critics, Covington and Smith plan to test other forest management prescriptions alongside the Flagstaff Model. But the scientists are confident that their method will become one of many forest management strategies of choice in the West, particularly if it gets support from the Interior Department. “I think we have a chance if we
can get past the hypercritical environmental community,” says Smith, “and the notion that thinning is always bad.”