What scientists are learning from wildfire in New Mexico

  • An aerial view of a slope damaged by high-severity fire during the Whitewater-Baldy Complex incident.

    Michael Berman
  • The scene of a low-severity burn in a ponderosa pine forest in the Gila Wilderness.

    Michael Berman
  • Craig Allen, left, of the U.S. Geological Survey, consults a map with research ecologist José Iniguez while touring the Whitewater-Baldy Complex burn area.

    Michael Berman
 

New Mexico's Gila National Forest is an ideal place to study wildfire scars.  Ponderosa pines on the western cliffs have blackened bark at their bases. On the eastern range, frequent burns keep the grass treeless and nutrient-enriched, so that it stretches for miles like a thick green hide. From a small plane in July, I saw charred crowns swaying on the trunks of spruce and fir -- the aftermath of this summer's massive Whitewater-Baldy Fire.

The fire came after two winters of dismal snowfall left soils and vegetation extremely dry. Spring temperatures were nearly three degrees Fahrenheit above the 100-year average. In late May, lighting ignited a smoldering burn below Mogollon Baldy Peak. One week later, another fire started below Whitewater Baldy Mountain, just a short hike away. Strong winds merged the two fires, and the combined system took off like a flaming tornado. Two months later, after it was contained, 297,845 acres, 12 cabins and eight outbuildings had been burned.

Some saw this fire, the largest in New Mexico history, as a disaster. But for the scientists who convened in the Gila afterward, the Whitewater-Baldy Fire had created a perfect, landscape-scale laboratory. Over the past 40 years, wildfires in the remote reaches of the Gila have been allowed to burn more frequently than wildfires in many other national forests. This summer's wildfire gave researchers an unprecedented opportunity to observe whether more frequent use of fire can soften a blaze's impact and restore a forest to something closer to its evolutionary norm.

Research from the scientists' visit shows that large portions of the Whitewater-Baldy Fire burned less severely than other recent big fires in the Southwest, because it had less fuel powering it. It even helped portions of the forest better resist future serious fires by cleaning up undergrowth and killing smaller trees.

Larger forces, however, might yet undo decades of good work in the Gila. Scientists believe that climate change will make the Southwest hotter, drier, and more prone to pine beetle outbreaks and high-severity wildfires. Those forces might prevent burned forests from regenerating new trees.

"As time goes on, there will be a convergence of disturbances -- the adult tree seed sources are going to be dying because of beetle and drought stress and severe fires -- and then the question is whether (seedlings) can grow and survive," says Craig Allen, research ecologist for the U.S. Geological Survey.

The Gila Wilderness, which partially burned in the Whitewater-Baldy Fire, is the nation's oldest wilderness area, 558,000 acres in the middle of 3.3 million acres of national forest in southwest New Mexico. The small surrounding towns and sparse population enable forest officials to take more chances with fire.

Recognizing the necessity of fire to a healthy forest, Gila fire managers wrote one of the nation's first forest-wide fire plans in the 1970s. It allowed small wildfires to be managed for ecosystem benefits instead of being immediately stamped out. Over the next three decades, firefighters grew comfortable manipulating fire over every local district and forest type. Of that burn-savvy culture, Gabe Holguin, Gila staff fire officer, says, "It came down through the ranks. It's just a passion you have for the wilderness, and it kind of drives you to want to do the right thing."

To be sure, the Gila, like other forests, faces pressure to stamp out wildfires. Its managers followed this summer's directive from Washington, D.C., to suppress all fire starts, in hopes of keeping small fires from becoming big, expensive ones. On average, the Gila's progressive fire management suppresses 98 percent of lightning-caused fires, while the nation as a whole suppresses 99 percent. Still, that 1 percent helps Gila managers burn an average of 100,000 acres a year, plus an additional 20,000 acres from an aggressive prescription-burn program.

Out in the woods, José "Pepe" Iniguez, a Forest Service research ecologist, led me up a steep incline above Gilita Creek. We found an open ponderosa forest at the top. With other federal scientists, we hiked down into the low country, which showed little sign that the fire had even occurred. In just over a month, the grass had grown thick. The ponderosa trunks were blackened but not severely charred.

Cicadas sounded like bug zappers around us. "Could you have taken us to anything more park-like, Pepe?" Craig Allen quipped. It did indeed feel like a park, with big, widely spaced trees unhindered by brush and deadfalls. This puzzle of fire scars was an easy one to solve: Southwestern ponderosas are adapted to frequent, low-severity fires that clean up the understory. The area had burned two or three times in the last 40 years.

Preliminary conclusions suggest that the vast majority -- 87 percent -- of the Whitewater-Baldy Fire burned at low and moderate temperatures, mostly in ponderosa and mixed conifer forests, killing individual trees or small pockets without incinerating entire stands. Eighty percent of Whitewater-Baldy's total spread had burned at least once in the last century, and while solid numbers aren't yet available, researchers think that little of the forest's ponderosa pine burned at high severity. Another recent Gila fire, last year's 88,000-acre Miller Fire, burned almost exclusively in ponderosa pine forests, and only 143 acres  burned at high severity. In comparison, only 40 percent of the ground covered by last year's 538,000-acre Wallow Fire in Arizona had burned in the last 100 years; about 27,000 acres of ponderosa pine burned at high severity.