Megafire

by Michael Kodas

  The Fish and Wildlife Service canceled the burn.

  Lucas welcomed Rocky Flats’ next-door neighbors as a population that actually cares about the refuge, but noted that some of their homes are within the reach of wind-driven flames from the prairie fires that become more likely each year the grassland doesn’t burn. Grazing or mowing the grass could reduce the hazard but won’t save the tallgrass, or the species dependent on it.

  The USFWS still hopes to hold controlled fires at Rocky Flats. One way or another, Lucas said, the grassland is certain to burn.

  15

  The Vanishing Forest

  WHILE RADIOACTIVE FALLOUT AROUND CHERNOBYL led to a thickening of the forest, the woodlands around Los Alamos were getting “nuked” by wildfires.

  Valles Caldera was named a national preserve in 2000, the year the Cerro Grande Fire burned hundreds of homes in the nuclear city just east of it. Eleven years later winds blew an aspen onto a power line at the edge of the caldera. In its first 14 hours the Las Conchas Fire burned 43,000 acres—as much as the Cerro Grande burned in two weeks. In total the 2011 fire destroyed 63 homes and 49 outbuildings, and grew to 156,593 acres—almost three times the size of its predecessor.1

  At its peak it burned nearly an acre a second.2 Its fastest rates of spread were downhill and against the wind—behaviors never seen before by the firefighters in front of it. It created its own weather and sent another massive plume of smoke into the sky over Los Alamos.3 This time officials wasted little time evacuating both the lab and the city.

  “I think it’s been 8,000 years since we’ve seen a fire of this severity,” Craig Allen told me when I visited Valles Caldera after the fire.

  “The really ugly stuff goes on for 10 miles that way with barely a tree standing,” he said, pointing to the southeast. “There’s a 30,000-acre hole in what used to be forest and woodland, centered on that first day’s run.”

  Allen, a research ecologist with the U.S. Geological Survey, was in his 30th year working in the Jemez Mountains when I visited. He pointed out a six-square-mile area where the blaze killed almost every tree.

  The term “moonscape,” like “megafire,” is bandied about by some in the fire community and disdained by others, but in the case of the Las Conchas Fire, it was hard to think of a more accurate description. At the heart of the wasteland, the forest was “nuked”—another firefighter’s term that’s eschewed by science but fitting for both the scene and the atomic laboratory down the road. A charred stubble of stumps spread for miles on ground burnt bare and brown. The lone black skeleton of a 30-foot alligator juniper stood in the middle. Thousands of incinerated ponderosas looked like brushstrokes of black ink against the gray ash. Other pines were dead but not charred. The fire was so hot that it killed them without touching them.

  Heat had killed more than 90 percent of the preserve’s piñon pines before the fire even started. Tree rings show that the dry spell after the turn of the millennium was less severe than others the piñons survived in the past, but temperatures ran a couple of degrees hotter. Studies by Dave Breshears, an arid lands ecologist at the University of Arizona, and Nate McDowell, a tree physiologist at the Los Alamos Lab, showed that the increased heat magnified the impact of the drought, making the trees more vulnerable to insect infestations. The bugs ultimately killed them, but the piñons could have spit them out if the temperatures hadn’t weakened them or the drought hadn’t deprived them of the moisture they need to defend themselves with sap.4

  McDowell tested how much heat and dryness the trees can endure by enclosing piñons and junipers in acrylic cylinders (which look like giant test tubes from a science fiction movie) in which he can control the temperature and moisture. The trees around Los Alamos, his experiments showed, are at a climatic tipping point. They can tolerate little more drought and heat, and those aren’t the only limits they are pushing up against.

  Craig Allen and Bob Parmenter, the science and education director for the Valles Caldera National Preserve, led me to a slope that looked down over the extinct volcano. Grassy meadows filled the bottom of the crater, while ponderosa pines, junipers, and a few surviving piñons covered its slopes. “Grasses dominate the caldera,” Allen said. “With a reverse tree line.”

  The forest is plagued both by the death of some trees—the piñons—and an overabundance of others.

  Historically, the woods took to the colder, moister soils above the meadows. Grasses and the ground fires they fueled kept the trees out until grazing livestock arrived. More than 100,000 sheep dined on the caldera’s grasses early in the twentieth century, followed by as many as 12,000 cattle after World War II. As the livestock grazed down the grasses, the pines moved in. Using aerial photos, Parmenter determined that the area of open grassland declined by 55 percent between 1935 and 1979.

  Decades of grazing and fire suppression left some of the forests in the caldera with an exponentially greater density of ponderosa pines and understory growth. The excessive fuel turned mellow ground fires into explosive crown fires, and the thirsty vegetation magnified the water shortage in the already arid woodlands.

  The preserve has since reduced the livestock in the caldera by 95 percent, but it takes a long time to fix a forest. And there’s no way to mitigate the increasing temperatures and drought plaguing Los Alamos.

  Thirst and bugs can wipe out a forest, but they don’t kill every tree. Young trees that survive will eventually recolonize the landscape.

  But megafires are different. “When you have a high-severity crown fire burn through a piñon stand or ponderosa stand over a huge area, it takes out all the seed source,” Allen told me. “That’s why these . . . big, high-severity fire patches are a big deal. We’re not getting forests back.”

  While even Allen would admit that good-sized patches of severely burned forests are an important part of many forest fire mosaics, in some fires those areas are so large that they remain treeless. Trees that release their seeds in wildfires to resurrect a forest—called obligate seeders—are vulnerable to an increased frequency of fires. Blazes that recur more often than a forest has adapted to can kill the young trees regenerating from the previous blaze before they’re old enough to drop their own seeds, thus wiping out the species in that location unless the area is small enough that unburnt trees nearby can spread seeds to the burnt area. In some cases a new forest of trees better suited to the increased fire frequency will grow, but in many regions shrubs, weeds, or grasses replace the trees. Research published in 2013 by David Bowman at the University of Tasmania, in Australia, shows that abrupt changes in the frequency or intensity of fires, like those around Los Alamos, can bring landscape-wide loss of obligate seeder forests.5

  “If you don’t have any mother trees surviving in the midst of these big patches, you don’t get tree regeneration,” Allen said. “You have a lot of time for shrubs and grasses to take over . . . which then makes it more difficult for trees’ seedlings to establish, even if there were seeds.”

  In multiple lines of evidence over thousands of years, Allen sees human impacts having something of a slingshot effect on the fires and forests in the Jemez Mountains. For at least 6,000 years frequent low-intensity ground fires shaped the landscape—keeping forests thinned and preventing timber from overtaking grasslands. But with the arrival of railroads, grazing livestock, and, finally, the nuclear laboratory and the town that served it, humans snuffed that fire cycle. The forests grew thick and sick.

  The Cerro Grande Fire that burned into Los Alamos marked the snapping of the rubber band. During the subsequent 15 years a cycle of intense drought and record heat fell onto the overgrown forests. Crown fires in New Mexico and Arizona burned bigger now than in hundreds of years6 and proved nearly impossible to stop. “At the Cerro Grande, the fire model shows that if we hadn’t fought it at all, it would have gone exactly the same way,” Allen said.

  During a severe drought that struck the area in the 1950s, the largest fire in the southwestern United States wa
s about 50,000 acres, according to Tom Swetnam at the University of Arizona’s Laboratory of Tree-Ring Research. Today the Southwest is seeing fires nearly 10 times that size. In Arizona the Rodeo-Chediski Fire burned 468,000 acres in 2002, and the Wallow Fire burned 469,000 acres just nine years later. It’s a phenomenon so well documented in the region that it has come to be called the Southwest Ponderosa Pine Model.

  Swetnam and fire anthropologist Christopher I. Roos looked at nearly 1,500 years of fire scars and tree rings to create a statistical analysis showing that during both the warm centuries and the cool ones, ground fires behaved largely the same until this century. Recent megafires in the Southwest, their research suggests, would not be occurring if humans hadn’t removed ground fires, added grazing animals, and otherwise impacted the landscape.7

  The forests survived deeper droughts in the past. But the combination of drought, increasing temperatures, overgrown woods, and overgrazed grasslands drives fires that overwhelm their resilience. The size of patches where nearly every tree is killed—like that 30,000 acres in the Las Conchas Fire—leaves mother trees too far away to provide the seeds that would regenerate the forest.

  The impacts trickle down to plant, animal, and human communities. After the Las Conchas Fire, the cities of Albuquerque and Santa Fe had to close their water intakes on the Rio Grande for some 40 days due to contamination and gunk from the fire. That has led those cities and organizations like the Nature Conservancy to radically scale up the amount of prescribed burning and thinning in the woodland watersheds.8

  The threats to the forests of the Southwest are increasing rapidly. In the fall of 2012 researcher A. Park Williams and colleagues created the “forest drought-stress index” using more than 1,000 years of tree-ring data from ponderosa pines, piñons, and Douglas firs—the dominant conifers in the Southwest.9

  The current drought is “the worst . . . in the last thousand years,” Craig Allen, one of Williams’s collaborators, told me. And Williams’s index shows that if climate models are correct, the droughts of the coming century will continue to exceed any in the past millennium, dealing even more punishment to trees. In his 2013 paper he describes how “vapor-pressure deficit” stresses them. The atmosphere around the trees is so dry and hot that the stomas—the tubes that move water through trees—close to keep the plant from drying out completely. But the trees, which also get their nutrients through the stomas, will starve if the tubes remain closed for long. And if the hot, dry air draws moisture from the trees faster than their circulatory systems can move it, the stomas can collapse under the stress like straws sucking ice cream.

  By 2050, Williams contends, conditions will be beyond what most coniferous forests in the region can survive.

  “Even without climate change, [which is] expected to drive further stress to forests and to change tree species and to change where they are on the landscape . . . we’re talking centuries without trees,” Allen said. “That 30,000-acre hole, most of that will still be treeless several centuries from now . . . tens of thousands of acres of Las Conchas that won’t be back as forests for centuries.”

  The decline of those forests, Allen noted, may be a harbinger of widespread forest changes around the planet.

  Through heat, thirst, and the twin plagues of insects and wildfire, the warming climate is driving forest die-offs on every wooded continent. In California, Forest Service researchers in 2016 documented 102 million trees killed by drought and insects across the state since 2010, 62 million of which died just that year.10 The Carnegie Institution for Science identified tens of millions more that were suffering severe enough drought stress that they were at risk of dying.11

  Already many forests that were once carbon sinks are releasing more CO2 than they suck from the atmosphere as they fill with unhealthy, old, or unnaturally fire-prone trees. Woods that once cooled the earth are beginning to warm it, putting the forests around Los Alamos in the middle of a vicious cycle of climate and fire.12

  LATE IN THE SPRING OF 2012 I climbed a peak above Boulder hoping to find blue sky, but the air was filled with enough smoke to make me cough. The Whitewater-Baldy Fire burning in the Gila Wilderness of New Mexico, more than 600 miles away, had grown into the largest fire in the state’s history—surpassing the record set by the Las Conchas Fire just the year before. It was hard to see hope in the haze, but it was there when I looked for it.

  Jose “Pepe” Iniguez, a research ecologist with the U.S. Forest Service’s Rocky Mountain Research Station, was eager to get into the Gila Wilderness (part of the Gila National Forest) after it burned. He had plots set up to compare how natural fires, prescribed burns, and fires extinguished by firefighters affected the behavior of future fires. Many of his study plots were in areas overrun by the Whitewater-Baldy Fire. But when he revisited them after the blaze, he didn’t see a nuked forest. “To me, it’s the best-looking forest in the Southwest,” he said. “There’s a lot [fewer] trees, and the trees that are growing are big.”

  In his plots of ponderosa pines, the Whitewater-Baldy Fire—actually two fires that ignited from lightning strikes and then merged—burned away brush and grasses on the ground and killed smaller trees that crowded the woods. On the big pines that remained, the flames burned off the low branches that could carry a future fire from the ground into the treetops. As he walked through the stands opened up by the fire, Iniguez could see scorch marks 8 to 10 feet up the thick trunks of the surviving trees, which stretched into the sky like widely spaced columns. Black char on the base of the trunks made red bark higher up seem to glow. The forest canopy they held up arched some 40 feet over the researcher’s head.

  “When you’re in there, you can look and you can see a long ways,” he said. “That’s one of the cool things about the Gilas. You’re in a pine forest, but all you see is stems.”

  The parklike condition of his study plots isn’t just the result of the 2012 fire but points to the success of almost 40 years of letting fires run their natural course in the Gila—the nation’s first designated wilderness area, and the first to let wildfires burn when they didn’t threaten private property or vital resources. Where previous fires had cleared out smaller trees and brush, the Whitewater-Baldy burned with less intensity, leaving the larger, more resilient trees. In pockets where previous fires had been extinguished, the accumulated timber, brush, and grasses drove explosive fire behaviors that killed virtually every tree. At higher elevations, crown fires during the Whitewater-Baldy leveled ancient spruce-fir forests high on the Mogollon Rim, which were among the Gila’s most dramatic vistas. Those forests burned in patches twice as large as they had in recent history. But at lower elevations, the results of previous fires calmed the massive blaze.

  “All of our plots in the ponderosa pine forests did just fine,” Iniguez said. “Some of those areas have burned four times.”

  Ecologists call this type of fire “self-regulating.” According to Iniguez, “As soon as it hit the ponderosa pine belt, it went from a crown fire to a ground fire.”

  The ground fires burned with far lower intensity than the crown fires. In the ponderosa forests they left a more natural density of a few dozen widely spaced trees per acre, as opposed to as many as 1,000 crowding acres where fires had been extinguished for decades.

  Only 13 percent of the Whitewater-Baldy Fire burned hot enough to kill all the trees in an area. That’s about half the proportion that had burned with tree-killing intensity in the Las Conchas Fire the year before.13 The lower proportion of trees killed relates to another tiny percentage change. In the Gila, firefighters fight about 98 percent of lightning-ignited wildfires, while in the nation overall that figure is 99 percent. That 1 percent reduction allows about 100,000 acres a year to burn in natural wildfires, on top of some 20,000 acres of prescribed burns set by forest managers.14

  In 1995 U.S. land agencies such as the Forest Service, the Park Service, and the Bureau of Land Management, recognizing that low-intensity fires are good for the forests, agreed t
o reintroduce fire to remote wildernesses like the Gila. The cheapest and most efficient way to achieve that goal is to allow small lightning fires that seem unlikely to grow big or threaten property to burn.

  But convincing the American public—which had spent a century learning to hunt down every fire in the woods—to let these fires run wild would be more difficult than fighting the blazes.

  16

  The Fire-Industrial Complex

  Washington, D.C.—May 25, 2012

  A PIECE OF PAPER CAN IGNITE as big a fire as a lightning strike, particularly when the paper is from Washington.

  Despite the improved health of many forests where natural fires burned, two weeks after the fire in the Gila Wilderness ignited, a memo from James E. Hubbard, a deputy chief in the U.S. Forest Service, ordered “aggressive initial attack,” including on fires in the most remote wildernesses.1 Even small ground fires that improved wildlife habitat, cleaned up watersheds, and reduced the risk of big crown fires would be snuffed. The order outraged ecologists and firefighters both within and outside the Forest Service who had worked for decades to bring natural wildfires back to America’s wildernesses.

  Hubbard’s reasoning highlighted an underlying irony of wildfire management. Putting all fires out when they are small is cheaper than risking the cost of one of them growing into a big “project fire.”

  The Forest Service had exhausted its funding to fight wildfires during most years of the previous decade, and 2012 was forecast to break the budget again. Funding is based on the average of the past 10 years of firefighting costs. But with annual costs rising steeply as fire seasons became more destructive, the average trailed the yearly price tag for firefighting, and the Forest Service was virtually guaranteed to run out of funds to fight wildfires, as it had done in half the fire seasons since 2000. Putting out every fire, even remote or beneficial ones, would save money.