The Fire Next Time
by Alex Hawes
Arizona is burning. From downtown Tucson, I spot plumes of smoke drifting south from the fires atop nearby Mount Lemmon. A flyer advertises a fabulous deal on a car splotched with red slurry from a helicopter battling the blaze. Wildfires have erupted in the Huachuca Mountains and along the Mexican border near Nogales. To the north, flames lick the ponderosa pines outside Prescott. The White Mountains, one hears, are now black.
The worst of the lot—the awkwardly named Rodeo-Chediski Fire—has torched 469,000 acres of eastern Arizona pine forest, easily establishing itself as the largest fire in the state’s history. First igniting on the Fort Apache Indian Reservation, the Rodeo Fire has spread north through drought-stricken pinyon-juniper and ponderosa pine forests, eventually merging with the smaller Chediski blaze, which was set by a lost hiker.
On the eve of a firework-free Fourth of July, I meet up with Ken Frederick, a U.S. Forest Service officer, to trace the smoldering footsteps of the Rodeo inferno. We enter the charred land clad in yellow and green Nomex, a Space-Age material said to resist direct flame for up to six seconds. Small consolation. More important are our plastic helmets. Dead trees (“snags”) and dead branches—morbidly nicknamed widow-makers—can topple at a moment’s notice. While collapsing trees pose a real danger for foresters, standing snags provide prime real estate for band-tailed pigeons (Columba fasciata), acorn woodpeckers (Melanerpes formicivorus), and countless other species that descend upon a burned forest as soon as the flames recede. “It’s a big salad bar to them,” says Frederick.
Nature is nurtured by flame. Fire clears away clogged vegetation, stimulates the growth of new forbs, and creates a mosaic of habitat that can benefit a spectrum of species. “Next spring this will look great,” Frederick declares, sweeping his arm across an area where only the floor of the forest was singed. “Just watch,” he says.
Ecologists celebrate the cleansing ritual that natural fires can perform upon landscapes. They also recognize, however, that certain recent conflagrations have leapt outside the normal bounds of wildland fire behavior. The Rodeo-Chediski Fire has destroyed more than 250 homes, cost $42 million to fight, yielded $102 million in insurance claims, and put the lives of more than 4,000 firefighters and other personnel in danger. In addition, the blaze burned gaping holes into the ponderosa-pine canopy—an uncharacteristic result of wildfire in this habitat.
The suppression of wildland fire beginning a century ago has upset the order fire imposes on many ecosystems. An ensuing revolution in U.S. fire policy since the 1960s has yielded an uneven effort to restore this Promethean force and the habitat it shapes. As Ken Frederick and I descend a twisting dirt road into a rocky ravine, the mottled landscape gives way to a ghastly revelation of black. This slice of forest burned hot—the fire must have gotten up into the canopy and scorched the pines from the top down. Fallen trunks still crackle with puckish flames. Charred stumps spew forth smoke like untended stoves. I find a dead lizard in the soil—not burned, just expired. The scene conjures visions of Dante’s Seventh Circle of Hell.
Life may not return here for quite some time. Fire here has gone awry.
“ I have often remarked with how much more comfort and pleasure I could walk in woods through which a fire had run the previous year. It will clean the forest floor like a broom perfectly smooth and clear—no twigs left to crackle underfoot, the dead and rotten wood removed—and thus in the course of two or three years new huckleberry fields are created for the town—for birds and men.”
— Henry David Thoreau, June 21, 1850
About one percent of the Earth’s surface burns each year. The vast majority of the North American continent experiences the touch of flame, although the average interval between fires can range from one year to 1,000 depending upon the ecosystem. Before the arrival of flame-wielding hominids, wildland fires were usually sparked by a single mechanism: lightning. The western U.S. receives an average of 20,000 strikes each day, with the heaviest concentration occurring in summer. Lightning still accounts for an estimated 65 to 80 percent of wildfires out West. Stubborn campfires, cigarette butts, downed power lines, engine sparks, arsonists, pyromaniacs, and other artificial sources light the rest.
A budding fire can hide out in the forest litter for as many as ten days before trickling outward. Forest fires require three basic ingredients to spread: oxygen, heat, and fuel, which can take the form of tree branches, dead pine needles, grasses, and the like. Grass and loose detritus allow ground fires to spread efficiently but with low intensity. Most mature trees can survive these episodes, while younger trees and saplings die off, and the forest floor is cleared of brush. Widely spaced, “park-like” stands of trees persist.
Take fire out of the system for a few decades, however, and shade-tolerant trees begin to mature amid a tangle of other vegetation. What you have now are the makings of a firestorm. When a flame—natural or otherwise—sparks in a dense thicket like this, shrubs, saplings, and low-lying branches act as "ladder fuels” that carry fire into the upper reaches of the forest, where it can spread among the canopy layer, becoming a crown fire. Crown fires can incinerate even the most thick-skinned giants of the forest, forging history and nightmares. The 1967 Sundance Fire in Idaho—a crown fire that razed 50,000 acres in just nine hours—generated the energy of a Hiroshima-force atomic bomb exploding every two minutes, according to fire historian Stephen Pyne of Arizona State University.
Yet even such fiery cataclysms yield amazingly few animal mortalities. State biologists conducted a one-day survey of the Rodeo-Chediski burn area shortly after the blaze was contained. The census recorded three dead elk (Cervus elaphus), two dead black bears (Ursus americanus), but few other remains across the 200 miles the surveyors traveled. (They did spot numerous live elk, deer, song-birds, hawks, woodpeckers, lizards, and even feral horses.) Over the following month, officials found only 38 elk carcasses across nearly a half-million burned acres. Hundreds of other elk had simply scurried around—and occasionally through—the flames unharmed. The true test will come this winter, as elk and other herbivores in the White Mountains struggle to find enough forage amid the ash. The Yellowstone Fires of 1988 killed about one percent of the area’s elk directly, but as much as 40 percent of the population died off during the following winter.
Smaller animals, such as rodents and snakes, burrow underground to escape smoke and flames. Although fire can suck oxygen out of these holes and suffocate some creatures, most animals survive all but the worst conflagrations if they can tunnel several inches below the surface. The most vulnerable animals during forest fires are mothers who are encumbered by young, or species such as the Abert’s squirrel (Sciurus aberti), whose instinct in the face of danger is to retreat to the treetops and remain still.
Following a fire, animal life rearranges and reestablishes itself. After the 1988 Yellowstone Fires, coyotes (Canis latrans), grizzly bears (Ursus arctos), bald eagles (Haliaeetus leucocephalus), and other carnivores quickly scavenged whatever carcasses remained. Northern three-toed woodpeckers (Picoides tridactylus) hunted for bark beetles in the snags, creating holes later inhabited by mountain bluebirds (Sialia currucoides) and other secondary cavity nesters. Fire forced open lodgepole pine cones, dispersing seeds for Clark’s nutcrackers (Nucifraga columbiana) and pine siskins (Carduelis pinus). Beavers (Castor canadensis) feasted on new aspen growth.
Burning also increases the crude protein content and palatability of grasses and forbs during the first year after a fire, improving forage for elk, bison (Bison bison), and mule deer (Odocoileus hemionus). The only vertebrate species known to have suffered a long-lasting decline as a result of the Yellowstone Fires is moose (Alces alces), which has struggled to find sufficient willow and subalpine fir for winter forage.
Plants, being mostly immobile, rely on a bit more evolutionary creativity to outlast a raging blaze. The thick bark of the mature ponderosa pine and Douglas fir protects the cambium—the fragile layer between the bark and wood that transports water and vital nutrients—from the heat of moderate-intensity fires. Certain fire-hardy plants, especially in chaparral habitat, bear highly flammable chemicals that actually encourage the spread of fire—and the destruction of less fire-resistant plant competitors. Trees such as giant sequoias and lodgepole pines develop serotinous cones, sealed shut by resin, that open up and release seeds only when intensely heated by flame. Wildfire conveniently clears away open space where these seeds can germinate in direct sunlight and nutrient-rich ash. Gambel oaks quickly regenerate after fire via underground stems, or rhizomes—as does fireweed, whose mauve flowers are often the first to brighten a burn site. Aspen’s frail, paper-like bark is little match for fire, but the tree readily re-sprouts from shallow, lateral roots. Various forb species soon burst forth from long-dormant seeds.
Fire provides a coming-out party, complete with charcoal. The corollary principle is that, in the absence of fire, these plant species—and their animal dependents—may eventually become absent themselves.
“ We are the fire that burns the country.”
— Bantu proverb
The control of fire, anthropologists surmise, likely hastened human evolution and dispersal. In North America, indigenous tribes revered this life-force as “our Grandfather Fire.” Native Americans ignited flames to flush bears from dens; to thin out forests in order to better spot deer; to drive away mosquitoes and bees; to stimulate grassland growth; to communicate with friends; to encircle enemies. So crucial was fire that the Narragansett Indians assumed the English had come to America in search of firewood.
Thanks in part to Native Americans using fire to turn forests into grassland, bison were able to expand their range as far east as Massachusetts by the 17th century. Following the forced removal of Native Americans from much of the continent by European colonists and, later, by the U.S. government, prairie gave way again to pine forests in the South, to pinyon and juniper forests in the Southwest, and to sagebrush in the Great Basin. “The transformation of grasslands, prairies, and savannahs to forests is one of the most fundamental and widespread outcomes of European colonization,” writes Stephen Pyne in Fire in America.
Native Americans passed on many of their forest-burning techniques to white farmers. It was the defense of timber, not farmland, that eventually beckoned the United States to declare war on fire. Appointed in 1898, Gifford Pinchot, the nation’s first Chief Forester, advocated “wise use” of federal forests to preserve natural resources. His conservationist philosophy advocated not only limiting uncontrolled logging but also quashing wildland fire in all forms.
The U.S. Forest Service (USFS) faced its first real trial on August 20 and 21, 1910, when hurricane-force winds in northern Idaho and western Montana united hundreds of smaller fires into a maelstrom beyond even Dante’s imaginings. The Great Idaho Fire of 1910, or simply “the Big Burn,” ravaged three million acres in the Northern Rockies, killed at least 85 people, and erased entire towns from the map. Rather than draw ire to the agency, however, the Big Burn provided the USFS with both purpose and prominence. Pinchot’s successor, Henry Graves, soon declared firefighting “the fundamental obligation of the Forest Service [which] takes precedence over all other duties and activities.”
The development of modern firefighting techniques and technology, including telephone-equipped lookout towers, fire roads cut into the wilderness, airplanes disgorging Smokejumpers, and flame-retardant slurry allowed federal foresters, with the help of the Civilian Conservation Corps, to achieve all too well their “10 A.M. Policy” of putting out wildfires by the morning following a fire’s discovery. An average year in the 1930s saw more than 39 million acres of the U.S. charred by flame; by the 1960s that figure had dropped to fewer than five million, according to the National Interagency Fire Center (NIFC). Still, the fires came. The costs were building, and so too were the fuels.
In the hot corners of the country, a few scientists and foresters surreptitiously continued to play with fire. Beginning in 1909, Yale University forestry biologist H.H. Chapman—the first true champion of controlled burning—performed research demonstrating that southern pines rely on fire to suppress hardwood competitors, reduce hazardous fuel buildup, and stave off brown-spot disease. In 1931, Herbert L. Stoddard of the Tall Timbers Research Station in Tallahassee, Florida, published an article arguing that fire in the long-leaf pine ecosystem was particularly vital for the northern bobwhite (Colinus virginianus). (Today, prescribed fire is being used to restore Sonoran grasslands for the masked bobwhite, Colinus virginianus ridgwayi, the northern bobwhite’s endangered cousin.) Another vocal advocate of fire’s importance, Harold Biswell of the University of California at Berkeley, almost got kicked out of the School of Forestry in 1950 for his pyromantic musings. Biswell later proved that sequoias depend on fire to kill the seeds of neighboring trees.
The naturalist Aldo Leopold—who died, ironically, while helping neighbors battle a grass fire in 1948—wondered whether fighting wildfire was even worth the government’s effort. But it was Aldo’s son who had a far greater role in rekindling the flames. A. Starker Leopold headed a federally appointed committee charged with re-examining management procedures in the national parks. The Leopold Report, released in March 1963, declared, “A national park should represent a vignette of primitive America.” One key tool the committee recommended for restoring this pre-Columbian vision was prescribed burning. The government’s attitude toward fire had suddenly shifted east to west.
“ Behold, how great a matter a little fire kindleth!”
— Epistle of James, Chapter III, verse five
The frequency and intensity of wildland fire—known as a fire regime—varies dramatically from habitat to habitat. Historically, fires on a given patch of Missouri prairie raged every year, those in alpine tundra or in New England balsam forest every millennium on average. Through a prism of flame, the workings of elaborate ecosystems can be discerned, and perhaps rejuvenated.
Fire is no stranger to the land charred by the Rodeo blaze, being home to the largest stand of ponderosa pine on the planet. Ponderosa pine relies on fire to remove shade-tolerant Douglas-fir and spruce competitors. The pine’s thick, puzzle-piece bark insulates its cambium, while its lower limbs drop off during its growth to prevent flames from climbing into the canopy. Grasses interspersed between mature pines normally transport low-intensity fires ignited by the Southwest’s frequent lightning storms. These modest burns yield a mosaic of thin, open forest—offering good perches and sightlines for raptors like the sharp-shinned hawk (Accipiter striatus), the northern goshawk (Accipiter gentilis), and the threatened Mexican spotted owl (Strix occidentalis lucida).
However, livestock ranching over the past century has removed much of the grass cover, encouraging the build-up of woody growth, and yielding either no fire—or crown fire. “Blaming it all on fire suppression would be a mistake,” says Stephen Pyne. “In the Southwest, it begins with grazing.”
A similar story is told on the opposite coast. Once covering several million acres of sandy coastal plains in the Southeast, longleaf pine forests have been reduced to two percent of their former reign. The removal of fire is partly to blame. As elsewhere, southern pines can resist fire better than their hardwood competitors. Historically, the forest is bathed in flame every two to five years on average. Many birds that evolved in this particular fire regime vanish after only five years of fire suppression.
The endangered red-cockaded woodpecker (Picoides borealis) inhabits longleaf as well as loblolly and shortleaf pine forests. Understory fires are essential to prevent the development of hardwood mid-story growth; without such fires, these birds will abandon their territory. Red-cockaded woodpeckers today are found predominantly in areas with a history of aggressive, prescribed burning. In addition, understory burning increases populations of arthropods—many of which breed and feed in charred trees—likely aiding insectivorous loggerhead shrikes (Lanius ludovicianus) and American kestrels (Falco sparverius). Threatened gopher tortoises (Gopherus polyphemus) also benefit from the open ground-cover afforded by burning in longleaf pines.
The salve of flame extends beyond the forests. Wildfires allow grasslands to beat back the invasion of trees and shrubs. Prairie blazes burn the tops of grassy plants, leaving healthy roots to regenerate amid the fertilizing ash. Fire exclusion, however, has encouraged the encroachment of woody vegetation, fragmenting tallgrass prairie habitat for a host of species, most notably the greater prairie-chicken (Tympanuchus cupido) and Henslow’s sparrow (Ammodramus henslowii).
The chaparral (scrub oak) habitat of southern California ranks among the most explosive fire regimes on the planet. Wildfires tear through this habitat every 20 to 25 years, fueled by oils and resins in many local plants, and by the hot, dry Santa Ana winds. These conflagrations suit the wild inhabitants just fine. Laurel sumac, big berry manzanita, lemonade bush, and other typical chaparral plants require fire to germinate. Without fire, deer and ground-dwelling birds have trouble foraging amid the dense scrub. The endangered California condor (Gymnogyps californianus) nearly went extinct; this was due, in part, to the havoc wrought by wildland fire’s absence. As the chaparral vegetation grew ever thicker, condors had trouble spotting rabbits and other small mammal prey, which themselves thrive in a landscape periodically renewed in flame. But with real estate properties pushing ever farther into California’s sun-baked scrubland, the pressure to suppress fire here continues.
“A stand-replacing fire is nature’s reset button,” says Ken Frederick. “It takes the forest back to an early successional stage, to start over.” But public tolerance for inferno can stretch only so far.
“…flame is not a kind of ecological pixie dust that, sprinkled over the land, will transform the bad and ugly into the good and beautiful. Messed-up forests only yield messed-up fires.”
— Stephen Pyne, “The Big Blowup”
In the spring of 2000, the Cerro Grande Fire torched 48,000 acres of northern New Mexico’s Jemez Mountains, forcing the evacuation of 18,000 people, destroying more than 235 homes, and causing more than $1 billion in damage. The fire was not only lit by human hands—but by federal foresters performing a prescribed burn in Bandelier National Monument. High winds and dry fuels following a La Niña winter thrust the flames outside their established boundaries and sent scientists at Los Alamos National Laboratory scurrying for cover.
A pristine ponderosa pine forest, in theory, should hold 40 to 150 pines per acre. In some areas of the Jemez Mountains today, more than 2,000 ponderosa pines are squeezed into an acre of canopy, a result of decades of fire suppression. Controlled burns can either reduce these fuels—or cause the fuels to explode.
“We’ve pretty well run over the woods,” argues Stephen Pyne. “The land has changed so much that putting fire back into it would be like dumping wolves into a shopping mall.” Pyne argues that forest thinning—the mechanized removal of trees done either by the U.S. Forest Service or contract loggers—is necessary in areas where the build-up of fuels precludes controlled burning. But many environmentalists are suspicious that thinning projects give commercial loggers an excuse to strip the forest of its most precious assets under the guise of forest restoration.
“Old-growth ponderosa pine forest is in short supply,” says Craig Gehrke of the Wilderness Society. “If it comes down to losing the big trees to save the forest, I’m not sure that’s an equitable trade.” The most sought-after component of the forest—the lofty, centuries-old trees—are also the least flammable and the most important ecologically. Removing mature, old-growth trees during thinning operations makes little or no sense from a fire-prevention perspective. From an economic perspective, however, timber companies arguably can’t make a profit without harvesting at least some larger-diameter trees, and the Forest Service lacks the budget to perform thinning operations on its own.
The Bush Administration recently announced its intentions to ease regulations on logging in national forests in order to reduce fuels. Currently, the USFS is planning a thinning project outside Flagstaff that would allow contractors to extract 6,000 large-diameter ponderosa-pines to help offset the costs of thinning a modest 10,400 acres of forest. However, an estimated 1.2 million acres of overgrown ponderosa-pine timberland surround Flagstaff. Something must give before the next conflagration ignites.
“To the best of our knowledge, the burning of these high-intensity fire patches are off the scale. They’re historically anomalous,” says Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona. Swetnam has studied centuries of tree-ring data from the Southwest to unlock pre-colonial fire regimes in ponderosa-pine forests and other habitats. Fires occurred with great regularity here thanks to the ubiquity of lightning, but Swetnam can find nothing to suggest Rodeo-style blazes torching the landscape before the double-whammy introduction of livestock grazing and fire suppression. “You don’t see evidence of those kinds of 1,000- to 10,000-acre holes in the canopy burning at these elevation before the 1950s,” he says.
Far less well understood is how these monster fires—the offspring of 20th-century forestry and grazing activities—are affecting wildlife. Species with highly restricted ranges are inherently vulnerable to catastrophic blazes. In 1916, the world’s remnant population of 2,000 heath hens (Tympanuchus cupido cupido) was confined to the island of Martha’s Vineyard when a scrub fire sent them on the road to extinction. The 1990 Dude Fire, which struck just west of the site of the Rodeo-Chediski Fire, wiped out a small population of thick-billed parrots (Rhynchopsitta pachyrhyncha), temporarily ending a reintroduction project for that species in Arizona. Severe fires today might destroy critical nesting trees for threatened Mexican and California spotted owls (Strix occidentalis occidentalis); only time will tell how Mexican spotted owls fare in the wake of the Rodeo Fire.
Crown fires can also sterilize the soil and cause erosion of silt and ash into streams and rivers, altering their water chemistry and temperature. This influx of nutrients can either spawn algal growth and, in turn, buoy aquatic invertebrates and native fish—or overwhelm the ecosystem entirely. Arizona state biologists are monitoring the effects of the Rodeo-Chediski Fire on the threatened Little Colorado River spinedace (Lepidomeda vittata). The 1994 Rattlesnake Fire in the Chiricahua Mountains nearly eliminated the Mexican stoneroller (Campostoma ornatum) from Rucker Canyon, the small minnow’s only foothold in Arizona. The Dude Fire, on the other hand, presented the Arizona Game & Fish Department with an opportunity: after erosion killed off rainbow trout (Oncorhynchus mykiss) and other non-native sports fish, state officials reintroduced native Gila trout (O. gilae). State biologists have literally tens of thousands of native Apache trout (O. apache) in fish hatcheries awaiting reintroduction if post-Rodeo conditions permit.
Invasive species can interact with fire in more troubling ways. Russian thistle—better known as tumbleweed—was first introduced to America from the Siberian steppes in 1873. As the plant dries, the base of the stem becomes brittle and breaks off, dispersing thousands of seeds as it topples in the wind. Wildfires can spread rapidly when tumbleweed firebrands roll through grasslands. More alarmingly, cheatgrass, another Russian import, has taken advantage of its fire-tolerance to conquer the Great Basin, bringing flames in and pushing native plants like sagebrush—which requires as much as 50 years to recover from wildfire—out. So far, the invasion of cheatgrass is known to have harmed populations of mule deer and pronghorn (Antilocapra americana)—which avoid eating the plant—as well as sage grouse (Centrocercus urophasianus), Townsend’s ground squirrel (Spermophilus townsendii), prairie falcon (Falco mexicanus), golden eagle (Aquila chrysaetos), and several other species.
Exotic grasses are also summoning fire into the Sonoran Desert, an ecosystem that U.S. Geological Survey (USGS) ecologist Cecil Schwalbe calls “essentially naïve to fire.” A herpetologist by training, Schwalbe has studied the impact of Mediterranean red brome and African buffelgrass on desert tortoises (Gopherus agassizi), saguaro cactus, and other Sonoran species. Ranchers originally planted buffelgrass on millions of acres in northern Mexico for cattle forage. The grasses spread, and with them wildfire. A single blaze, the 1994 Mother’s Day Fire in Saguaro National Park, burned 340 acres of prime desert tortoise habitat, killing 11 percent of the adult tortoise population there. (The normal mortality rate of desert tortoises, Schwalbe cautions, is only two percent a year.) The Mother’s Day Fire also killed more than 20 percent of the saguaro cacti over the course of the next five years—destroying food and shelter for a host of desert species.
“Because buffelgrass resprouts vigorously after fire, it is capable of causing more frequent and larger wildfires,” said Todd Esque, Schwalbe’s research collaborator at USGS, during a recent Ecological Society of America conference in Tucson. “These changes could potentially convert Sonoran Desert shrublands to exotic fire-driven grasslands, completely altering the kinds of plants in the Sonoran Desert and even eliminating saguaros in some areas.”
One positive outcome of the landmark 2000 fire season has been Congressional passage of the National Fire Plan, which has allocated $1.9 billion to help minimize the impact of invasive species following fires, as well as to rehabilitate burned forests, reduce hazardous fuels, and rebuild communities. The plan also aims to educate the growing number of homeowners who live in areas susceptible to wildfire.
“We need to move the discussion away from the simple orthodoxy that natural fire is good to a new debate to begin talking about where fire is necessary, where it’s optional, and where it’s too dangerous,” says Stephen Pyne. “That doesn’t seem too difficult to do.”
Little by little, our society is learning to live with—if not love—fire. Amid the smoke, one thing is clear: The fires will return, and we must be ready.
“And God gave Noah the rainbow sign.
No more water, the fire next time.”
—Alex Hawes, a former Associate Editor of ZooGoer, moved to Tucson last spring—just in time for record heat, record drought, and record fire.
ZooGoer 31(6) 2002. Copyright 2002
Friends of the National Zoo.
All rights reserved.