The Great Fires Of 1988

Information , pictures,and text provided courtesy of Yellowstone National Park

    Landscapes such as those seen in Yellowstone have long been shaped by fire and not just the cool, creeping ground fires often described as "good" for grass production. The natural history of fire in the park includes large-scale conflagrations sweeping across the park's vast volcanic plateaus, hot, wind-driven fires torching up the trunks to the crowns of the pine and fir trees at several hundred-year intervals.

    Such wildfires occurred across much of the ecosystem in the 1700s. But that, of course, was prior to the arrival of European explorers,  and the pattern established by its early caretakers to battle all blazes in the belief that fire suppression was good stewardship. Throughout much of the 20th century, park managers and visitors alike have continued to view fire as a destructive force, one to be mastered, or at least tempered to a tamer, more controlled entity. By the 1940s, ecologists recognized that fire was a primary agent of change in many ecosystems, including the arid mountainous western United States.

    In the 1950s and 1960s, national parks and forests began to experiment with controlled burns, and by the 1970s Yellowstone and other parks had instituted a natural fire management plan to allow the process of lightning-caused fire to continue influencing wildland succession.
 
 

Many of Yellowstone's plant species are fire-adapted. Some (not all) of the lodgepole pines (Pinus contorta), which make up nearly 80% of the park’s extensive forests, have cones that are serotinous sealed by resin until the intense heat of fire cracks the bonds and releases the seeds inside. Fires may stimulate regeneration of sagebrush, aspen, and willows, but the interactions between these plants and fire is complicated by other influences such as grazing levels and climate. Though above-ground parts of grasses and forbs are consumed by flames, the below-ground root systems typically remain unharmed, and for a few years after fire these plants commonly increase in productivity.
 

    In the first sixteen years of Yellowstone's natural fire policy (1972-1987), 235 fires were allowed to burn 33,759 acres. Only 15 of those fires were larger than 100 acres, and all of the fires were extinguished naturally. Public response to the fires was good, and the program was considered a success. The summers of 1982-1987 were wetter than average, which may have contributed to the relatively low fire activity in those years.
 

    No one anticipated that 1988 would be radically different. In April and May, Yellowstone received higher-than normal rainfall. But by June, the greater Yellowstone area was experiencing a severe drought. Forest fuels grew progressively drier, and the early summer thunderstorms produced lightning without rain. The fire season began, but still without hint of the record season to come. Eleven of 20 early-season fires went out by themselves, and the rest were being monitored in accordance with the existing fire management plan.
 
 
 

The summer of 1988 turned out to be the driest in the park's recorded history. By July 15, only 8,500 acres had burned in the entire greater Yellowstone area. Still, due to continued dry conditions, on July 21 by which time fire activity had become noticeable to park visitors and to the national media the decision was made to suppress all fires. But within a week, fires within the park alone encompassed more nearly 99,000 acres, and by the end of the month, dry fuels and high winds combined to make the larger fires nearly uncontrollable. National news reporters poured into Yellowstone National Park, as did firefighters from around the country, bolstered by military recruits. On the worst single day, August 20, 1988, tremendous winds pushed fire across more than 150,000 acres.

 

Throughout August and early September, some park roads and facilities were closed to the public, and residents of nearby towns outside the park feared for their property and their lives. Yellowstone's fire management policy was the topic of heated debate, from the restaurants of park border towns to the halls of Congress.
 

    By September 11, 1988, the first snows of autumn had dampened the fires as the nation's largest fire-fighting effort could not. The imminent danger to life and property was over, and firefighters were gradually sent home, although the last of the smoldering flames were not extinguished until November. Staff in Yellowstone National Park went to work surveying the impacts of the fires on wildlife, plants, historic structures, trails, and more and answering the demands for information, explanation, and a new fire management policy.
 
 
 

A total of 248 fires started in greater Yellowstone in 1988; 50 of those were in Yellowstone National Park. Despite widespread misconceptions that all fires were initially allowed to burn, only 31 of the total were; 28 of these began inside the park. In the end, 7 major fires were responsible for more than 95% of the burned acreage. Five of those fires were ignited outside the park, and 3 of them were human-caused fires that firefighters attempted to control from the beginning. More than 25,000 firefighters, as many as 9000 at one time, attacked Yellowstone fires in 1988, at a total cost of about $120 million. Thankfully, the fires killed no park visitors and no nearby residents. Outside the park, two firefighters were killed, one by a falling tree and one while piloting a plane transporting other personnel.
 

    Ecosystem wide, about 1.2 million acres was scorched; 793,000 (about 36%) of the park’s 2,221,800 acres were burned. Sixty-seven structures were destroyed, including 18 cabins used by employees and guests and one backcountry patrol cabin in Yellowstone. Estimated property damage totaled more than $3 million. About 665 miles of hand-cut fireline and 137 miles of bulldozer lines, including 32 miles in the park, needed some rehabilitation, along with the remnants of fire camps and helicopter-landing spots. Surveys found that 345 dead elk (of an estimated 40,000-50,000), 36 deer, 12 moose, 6 black bears, and 9 bison died in greater Yellowstone as a direct result of the fires; 2 radio-collared grizzly bears were missing and were presumed to have been killed, (although one turned up alive and well several years later). Most of the animals that died were trapped as fire quickly swept down two drainage's, and were discovered when biologists subsequently observed scavenging grizzlies, coyotes, and birds feeding on the carcasses. A few small fish-kills occurred as a result of either heated water or dropping fire retardant on the streams. Surveys revealed that less than 1% of soils were heated enough to burn below-ground plant seeds and roots.
 
 
 

A massive effort was funded by the U.S. Congress to restore damaged facilities and to study the long-term ecological, social, and economic effects of the Yellowstone fires. Although the tourist season was cut prematurely short by the fires and associated firefighting activity, the feared abandonment of regional visitors failed to materialize in 1989. The effects on many plants and animals are still being studied, although in the short-term, most wildlife populations showed no effect or rebounded quickly from the fiery summer. In the several years following1988, ample precipitation combined with the short-term effects of ash and nutrient influx to make for spectacular displays of wildflowers in burned areas. And, where serotinous lodgepole pines were burned, seed densities ranged from 50,000 to 1 million per acre, beginning a new cycle of forest growth under the blackened canopy above.
 

    Across the nation, national parks and forests suspended and updated their fire management plans, assisted by the ecological assessment of a panel of independent scientists and by revised national fire management policies. In 1992, Yellowstone National Park again had a wildland fire management plan, but with stricter guidelines under which naturally occurring fires may be allowed to burn.
 

    Although unprecedented in the 125-year history of the park, the scientists reviewing the effects of the 1988 fires reminded us that fires of such scale burned elsewhere in similar ecosystems during this century, and earlier in the landscape's history.
 
 

Fire Ecology

    The history of wildfire in Yellowstone is long and varied.  Even before written records of fire with the advent of Yellowstone National Park in 1872 we see evidence of fire in soil profiles, lake sediments, land slides, and in old-growth trees that have been scarred by fire.  It is clear that wildfire has had a role in the dynamics of Yellowstone's ecosystems for  thousands of years.
 

    Although many fires were caused by human activities, most ignitions were undoubtedly natural. The term "natural ignition" is nearly synonymous with a lightning strike.  Afternoon thunderstorms occur frequently in the Northern Rockies but release little precipitation, a condition known as dry lightning.  In a typical season there are thousands of lightning strikes in Yellowstone.  Lightning strikes are powerful enough to rip strips of bark off of a tree in a shower of sparks, and blow the pieces up to 30 meters (100') away.  However most lightning strikes never result in a wildfire because fuels are not in a combustible state.
 

    Fuels are typically wood, foliage or grass.  Fuels may be fine, such as twigs and needles, or heavy, such as logs, branches and whole trees that have blown down in a storm.  Fuels may also be living such as an understory layer of tree regeneration or a layer of shrubs.
 

    In order for an ignition to take place, the fuels must be dry.  As spring advances into summer, temperatures increase and the relative humidity decreases-- factors which dry fuels.
 

On average in Yellowstone, fuels dry out enough to ignite the first wildland fire of the year about the middle of June.
 

    Young forests generally do not have the fuel load that mature and old-growth forests do. Many young stands of  trees are regenerating old burns and consequently haven't had time to accumulate fuel.  However, as a stand develops it accumulates fuel:  needle-cast, fallen branches, lichens, and logs.  As the young trees grow they compete for light and other resources.  Many don't survive the competition, and remain in the  stand as standing dead snags which fall over and further contribute to the fuels on the forest floor.
 

    As trees grow they also "self-prune" old branches that become shaded by new foliage at the top of the canopy.  These pruned branches eventually fall off the tree and accumulate as litter on the ground.  As the stand grows older and taller the canopy begins to break up, letting light reach the forest floor and allowing the establishment of an understory layer of shrubs and regenerating trees.  This understory layer forms a "ladder" of fuel that may allow a ground fire to ascend into the forest  canopy.  This accumulation of fuel on the forest floor and the continuity of fuels between the ground, understory and overstory are factors that predispose older stands to ignition by a lightning strike.
 

Nearly all of Yellowstone's plant communities have burned at one time or another.  Some plant communities ignite and carry fire more readily than others.  Therefore the "fire regime" of Yellowstone is as varied and complicated as the environments within the park.  It must be remembered that any forest will burn provided an ignition during periods of prolonged drought, high temperatures, low relativity humidity or high winds.  However each type of forest has certain characteristics that cause wildfires to behave differently.  Some trees such as Douglas-fir have very thick bark that insulates the tree against heat.  The  bark protects the cambium (the water and nutrient conducting system between the bark and the wood) which will die if it is exposed to temperatures greater than 60°C (140°F) for longer than 1 minute (Agee 1993).  Thick bark ensures that wildfires seldom to kill mature Douglas-fir trees.
 

    Other species such as lodgepole pine, whitebark pine, Engelmann spruce and subalpine fir have thin bark but these species have other adaptations to fire.  Lodgepole pines have cones that are serotinous; that is, they  are glued shut by resin.  The heat of a wildfire is needed to melt the resin and allow the cone to open and disperse the seeds within. This adaptation ensures that the seeds of lodgepole pine will not disperse until wildfire creates conditions that favor the establishment of seedlings-- diminished litter on the forest floor and plenty of sunlight.
 

    Although whitebark pine, Engelmann spruce and subalpine fir are also thin-barked, they are adapted to fire by escaping.  That is, they grow in habitats that are less susceptible to wildfire.  Whitebark pines grow in open, cold, high altitude habitats that accumulate fuel very slowly. The length of the growing season between snowmelt and snowfall, and the cooler temperatures leave a short seasonal window in which wildfires can ignite and carry. Engelmann spruce and subalpine fir grow in cool, moist habitats where conditions that enable wildfires to burn are infrequent.
 

    Aspen also has thin bark and low tolerance to fire but it readily regenerates by sprouting. Aspen clones are connected by a network of roots which survive even very hot fires because they are insulated underground.  Although the above-ground stems may be killed by fire the roots send up a profusion of sprouts in the following years.
 

    Fire ecologists use estimates of fire return intervals to better understand the role of fire in different forest types.  Fire return intervals represent the average frequency of fire for an area or plant community type on the landscape.  Natural, historical fire return intervals in Yellowstone range from 20-25 years for shrub and grasslands in the Northern Range (Houston 1973) to 300 years or more for lodgepole pine forests on the central plateau (Romme 1982, Romme and Despain 1989) and subalpine whitebark pine stands.
 
 
 
 

Houston, D.B. 1973. Wildfires in Northern Yellowstone National Park. Ecology 54(5):
1111-1117.

Romme, W.H. 1982. Fire and landscape diversity in subalpine forests of Yellowstone
National Park. Ecological Monographs 52(2): 199-221.

Romme, W.H. and D.G. Despain. 1989. Historical perspective on the Yellowstone Fires of
1988. Bioscience 39(10): 696-699.

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