Fire environment, fire regimes and the ecological role of fire
There have been several different systems used in classifying fire regimes in the United States (Heinselman 1978; Agee 1993; Morgan et al. 1998; and Frost 1998). Brown and Smith (2000) classified fire regimes based on fire severity. Use of fire severity as the key component in describing fire regimes is appealing because it relates directly to the effects of disturbance, especially on survival and structure of the dominant vegetation. Brown and Smith (2000) described fire regimes as follows:
Understory fire (applies to forests and woodlands)–fires are generally non-lethal to the dominant vegetation and do not substantially change the structure of the dominant vegetation. This fire regime typically applies to the 39 million acres of ponderosa pine in the western U.S. where fires historically occurred every 10-15 years as low-intensity surface fires. Southern pines in the southeast U.S also belong in this fire regime.
Mixed-severity fire (applies to forests and woodlands)– the severity of fire either causes selective mortality in the dominant vegetation, depending on different tree species’ susceptibility to fire, or varies between understory and stand replacement. Lodgepole pine in the western U.S. fits in this regime because fires can be characterized as both understory surface fires in younger stands and later as stand replacement crown fires in older stands.
Stand replacement fire (applies to forests, woodlands, shrublands and grasslands)–fires kill aboveground parts of the dominant vegetation, changing the aboveground structure substantially. Approximately 80 percent or more of the aboveground dominant vegetation is either consumed or dies as a result of fires. Plant communities in this regime include chaparral in California, sagebrush in the Interior West, grasslands in the Great Plains and spruce-fir forests in the West.
Non-fire regime–little or no occurrence of natural fire. Most plant communities in the U.S. fall into one of the three previous fire regimes. Sitka spruce in Alaska, however, would fall into the non-fire regime class, because fires are rare or absent in this wet environment.
Narrative summary of major wildfire impacts on people, property and natural resources that occurred historically
The Peshtigo, Michigan, Hinckley, Yacoult and Maine fires burned hundreds of thousands of hectares and killed more than 2000 people between 1871 and 1947. On the same day, October 8, 1871, that fire wiped out the town of Peshtigo, Wisconsin, the great Chicago fire devastated urban Chicago. Comparative statistics for those two fires highlight the destructive potential of wildland fires. The Peshtigo fire covered 518,016 hectares and killed 1150 people, whereas 860 hectares burned and 300 lives were lost in the Chicago fire. The 1910 wildland fires in northern Idaho and Montana had several common elements: many uncontrolled fires burning at one time; prolonged drought, high temperatures and moderate to strong winds; and mixed conifer and hardwood fuels with slash from logging and land clearing. These large fires occurred primarily in conifer forests north of the 42nd meridian, or roughly across the northern quarter of the contiguous United States. One critical element, which is not as likely to occur today as formerly, was the simultaneous presence of many uncontrolled fires. The effectiveness of modern fire suppression organizations has been greatly enhanced by their rapid growth and by the air deployment of firefighters and retardants to even the most remote wildland locations. High-velocity winds and more than 1700 individual fires contributed to the spread of the 1910 fires.
Prolonged drought, high winds and flammable fuel types, however, are as significant to the behavior of high-intensity fires today as previously. In 1967 the Sundance fire in northern Idaho burned more than 22,627 hectares and killed two firefighters (Anderson 1968). In 1970, other fires burned approximately 40,470 hectares near Wenatchee, Washington. During the drought-stricken 1977 fire season in California, 21 major fires burned almost 150,000 hectares. The largest of these fires, the remote Marble Cone, spread through 70,418 hectares (174,000 acres) of flammable chaparral and mixed forest. The Sycamore fire near Santa Barbara, California, although only 324 hectares in size, destroyed more than 200 homes.
The benefits accrued by decreasing the number of uncontrolled fire starts have been offset by the tendency of people to live in fire-prone areas. For example, some of the fires most potentially damaging to human lives and property occur in areas rich in chaparral shrub fuel in California. Several wildfires in southern California in 1970, fuelled by a prolonged drought and fanned by strong Santa Ana winds, produced 14 deaths, destroyed 885 homes and burned more than 242,820 hectares. Ten years later the situation recurred over 28,330 hectares in southern California, resulting in the deaths of 5 persons and loss of more than 400 structures.
Wildland fires that threaten human lives and property are not exclusively located in southern California, since the exodus to wildland regions has become a national phenomenon. Fires burned more than 80,940 hectares in Maine in October 1947, killing 16 people; another 80,940 hectares burned in New Jersey in 1963. On July 16, 1977, the Pattee Canyon fire in Missoula, Montana, destroyed 6 homes and charred 486 hectares of forests and grasslands in only a few hours.
The 1985 wildland fire season was one of the most severe in this century. The national toll for that year paints a stark picture: 44 civilians and firefighters died, 1400 homes and structures were destroyed or damaged and 1.2 million hectares were burned. On one day in Florida, May 17, a firefighter died, 40,470 hectares burned, 600 homes and other buildings were destroyed or damaged and more than 1000 residents were safely evacuated. During 1986, in three states alone, wildfires forced 13,500 people to evacuate their homes.
A human-caused fire, starting on July 9, 1989, near Boulder, Colorado, raced through residential areas among the trees, destroying 44 homes and other structures and burning over 850 hectares. Losses for homes and natural resources were estimated at $10 million and the cost to control the fire was another $1 million. This Black Tiger fire produced the worst fire losses in Colorado’s history. The causes were familiar: lack of rainfall, high temperatures, strong winds, steep topography, buildup of forest fuels, construction factors affecting the susceptibility of the homes to fire, combustible construction materials, poor access for emergency vehicles and lack of home site maintenance for fire protection. The conditions that led to the Black Tiger fire are still prevalent in many parts of Colorado as well as in other states.
Narrative summary of major wildfire impacts on people, property and natural resources during 1990-2000
This narrative summary of wildfire impacts was compiled from reports maintained by the National Interagency Fire Center in Boise, Idaho.
A wildfire in Arizona in 1990 resulted in the death of six firefighters who were overrun as they were attempting to protect a group of homes. In late June California experienced extreme fire behavior on several fires due to dry conditions and high winds. Over 500 structures and two shopping malls were destroyed. Air tankers were in short supply, necessitating the activation of eight military C-130s equipped with airborne retardant delivery systems and three airtankers from Canada. In August, dry lightning storms occurred in northern California, Oregon, Washington and the Great Basin, calling for the mobilization of hundreds of firefighters and other firefighting resources. By August 9 all domestic firefighting resources were fully committed and the military was asked to provide personnel to be trained to assist with the fire emergency.
The 1992 fire season was dominated by the El Niño weather phenomenon. Most El Niño episodes produce a split flow in the upper air pattern west of the Pacific Coast. This produces above normal precipitation over the southern United States and drier than normal conditions in the Pacific Northwest and Great Basin. From October 1991 to April 1992, the Pacific Northwest received 50 to 70 percent of normal precipitation, while the Desert Southwest and the southern states received up to 150 percent of normal precipitation. The Foothills Fire started near Boise, Idaho, in late August on a Bureau of Land management area and quickly burned into ponderosa pine forests on the Boise National Forest. This fire grew to 257, 600 acres before it was controlled, making it the largest wildfire of the year. Where it burned into the overly dense ponderosa pine forest, it burned as a stand replacement crown fire and killed most of the trees over a 70,000-acre area.
On 20 October 1992, a devastating fire occurred in the hills above Oakland and Berkeley, California. Burning embers carried by high winds from the perimeter of a small fire resulted in a major wildland/urban interface conflagration that killed 25 people, injured 150 others and destroyed nearly 2449 single-family dwellings and 437 apartment and condominium units. It burned over 648 hectares and did an estimated $1.5 billion in damage.
Although the 1993 fire season was well below average in terms of numbers of fires and area burned, strong winds in southern California in late October and November contributed to wildfires burning about 200,000 acres. Three people died and over 1000 homes were destroyed in multiple fires.In terms of length and scope of the fire activity, the 1994 fire season was the most demanding on record to date. Major fires throughout the western United States occurred from the end of May until September. Demand for firefighting resources often exceeded the supply. Thirty-four firefighters lost their lives from one end of the country to the other. Fourteen firefighters lost their lives on a single fire, the Storm King fire in Colorado in early July. Also, for the first time in history $1 billion was spent in fire suppression by all agencies. Seven military battalions were mobilized for firefighting during July and August in the western U.S. A battalion contains approximately 600 people. At the peak of activity in August, more than 25,000 firefighters, 900 engines, 155 helicopters, 54 air tankers, 31 mobile kitchens and 42 shower units were assigned to the fires.
In 1996, record fire activity occurred in Kansas, Oklahoma and Texas with very large areas burned on primarily state and local lands. By mid-August, there were 48 major fires burning in the West; and 90 Incident Management Teams were mobilized to fires. The fire season finally ended in early November. The following year, 1997, exhibited a low level of fire activity nationwide.
The El Niño weather pattern in 1998 produced extremely dry conditions from New Mexico and Texas all the way east to Florida and southern Georgia. Florida and Texas were especially hard hit by wildfires, with many evacuations and losses of homes in Florida.
Intense drought conditions in the western United States in the 2000 fire season contributed towards wildfires burning 120,000 hectares on and near one National Forest in Montana, destroying more than 70 homes and forcing the evacuation of nearly 1000 people. In June, the Hanford fire ripped across 77,700 hectares of southeastern Washington, destroying more than 20 homes and threatening the Hanford Nuclear Reservation. Throughout the nation, wildfires burned about 2.5 million hectares of forests and grasslands. More than 29,000 firefighters attacked the fires with the assistance of 1200 fire engines, 240 helicopters and 50 air tankers. Montana, Idaho and Oregon were declared national disaster areas. The National Guard, Army and Marines were called to action, as were firefighting personnel from Australia, Canada, Mexico and New Zealand.
About 80,000 wildfires occurred in the country and most were controlled at small size by aggressive initial attack efforts. As is usually the case, about 2 percent of the wildfires caused over 90 percent of the area burned. The firefighting efforts cost the United States nearly $1 billion, but it was the onset of September rains that quelled the firestorms. It took appreciable rainfall towards the end of the fire season to overcome the effects of record heat and drought in the western United States in 2000 (Fig. 1).
Figure 1. Record heat and drought made 2000 one of the worst wildfire seasons in the West in 50 years.
In May 2000, the National Park Service in New Mexico ignited a prescribed fire. The fire eventually was called a wildfire and three days later suppression actions contributed to the fire spreading out of the project area into the town of Los Alamos. The fire in Los Alamos destroyed more than 200 homes.
Fire management organization
All Federal and most State wildland fire organizations operate under the National Interagency Incident Management System (NIIMS), which consists of five major subsystems providing for an integrated response to wildfires and other emergencies. The five subsystems include:
Incident Command System for the on-site management of any emergency.
Training (development and delivery of courses in support of wildfires and prescribed fires).
Qualification and Certification (national standards that include training, experience and physical fitness requirements for all wildland fire agencies).
Publications management (development and control of publications, suppliers and distribution of fire-related materials).
The National Interagency Fire Center in Boise, Idaho, coordinates wildfire response activities for all five national resource management agencies; and assists the State fire services as well. In addition, the National Weather Service issues two fire-weather forecasts daily during the fire season to all agencies and prepares spot weather forecasts on request for prescribed fires.
The fire management organization is backed by a strong and diversified fire research program in the United States. Fire research is conducted at two fire research laboratories in California and Montana and at other locations throughout the country. Long duration fire research programs have been instrumental in providing fire managers with fire behavior models, fire effects information, a fire danger rating system, fire retardant information, smoke management protocols and numerous other advances. Technology Development Centers in California and Montana have provided essential support in terms of physical fitness standards, personal protective equipment and firefighting equipment specifications.
Use of prescribed fire to achieve resource management objectives
Prescribed fire, the intentional ignition of grass, shrub, or forest fuels for specific purposes according to predetermined conditions, is a recognized land management practice. Objectives of such burning vary: to reduce fire hazards after logging, expose mineral soil for seedbeds, regulate insects and diseases, perpetuate natural ecosystems and improve range forage and wildlife habitat.
How widespread is the use of prescribed fire, fires designed to produce beneficial results, in the United States today? A survey (Ward and others 1993) indicated that over five million acres are treated annually by prescribed fire in the United States. Over 70 percent of all prescribed burning, or about 3.5 million acres, was in the Southeast. Purposes for using prescribed fire included hazard reduction, silviculture, wildlife habitat improvement, range improvement, vegetation management, and other reasons. The survey lumped such prescribed burning reasons as watershed management, pest control, disease control, and research in the category called “other”.
Resource management agencies and private timber companies cooperate with State Air Quality Bureaus to prescribe burn in a way that reduces adverse effects on human health and visibility. This survey demonstrates that prescribed burning practices are concentrated in the southeastern states. Also, although 5 million acres burned annually appears to be a large number, people are projecting a much greater need for prescribed fire in the future to maintain, or restore, the health of fire-adapted ecosystems.
For example, the new Federal Fire Policy (USDI/USDA 1995)states that: “Managing for landscape health requires expansion of cooperative interagency prescribed fire programs. Agencies must make a commitment with highly qualified people, from leader to practitioner, and provide funding mechanisms to conduct the program.” Recent fire fatalities have focused attention on the need to reduce hazardous fuel concentrations. Many areas need immediate treatment of live and dead vegetation to prevent large, life-threatening, high-intensity wildfires (Mutch 1994). Fuel treatment alternatives include mechanical, chemical, biological, and manual methods, in addition to the use of fire.
In some areas managed by the National Park Service, USDA Forest Service and Bureau of Land Management, naturally ignited fires may be allowed to burn according to approved prescriptions (Kilgore and Heinselman 1990). Fire management areas have been established in national parks and wildernesses from the Florida Everglades to the Sierra Nevada in California. Visitors are increasingly aware that wildland fires can provide an important environment for the enjoyment of park and wilderness experiences.
Fires are not simply allowed to burn. Their spread is monitored to ensure that they remain in designated areas. Suppression measures, backed by modern fire control technology, are employed to protect human life and property and to contain fires within the management unit.
The following wildfire data were summarized from the computerized records maintained by the National Interagency Fire Center located in Boise, Idaho.
Table 1. WildfireDatabase for the United States, 1990-1999
Note: Total number of fires and total area burned by human or natural causes onFederal, State and Private land.
Public policies affecting wildfires and fire management
Recent tragedies in the West focused attention on the need to reduce hazardous fuel accumulations. In the summer of 1994, 34 firefighters lost their lives. The events of that season created a renewed awareness and concern among federal land management agencies and their constituents about wildfire impacts. Federal agencies conducted a combined review of their fire policies and programs. The result was the enactment of a new interagency federal wildland fire management policy, which provided a common approach to wildland fire among all five federal land management agencies (USDI/USDA 1995). The new policy also called for close cooperation with tribal, state and other jurisdictions. Nine major issues were addressed in the new fire policy:
The challenge of managing wildland fire is increasing in complexity and magnitude. Public and private values are seriously at risk and severe ecological deterioration is possible from catastrophic wildfire. The new Federal wildland fire policies are critical and help to strengthen cooperative relationships:
Firefighter and public safety remains the first priority in wildland fire management. Protection of natural and cultural resources and property are the second priority.
Wildland fire, as a critical natural process, must be reintroduced into the ecosystem, accomplished across agency boundaries and based on the best available science.
Where wildland fire cannot be safely reintroduced because of hazardous fuel accumulations, pretreatment must be considered, particularly in the wildland/urban interface.
Wildland fire management decisions and resource management decisions are connected and based on approved plans. Agencies must have the ability to choose from the full spectrum of actions–from prompt suppression to allowing fire to have an ecological function.
All aspects of wildland fire management will involve all partners and have compatible programs, activities and processes.
The role of federal agencies in the wildland/urban interface includes firefighting, hazard fuel reduction, cooperative prevention and education and technical assistance. Ultimately, the primary responsibility rests at the State and local levels.
Structural fire protection in the wildland/urban interface is the responsibility of tribal, state and local governments.
Federal agencies must better educate internal and external audiences about how and why we use and manage wildland fire.
Sustainable land use practices used to reduce wildfire hazards and wildfire risks
Numerous ecosystem indicators from the Southeast to the West are highlighting alarming examples of declining forest health. Attempted fire exclusion practices, prolonged drought and epidemic levels of insects and diseases have coincided to increase wildland fuels, produce extensive forest mortality and cause major changes in forest density and species composition.
Quigley and Cole (1997) reported that fire severity and frequency in the Columbia River Basin have changed across the landscape. Before the settlement of America by Europeans, most fires in the Basin at low to mid elevations were low-intensity fires. Forest and rangelands benefited from these frequent surface fires, which thinned vegetation and favored growth of fire-tolerant trees. In recent times, the area in the Columbia Basin with high intensity, stand replacement fire regimes has more than doubled. This poses a significant threat to ecological integrity, water quality, species recovery and homes in wildland areas.
Gray (1992) called attention to a forest health emergency in parts of the western United States where trees have been killed across a large area in eastern Oregon and Washington. He indicated that similar problems extend over a much larger area south into Utah, Nevada and California and east into Idaho. Denser stands and unnatural fuel accumulations are also causing high-intensity crown fires in Montana, Colorado, Arizona, New Mexico and Nebraska. Historically fires in these long-needled pine forests were more frequent low-intensity surface fires.
Since the 1980s, large wildfires in dead and dying western forests have accelerated the rate of forest mortality, threatening people, property and natural resources (Mutch 1994).
The solution to this problem lies in managing these fire-dependent forests in a more sustainable manner, recognizing that fire is an important ecosystem process vital to forest health (Mutch 1993). The management strategy begins with thinning and harvesting the dense understory of fir; and retaining old growth ponderosa pine, larch and Douglas-fir in the overstory as a seed source. Where large quantities of standing dead trees are present, salvage logging is encouraged to remove large accumulations of fuel. Prescribed fire is carried out on a large scale to reduce the fuel hazard, recycle nutrients and stimulate the regeneration and growth of fire-adapted vegetation. This strategy reduces the density of fir in the stands and abates the future insect infestations and large-scale wildfires. Over the long term, silvicultural partial-cutting and underburning favour retention of more open stands that have a lesser fire hazard.
The U.S. Government Accounting Office (1999) recommended that the Secretary of Agriculture direct the Chief of the Forest Service to develop, and formally communicate to Congress, a cohesive strategy for reducing and maintaining accumulated fuels on national forests at acceptable levels.
Community involvement in fire management activities
The problems of living in a fire environment are no longer unique to southern California, as was thought when these wildland/urban interface fires gained national attention in the 1950s and 1960s. In recent years wildland/urban fire disasters have occurred from coast to coast. As more people move out of cities and into wildlands, these tragedies will recur. Following the recent disastrous fires in several states, recommendations for mitigating the impact of fires in the wildland/urban interface have been developed. The combined efforts of fire protection services, legislators, planners, developers and homeowners will be required to prevent the tragic loss of lives and homes in the wildlands. In other words, community involvement by residents in conducting fire safe measures around their homes is absolutely essential in community protection.
The homeowner has the ultimate responsibility to take the necessary measures to ensure that a home can survive a wildfire. If the proper precautions are taken, a house can survive a wildfire even when the fire services are not able to respond. However, to this day a large number of homeowners throughout the country have not responded in fireproofing property well in advance of the inevitable fires.
Recommendations to reduce the loss of life and property in the wildland/urban interface will be useless unless all stakeholders implement them at the grassroots level. An excellent example of a community-based program is one implemented at Incline Village and Crystal Bay in the Lake Tahoe basin. The objective of this program was to reduce the potential for natural resource, property and human life losses due to wildfire by empowering the residents with the knowledge to address the hazard. The three major components of this defensible-space program included neighborhood leaders, creation of survivable space and agency coordination. The key to protecting life and property in the wildland/urban interface is the property owners’ realization that they have a serious problem and that their actions embody a significant part of the solution. In the Incline Village/Crystal Bay Plan, neighborhood leaders are trained in survivable-space techniques. They are expected to teach these techniques to their neighbors and to coordinate neighborhood efforts. Such concerted community action will minimize the threats from fires in the interface.
It is also wise to have sensible land development practices since tragedies arise not only from ignorance of fuels and fire behavior, but also from greater concern for the aesthetics of a homesite than for fire safety. Several aspects of development detract from fire safety in the wildland/urban interface:
Lack of access to adequate water sources.
Firewood stacked next to houses.
Slash (that is, branches, stumps, logs, and other vegetative residues) piled on homesites or along access roads.
Structures built on slopes with unenclosed stilt foundations.
Trees and shrubs growing next to structures, under eaves and among stilt foundations.
Roads that are steep, narrow, winding, unmapped, unsigned, unnamed and bordered by slash or dense vegetation that make them impossible to drive on during a fire.
Subdivisions on sites without two or more access roads for simultaneous ingress and egress.
Roads and bridges without the grade, design and width to permit simultaneous evacuation by residents and access by firefighters, emergency medical personnel and equipment.
Excessive slopes, heavy fuels, structures built in box canyons and other hazardous situations.
Living fuels that have not been modified by thinning, landscaping, or other methods to reduce vegetation and litter that contribute to fire intensity.
Homes constructed with flammable building materials (wooden shakes, shingles).
Resource management agencies, regulatory agencies and society have failed to implement programs in the past to sustain the health of fire-adapted ecosystems to benefit people, property and natural resources. Today, however, many decades of research results have provided the basis for managing ecosystems more in harmony with disturbance factors to foster the health, resilience and productivity of wildland ecosystems. The principles of ecosystem management can guide society and managers in developing strategies to achieve a range of desired future conditions that will sustain or restore ecosystem health. It has taken 6 or 7 decades to produce today’s decline in many forested ecosystems in the United States. It will take an equally long time to reverse this trend. Fortunately, many resource management agencies are commencing ecosystem restoration programs at this time.
Note: This paper is the official contribution to the FAO Global Forest Fire Assessment1990-2000.
Robert W. Mutch
Fire Management Applications
USDA Forest Service
Intermountain Fire Sciences Laboratory
PO Box 8089
USA – Missoula, MT 59807
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