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While fire is an essential ecological process in maintaining functional ecosystems, it also produces combustion products that are harmful to human health and welfare. Probably the most common air quality issues facing wildland and prescribed fire managers are those related to public complaints about nuisance smoke. Complaints may be about the odor or soiling effects of smoke, poor visibility, and impaired ability to breathe or other health-related effects. Small particulate matter in smoke can cause acute health effects, such as respiratory and immune problems. These same particles are also largely responsible for visibility reduction in the form of regional haze. Perhaps the most immediate need for an effective smoke management program is related to smoke drifting across roadways and restricting motorist visibility. Each year, people are killed on the nation’s highways because of dust storms, smoke and fog. These and other adverse impacts of wildland and prescribed fire smoke are discussed in the following sections:
Because these and other consequences of smoke, there has been a call for increasingly effective smoke management programs to reduce these possible risks of wildland and prescribed fire to public health, welfare, and safety. Fire managers have a responsibility to try to prevent or resolve these issues through smoke management plans that recognize the importance of proper selection of management and burning techniques and burn scheduling based on meteorological conditions. In addition, community public relations and education coupled with pre-burn notification can greatly improve public acceptance of fire management programs.
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In 1996, the Environmental Protection Agency (EPA) conducted an extensive review of the science relating human health effects to particulate matter (PM), the principal pollutant of concern from fires (EPA 1996). The review found that (1) epidemiological studies suggest a variety of health effects at concentrations found in several U.S. cities and (2) ambient particles of greatest concern to health were those smaller than 10 micrometers in diameter. Results of efforts to trace the physiological and pathological responses of the body to PM are unclear, and demonstration of possible mechanisms linking ambient PM to mortality and morbidity are derived from hypotheses in animal and human studies. It is known, however, that PM produces physiological and pathological effects by a variety of mechanisms, including:
Recent information also suggests that several sub-groups within the population are more sensitive to PM than others. Children are more likely to have decreased pulmonary function, while increased mortality has been reported in the elderly and in individuals with cardiopulmonary disease. Asthmatics are especially susceptible to PM exposure. In addition, coarse (2.5 to 10µm) particles from road dust or windblown soil were found to have less toxicity than fine particles (less than 2.5µm) that include acid aerosols, diesel emissions, smoke from fires, and potentially carcinogenic PAH compounds.
Wildland firefighters and fire managers have long been aware that smoke exposure occurs during their work (Reinhardt and Ottmar 1997; Sharkey 1997). Although the long-term health effects from occupational smoke exposure remain unknown, the evidence to date suggests that brief, intense smoke exposures can easily exceed short-term exposure limits in peak exposure situations such as direct attack and holding firelines downwind of an active wildfire or prescribed burn. Shift-average exposure only occasionally exceeds recommended instantaneous exposure limits set by the American Conference of Governmental Industrial Hygienists (ACGIH), and rarely do they exceed Occupational Safety and Health Administration (OSHA) time weighted average (TWA) limits (Reinhardt and Ottmar 2000; Reinhardt and others 2000). Overexposure increases to 10 percent of the time if the exposure limits are adjusted for unique aspects of the fire management workplace; these aspects include hard breathing, extended hours, and high elevations, all factors which intensify the effects of many of the health hazards of smoke (Betchley and others 1995; Materna and others 1992; Reinhardt and Ottmar 2000; Reinhardt and others 2000). It could be argued that few firefighters spend a working lifetime in the fire profession, and thus they should be exempt from occupational standards that are set to protect workers over their careers. But this argument is irrelevant for irritants and fast-acting health effects such as eye and respiratory irritation, headache, nausea, and angina. An exposure standard specifically for wildland firefighters and appropriate respiratory protection may need to be developed (Reinhardt and Ottmar 2000).
In spite of the studies that have been done, major data gaps remain:
Although data gaps remain, enough information has been gathered to chart a course to alleviate many of the overexposures. Respiratory protection is available for irritants such as aldehydes and particulate matter but not for carbon monoxide. Respirators can be heavy, hot, and impede the speed of work, but some new models are light, simple and could be worn only when needed (Beason and others 1996; Rothwell and Sharkey 1995). The entire costly process of medical evaluations, fitness testing, maintenance, and training must be employed if respirators are to be used. But there are immediate benefits to reducing respiratory irritant exposure. Small electrochemical dosimeters can pro- vide instant warnings about carbon monoxide levels in a smoky situation, and fire crew members equipped with respirators and carbon monoxide monitors have all the protection necessary to stay and accomplish objectives safely and withdraw when the carbon monoxide levels become the limiting factors (Reinhardt and others 1999). In the future, a respirator for use during wildland fires may be developed that offers warning and protection against carbon monoxide as well. Although some work has been done in this area, we need more significant development. Smoke exposure is a hazard only a small portion of the time and is manageable because the situation where it occurs can be predicted. A long-term program to manage smoke exposure at wildland fires could include (1) hazard awareness training, (2) implementation of practices to reduce smoke exposure such as rotating crews and providing clean air sites, (3) routine carbon monoxide monitoring with electronic dosimeters, (4) improved recordkeeping on accident reports to include separation of smoke related illness among fireline workers and fire camp personnel, and (5) improved nutritional and health habits. Fire management practices such as crew rotation, awareness training, and carbon monoxide monitoring can mitigate the hazard and allow firefighters to focus on the job of fire management, lessening the distraction, discomfort, and health impacts of smoke exposure (Reinhardt and Ottmar 2000).
A number of wildland fire health effect research issues flow from the EPA staff report (Clean Air Scientific Advisory Committee 1995) and occupational health exposure studies.
Research into the health effects of particulate matter is largely based on epidemiological studies conducted over long periods in urban centers with high hospital admittance or large air quality databases, or both. Consequently, inadequate information is available that relates short-term, acute smoke exposure (such as would be experienced by a visitor to a National Park or to a community near a wildfire) to human health effects. As a result, little or no specific guidance is available to wildland fire managers, air quality regulators, or public health officials who need to responsibly judge the public health risks of exposure to extremely high smoke concentrations. This gap in knowledge was clearly evident during the 1988 Yellowstone fires and later wildfire events when quick decisions had to be made on how best to protect public health in communities near major wildfires (WESTAR 1995). The best available guidelines are those published by EPA (1999) for assessing the risk to health from air pollution (table 8-1). These guidelines may or may not reflect the specific hazards of pollutants from fires, which will have a different chemical composition.
The long-term health effects of smoke exposure to wildland firefighters are unknown in spite of anecdotal evidence that indicates the possibility of a greater incidence of cardiopulmonary disease and death than in the general population. Although carbon monoxide monitoring and respiratory protection can mitigate the hazard, personal protection equipment is still needed that allows firefighters to work effectively without discomfort or distraction (Reinhardt 2000).
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The deposition of smoke particles on the surface of buildings, automobiles, clothing, and other objects reduces aesthetic appeal and damages a variety of objects and building structures (Baedecker and others 1991). Studies of the effect of aerodynamic particle size on soiling have concluded that coarse particles (2.5 to 10µm) initially contribute more to soiling of both horizontal and vertical surfaces than do fine particles (less than 2.5µm), but that coarse particles are more easily removed by rainfall (Haynie and Lemmons 1990). Smoke from fires is largely within the fine mode, although ash fallout in the near vicinity of a fire is often also a concern. Smoke may also discolor artificial surfaces such as building bricks or stucco, requiring cleaning or repainting. Increasing the frequency of cleaning, washing, or repainting soiled surfaces becomes an economic burden and can reduce the life usefulness of the soiled material (Maler and Wyzga 1976).
Soiling from smoke also changes the reflectance of opaque materials and reduces light transmission through windows and other transparent materials (Beloin and Haynie 1975).
When fine smoke particles (less than 2.5µm) infiltrate indoor environments, soiling of fabrics, painted interior walls, and works of art may occur. Curtains may require more frequent washing because of soiling or may deteriorate along folds in the fabric after being weakened by particle exposure (Yocom and Upham 1977). As in the case of corrosion damage from acidified particles, these same particles accelerate damage to painted surfaces (Cowling and Roberts 1954). Studies of the soiling of works of art at a museum in southern California concluded that a significant fraction of the dark-colored fine mode elemental carbon and soil dust originated from outdoor sources (Ligocki and others 1993). Smoke from fires is one source of elemental carbon. For more information see Soiling-related Economic Costs.
Nuisance smoke is the amount of smoke in the ambient air that interferes with a right or privilege common to members of the public, including the use or enjoyment of public or private resources (EPA 1990). The abatement of nuisance smoke is one of the most important objectives of successful smoke management (Shelby and Speaker 1990). Public complaints about nuisance smoke are linked to loss of visibility, odors, and ash fallout that soils buildings, cars, laundry, and other objects. Acrolein (and possibly formaldehyde) in smoke at distances of 1 mile from the fireline are likely to cause eye and nose irritation, exacerbating public nuisance conditions (Sandberg and Dost 1990).
Perhaps the most significant nuisance effect of smoke from fire is local visibility reduction in areas impacted by the plume. While visibility loss within Class I areas is subject to regulation under the Clean Air Act, smoke plume-related visibility degradation in urban and rural communities is not. Nuisance is usually regulated under State and local laws and is frequently based on public complaint or, when highway safety is compromised, the risk of litigation (Eshee 1995). The courts have also ruled that the taking of private property by interfering with its use and enjoyment caused by smoke (and without just compensation) is in violation of Federal Constitutional provisions under the Fifth Amendment. The trespass of smoke may diminish the value of the property, resulting in losses to the owner (Iowa Supreme Court 1998).
Because the public links visibility loss with concerns about the health implications of breathing smoke, smoke management programs have been under increasing pressure to minimize emissions and reduce smoke impacts to the greatest degree possible (Core 1989). Visibility reduction is used as a measure of smoke intrusions in several smoke management plans. The State of Oregon program operational guidance defines a "moderately" intense intrusion as a reduction of from 4.6 to 11.4 miles from a background visibility of more than 50 miles (Oregon Department of Forestry 1992). The State of Washington smoke intrusion reporting system uses a "slightly visible," "noticeable impact on visibility" or "excessive impact on visibility" to define light, medium, and heavy intrusions (Washington Department of Natural Resources 1993). The State of New Mexico program requires that visibility impacts of smoke be considered in development of the units burn prescription (New Mexico Environmental Improvement Board 1995).
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Every year there are over 280 million visitors to our nation’s wilderness areas and national parks. Congress has set these special places aside for the enjoyment of all that seek spectacular and inspiring vistas. Unfortunately, many visitors are not able to see the beautiful scenery they expect. During much of the year, a veil of haze often blurs their view. The haze is caused by many sources of both natural and manmade air pollution sources, including wildland fire.
This section describes measures of scenic visibility, the properties of the atmosphere and how these properties are affected by smoke from wildland fires, natural and current visibility conditions, as well as sources that contribute to visibility degradation. This is an important issue to wildland fire practitioners because smoke is of increasing interest to air regulators responsible for solving regional haze problems.
Visibility is most often thought of in terms of visual range or the furthest distance a person can see a landscape feature. However, visibility is more than how far one can see; it also encompasses how well scenic landscape features can be seen and appreciated. Changes in visual range are not proportional to human perception. For example, a five-mile change in visual range can result in a scene change that is either imperceptible or very obvious depending on the baseline visibility conditions. Therefore, a more meaningful visibility index has been adopted. The scale of this index, expressed in deciviews (dv) is linear with respect to perceived visual changes over its entire range, analogous to the decibel scale for sound. A one-deciview change represents a change in scenic quality that would be noticeable to most people regardless of the initial visibility conditions. A deciview of zero is equivalent to clear air while deciviews greater than zero depict proportionally increased visibility impairment (IMPROVE 1994). The more deciviews measured, the greater the impairment, which limits the distance you can see. Finally, extinction in inverse megameters (Mm-1) is proportional to the amount of light lost as it travels through a million meters of atmosphere and is most useful for relating visibility directly to particulate concentrations. Table 3.2.1 compares each of these three forms of measurement (Malm 2000).
An observer sees an image of a distant object because light is reflected from the object along the sight path to the observer’s eye. Any of this image-forming light that is removed from the sight path by scattering or light absorption reduces the image-forming information and thereby diminishes the clarity of the landscape feature. Ambient light is also scattered into the sight path, competing with the image-forming light to reduce the clarity of the object of interest. This “competition” between image-forming light and scattered light is commonly experienced while driving in a snowstorm at night with the car headlights on.
In addition, relative humidity also indirectly affects visibility. Although relative humidity does not by itself cause visibility to be degraded, some particles, especially sulfates, accumulate water from the atmosphere and grow to a size where they are particularly efficient at scattering light. Poor visibility in the eastern states during the summer months is a result of the combination of high sulfate concentrations and high relative humidity.
The sum of scattering and absorption is referred to as atmospheric light extinction. Particles that are responsible for scattering are categorized as primary and secondary where primary sources include smoke from wildland fires and windblown dust. Other sources of secondary particles include sulfate and nitrate particles formed in the atmosphere. The closer the particle size is to the wavelength of light, the more effective the particle is in scattering light. As a result, relatively large particles of windblown dust are far less efficient in scattering light per unit mass than are the fine particles found in smoke from wildland fires. Finally, an important component of smoke from wildland fires is elemental carbon (also known as soot), which is highly effective in absorbing light within the sight path. This combination of light absorption by elemental carbon and light scattering caused by the very small particles that make up wildland fire smoke explains why emissions from wildland fire play such an important role in visibility impairment.
Some light extinction occurs naturally due to scattering caused by the molecules that make up the atmosphere. This is called Rayleigh scattering and is the reason why the sky appears blue. But even without the influence of human-caused air pollution, visibility would not always reach the approximately 240-mile limit defined by Rayleigh scattering. Naturally occurring particles, such as windblown dust, smoke from natural fires, volcanic activity, and biogenic emissions (e.g. pollen and gaseous hydrocarbon) also contribute to visibility impairment although the concentrations and sources of some of these particles remain a point of investigation.
Average natural visibility in the eastern U.S. is estimated to be about 60-80 miles (8-11 dv), whereas in the western U.S. it is about 110-115 miles (4.5-5 dv) (Malm 2000). Lower natural visibility in the eastern U.S. is due to higher average humidity. Humidity causes fine particles to stick together, grow in size, and become more efficient at scattering light. Under natural conditions, carbon-based particles are responsible for most of the non-Rayleigh particle associated visibility reduction, with all other particle species contributing significantly less. Scattering from naturally occurring sulfate particles from volcanic sulfur dioxide emissions and oceanic sources of primary sulfate particles are estimated to account for 9-12% of the impairment in the East and 5% in the West (NPS 1997). It is expected that coastlines and highly vegetated areas may be lower than these averages, while some elevated areas (mountains) could exceed these background estimates.
Currently, average visual range in the eastern U.S. is about 15-30 miles, or about one-third of the estimated natural background for the East. In the West, visual range currently averages about 60-90 miles, or about one-half of the estimated natural background for the West. Current annual visual range conditions expressed in miles are shown in figure 3.2.2. Notice how much more impaired visibility is in the East versus the West.
In the East, 60-70% of the visibility impairment is attributed to sulfates. Sulfate particles form from sulfur dioxide gas, most of which is released from coal-burning power plants and other industrial sources such as smelters, industrial boilers, and oil refineries. Carbon-based particles contribute about 20% of the impairment in the East. Sources of organic carbon particles include vehicle exhaust, vehicle refueling, solvent evaporation, food cooking, and fires.
Elemental carbon particles (or light absorbing carbon) are emitted by virtually all combustion activities, but are especially prevalent in diesel exhaust and smoke from wood burning.
In the West, sulfates contribute less than 30% (Oregon, Idaho and Nevada) to 40-50% (Arizona, New Mexico and Southwest Texas) of light extinction. Carbon particles in the West are a greater percentage of the extinction budget ranging from 50% or greater in the Northwest to 30-40% in the other western regions. The higher percentages of the extinction budget associated with carbon particles in the West appear to be from smoke emitted by wildland and agricultural fires (NPS 1994).
In summary, the physics of light extinction in the atmosphere coupled with the chemical composition and physical size distribution of particles in wildland fire smoke combine to make fire (especially in the West) an important contributor to visibility impairment. Wildland fire managers responsible for the protection of the scenic vistas of this nation’s wilderness areas and national parks have a difficult challenge in balancing the need to protect visibility with the need to use fire for other resource management goals.
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The economic consequences of smoke are principally in the areas of soiling-related losses and costs related to reduced visibility.
Economic costs associated with materials damage and soiling caused by airborne particles include reduction in the useful life of the damaged materials and the decreased utility of the object. Losses caused by the need for more frequent maintenance and cleaning are also significant. Amenity losses occur when the increased cleaning or repair of materials results in inconvenience or delays, many of which are difficult to quantify (Maler and Wyzga 1976).
Within the United States, however, the soiling of buildings constitutes the largest category of surface areas at risk to pollution damage (Lipfert and Daum 1992). Soiling on painted surfaces on residential buildings, resulting in a need to repaint exterior walls, has caused damage approaching $1 billion per year (Haynie and others 1990).
Willingness-to-pay estimates developed using the contingent valuation method found that households were willing to pay $2.70 per µg/m3 charge in particle pollution to avoid soiling effects (McClelland and others 1991). No estimates are available for costs specifically associated with smoke from fires.
The importance of clean, clear air within the wildlands and National Parks of this nation is hard to overemphasize. People go to these special places to enjoy scenery, the color of the landscapes, and clarity of the vistas. At Grand Canyon, 82 percent of 638 respondents rated "clean, clear air" as very important or extremely important to their recreational experience (Ross 1988). Three National Park Service (NPS) studies determined that air quality conditions affect the amount of time and money visitors are willing to spend at NPS units (Brookshire and others 1976; MacFarland and others 1983; Schulze and others 1983). These studies found estimated onsite use values for the prevention or elimination of plumes that ranged from about $3 to $6 (1989 dollars) per day per visitor party at the park. Based on these results, the implied preservation value for preventing a visible plume most days (the exact frequency was not specified) at the Grand Canyon was estimated at about $5.7 billion each year when applied to the total U.S. population (EPA 1996). Other investigators have suggested that these estimates are overstated by a factor of 2 or 3 (Chestnut and Rowe 1990).
In the studies noted above, park visitors generally responded that they would be willing to spend more time and money if visibility conditions were better and, conversely, less if visibility conditions were worse (Ross 1988). The average amount of time visitors were willing to spend traveling to a vista for every unit change in visibility (.01 km extinction coefficient) was between 15 minutes and 4 hours. These results provide evidence that changes in visual air quality can be expected to affect visitor enjoyment and satisfaction with park visits.
Even given the limitations and uncertainties of contingent valuation surveys, economic values related to visibility degradation are clearly likely to be substantial.
Perceived visual air quality (PVAQ) has been used as a measure of the publics acceptance of haze conditions (Middleton and others 1983). Subjects were asked to judge the visual air quality in several photos depicting vistas under different haze conditions using a scale of 1 to 10, 1 being the worst and 10 being the best. These 1 to 10 scales reflect peoples perceptions and judgments concerning visibility conditions. By matching particulate air quality conditions that occurred at the time of the photographs, researchers have been able to develop a relationship between PVAQ and particulate matter concentrations (Middleton and others 1985). Even small increases in particulate concentrations in the atmosphere result in dramatic decreases in PVAQ. Because of the light scattering efficiency of smoke, this relationship is especially applicable to fire emissions.
"National parks and wilderness areas are among our nations greatest treasures. Ranging from inviting coastal beaches and beautiful shorelines to colorful deserts and dramatic canyons to towering mountains and spectacular glaciers, these regions inspire us as individuals and as a nation" (NRC 1993). With these words, the National Research Council (NRC) noted the importance of preserving the scenic vistas of the nation. Congress, in recognition of the scenic values of the nation, adopted the Clean Air Act Amendments of 1977, which established a national visibility protection program. The GCVTC was later established in the 1990 amendments to the act to address visibility impairment issues relevant to the region surrounding Grand Canyon National Park. Following 4 years of study, the GCVTC concluded that smoke from wildland fires is likely to have the single greatest impact on visibility in Class I areas of the Colorado Plateau through the year 2040 (GCVTC 1996c). While difficult to quantify, there is consensus that visibility loss associated with smoke from wildland fire and other sources has important cultural consequences on the nation.
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Smoke can cause highway safety problems when it impedes a drivers ability to see the roadway and can result in loss of life and in property damage at smoke levels that are far below NAAQS. This section focuses on highway safety issues in the Southeastern United States because this is where the foremost forestry-related air quality problem has been in the past. We also describe tools being developed to aid the land manager in avoiding highway safety problems.
Although smoke at times can become a problem anywhere in the country, it is in the Southern States, from Virginia to Texas and from the Ohio River southward, where highway safety is most at risk from prescribed fire smoke, principally because of the amount of burning done in the South and the proximity of wildlands to population centers. Roughly 4 million acres of Southern forests are treated with prescribed fire each year (Wade and Lunsford 1988). This area is by far the largest acreage subjected to prescribed fire in the country. Prescribed fire treatment intervals, especially in Southern pine (in an area extending roughly from Virginia to Texas), is every 3 to 5 years. These forests are intermixed with homes, small towns, and scattered villages within an enormous wildland/urban interface. During the daytime, smoke becomes a problem when it drifts into these areas of human habitation. At night, smoke can become entrapped near the ground and, in combination with fog, creates visibility reductions that cause roadway accidents. The potential exists for frequent and severe smoke intrusions onto the public roads and highways from both prescribed and wildland fires.
Smoke and smoke/fog obstructions of visibility on Southeastern United States highways cause numerous accidents with loss of life and personal injuries every year. Several attempts to compile records of smoke-implicated highway accidents have been made. For the 10 years from 1979 through 1988, Mobley (1989) reported 28 fatalities, over 60 serious injuries, numerous minor injuries, and millions of dollars in lawsuits. During 2000, smoke from wildfires drifting across Interstate 10 caused at least 10 fatalities, five in Florida and five in Mississippi.
As the population growth in the South continues, more people will likely be adversely impacted by smoke on the highways. Unless methods are found to adequately protect public safety on the highways, there exists the prospect that increasingly restrictive regulations will curtail the use of prescribed fire or that fire as a management tool may be altogether prohibited.
Several approaches are being taken to reduce the uncertainty of predicting smoke movement over roadways:
High-resolution weather prediction models promise to provide increased accuracy in predictions of wind speeds and directions and mixing heights at time and spatial scales useful for land managers. The Florida Division of Forestry (FDOF) is a leader in the use of high resolution modeling for forestry applications in the South (Brenner and others 2001). Because much of Florida is located within 20 miles of a coastline, accurate predictions of sea/land breezes and associated changes in temperature, wind direction, atmospheric stability, and mixing height are critical to the success of the FDOF. High-resolution modeling consortia are also being established by the USDA Forest Service to serve clients with interests as diverse as fire weather, air quality, ecology, and meteorology. These centers involve scientists in development of new products and in technology transfer to bring the products to consortia members.
Several smoke models are in operation or are being developed to predict smoke movement over Southern landscapes. VSMOKE (Lavdas 1996), a Gaussian plume model that assumes level terrain and unchanging winds, predicts smoke movement and concentration during daytime. VSMOKE has been made part of the FDOF fire and smoke prediction system. It is a screening model that aids land managers in assessing where smoke might impact sensitive targets as part of planning for prescribed burns. PB-Piedmont (Achtemeier 2001) is a wind and smoke model designed to simulate smoke movement near the ground under entrapment conditions at night. The smoke plume is simulated as an ensemble of particles that are transported by local winds over complex terrain characteristic of the shallow (30 to 50 m) interlocking ridge/valley systems typical of the Piedmont of the South. Two sister models are planned -- one that will simulate near-ground smoke movement near coastal areas influenced by sea/land circulations, and the other for the Appalachian Mountains.
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Globally, fires are a significant contributor of carbon dioxide and other greenhouse gases in the atmosphere. Fires account for approximately one-fifth of the total global emissions of carbon dioxide (Levine and Cofer 2000; Schimel 1995). Andreae and Merlet (2001) calculate that 5,130 Tg per year of biomass is consumed in fires, emitting 8,200 Tg per year of carbon dioxide, 413 Tg per year of carbon monoxide, and 19.4 Tg per year of methane. The accuracy of these global estimates is thought to be within plus or minus 50 percent, with the bulk of the error resulting from inaccuracies in the estimates of the area burned and the mass of fuel consumed.
Fires in temperate ecosystems are minor contributors compared to the worlds savannas, boreal forests, and tropical forests. More than 60 percent of the totals listed in the previous paragraph are released from savannas and grasslands, and another 25 percent from tropical forests. Burning in tropical Africa is dominated by savanna fires; in tropical Asia, by forest fires; and in tropical South America, about equally represented by savannas and tropical forests (Hao and Liu 1994). Lavoué and others (2000) detail contributions from temperate and boreal fires, demonstrating that about 90 percent of the global boreal fire area is in Russia and Canada. Alaska accounts for only about 4.5 percent of the global boreal forest, but it accounts for at least 10 percent of the emissions from that source, because of the heavier fuel loads in Alaska. Alaska accounts for an average of 41 percent of total U.S. fire emissions, with a huge year-to-year variability. In 1990, 89 percent of U.S. fire emissions were from Alaska fires (see: Smoke from Wildland Fires).
Currently, there is no policy mandate, nor widely accepted methodology for managing fires, for the conservation of terrestrial carbon pools or mitigation of greenhouse gas emissions. However, we may expect carbon accounting and perhaps conservation to become a part of fire and air resource management if and when global agreements are made to address biomass burning and resultant greenhouse gas emissions.
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