Where there’s fire, there’s smoke—a fact that often gets lost amid the more obvious destruction caused by wildfires.
Over the past several years, a rash of wildfire disasters has hit the western part of the United States, most devastatingly with California’s Camp Fire in 2018.
The Camp Fire killed 86 civilians, destroyed more than 18,000 buildings, and caused more than $12 billion in insured losses in Paradise, California and surrounding communities.
During these devastating events, news stories typically focus on the tangible destruction caused directly by wildfires. But during these fires and in their aftermath, smoke emissions are responsible for a significant amount of the damages. In fact, recent evidence suggests that perhaps the largest damages from wildfires are due to the health consequences from smoke emissions. Severe smoke damages will continue to be an issue unless policymakers can facilitate forest management practices, such as prescribed burns, to mitigate the increasing intensity and frequency of wildfire events.
Wildfire smoke is a mélange of water vapor, gases (e.g., carbon dioxide and carbon monoxide), and particulate matter. Particulate matter under 2.5 micrometers in diameter (known as PM 2.5) is of special concern for human health, because it can more easily enter the lungs and bloodstream. Research indicates that exposure to high levels of PM 2.5 can lead to mortality among vulnerable groups such as the elderly; increased health care utilization; increased crime and aggressive behavior; and decreases in cognitive functioning, work hours, and worker productivity.
Wildfire smoke rarely is confined to the immediate area surrounding the wildfire. In the weeks after the start of the Camp Fire in Paradise, California, PM 2.5 levels in the Bay Area rose to more than 250 micrograms per cubic meter. (For comparison, average annual concentrations of PM 2.5 in Beijing are approximately 51 micrograms per cubic meter.) Heat generated by wildfires can push smoke high up into the atmosphere, where the jet stream disperses it over great distances. Depending on how researchers choose to define a smoky day, wildfires cause between 20 and 70 smoky days per year in the most severely affected parts of the United States. These areas may include much of the Midwest—even though few fires begin there.
Costs due to wildfire smoke might be expected to add up, and recent research suggests this is indeed the case. A working paper from researchers at the University of Illinois at Urbana-Champaign suggests that wildfire smoke results in over 1,300 deaths across the United States annually and a 0.5 percent spike in hospital admissions on smoky days. Another paper estimates that US annual wage earnings decrease by about one percent per year due to wildfire smoke, equivalent to $95 billion. Additionally, previous evidence indicates that wildfire smoke can lead to increased infant mortality, along with reduced birthweight, which is associated with a wide range of health and economic outcomes later in life.
This recent research suggests that the costs of wildfire smoke are large. Worse still, they are likely to increase in coming years. The amount of area burned in large fires within the western United States has increased by 1,200 percent due to climate change, longer fire seasons, and hazardous conditions in western forests.
In the short run, individuals and communities reduce health damages due to wildfire smoke by staying indoors, avoiding physical activity when it is smoky outside, and installing air filtration systems in buildings. In the longer run, though, the quality of life in many western states will dramatically suffer if wildfire smoke becomes a permanent feature of late summer. All of this raises a question: What should be done about wildfire smoke?
Unfortunately, the solution is not as simple as, “Put out the fires.”
Historically, mixed-severity fires burned frequently within many western forests. These fires removed vegetation and helped to maintain a heterogeneous landscape with many natural “firebreaks,” where an absence of fuels helped to slow the spread of fire. Beginning in the early twentieth century, the US Forest Service and other land management agencies adopted a zero-tolerance policy toward fire, leading to the accumulation of vegetation within the understory of many western forests. But understory vegetation can carry fire up into the forest canopy, where it burns more intensely, is more difficult and dangerous to manage, and releases more smoke.
Today, the US Forest Service estimates that 65 to 82 million of the agency’s 190 million acres of land are in need of management activities (for example, prescribed burns) to restore historic ecological conditions; remove fuels and reduce wildfire severity; and cut down on damage from insects, disease, and climatic stressors.
The most cost-effective methods of removing fuels and providing ecosystem benefits involve the use of fire under favorable conditions. In a managed wildfire, managers allow the wildfire to burn, whereas in a prescribed burn, fire is intentionally set. Typically, because prescribed fires and managed wildfires are smaller and burn a lower proportion of the landscape’s vegetation, they also release less smoke than fires that are managed under full suppression. These types of management activities are permitted on a limited basis, during times when smoke will not drift into populated areas.
Policymakers need to consider that reducing smoke in the long run may require tolerating some smoke in the short run. Forgoing opportunities for a low-severity, low-smoke fire today may increase the likelihood of higher-severity fires, more intense smoke, and greater damages to human health in years to come. Worse still, when future high-severity fires strike, they may present greater risks to lives and property. Historically, however, it has been difficult for managers to balance these costs and benefits, in part due to the “temporal mismatch” between the costs and benefits of prescribed burns and managed wildfires: the costs of prescribed burns and wildfires are near at hand, while the benefits accrue in the future and are uncertain.
Fortunately, policy changes are making it easier for managers to give greater weight to future benefits. States typically approve prescribed burns under limited circumstances, when smoke will not drift into populated areas; however, requirements for ideal conditions can limit the opportunities to implement prescribed burns. Oregon’s Department of Environmental Quality has recently experimented with relaxing its rules regarding the smoke impacts of prescribed burns, and this development is expected to increase the ability of managers to implement prescribed burns.
In addition, the EPA allows wildfires to be treated as “exceptional events,” a classification that prevents areas from being held accountable for violating EPA air quality standards due to unavoidable wildfire smoke. In some cases, prescribed fires and managed wildfires also can be treated as exceptional events. This rule provides leeway for the use of these management tools, which hopefully will improve future air quality.
Wildfire smoke—now a fact of life during late summer and early fall in many communities—does serious harm to human health throughout the western region of the United States. Unfortunately, mitigating harm from wildfire smoke in the long run may require greater tolerance for light smoke in the short run. Though managers should remain cautious about the effects of prescribed fires and managed wildfires on air quality today, they should also consider the future impacts of their management decisions on air quality.