WILDFIRE DISASTERS

Definition

Wildfire is defined as an "unplanned fire burning in natural (wildland) areas such as forests, shrub lands, grasslands, or prairies" and peatland. This contrasts with the practice of planned or prescribed fires. During the past 60 years forest fires accounted for two-thirds (67%) of wildfires and were 2.5 times more common than land fires (27%).

Speed of Onset and Duration

Depending on environmental conditions, wildfires can start within hours and spread rapidly within a day. Depending on the location and resources available, it is possible to contain most wildfires within one week in the United States. However, wildfires can also burn for weeks or months. The largest wildfire in world history also had the most prolonged duration. One single fire in 1950 burned approximately three million acres (1.2 million hectares) of forest and lasted for five months.

Consequences

Wildfires often pose a characteristic logistical challenge related to the wilderness in which they occur. Wildlands are areas where development is essentially nonexistent (except for roads, railroads, power lines, and similar transportation facilities).

Because of the relative isolation and lack of infrastructure in wildlands, wildfires that result in evacuations do not typically result in the long-term displacement of large populations. During the past 60 years 1% of persons affected by wildfires were also reported homeless. However, some populations and locations are at higher risk of being trapped by wildfire. Forest fires occurring near highly populated cities are also of concern, since they add to the impacts of high urban pollution levels and can also affect navigation and transportation.

Scale

During the past 60 years there were 445 wildfire disasters reported worldwide that caused an average of 15 deaths per incident.

The geographical scale of the individual fire is often dwarfed by the extent of air pollution created by wildfire smoke. The adverse effect on air quality can have an enormous impact, extending throughout an entire world region. The term South Asia haze has been coined to describe the fire-related transboundary air pollution that recurrently results from burning biomass. First reported in the 1970s, this phenomenon has affected Indonesia, Malaysia, Singapore, Thailand, and Brunei. It has also been reported to affect the Philippines, Thailand, Vietnam, Cambodia, and countries outside the region.

Severity

A widely used measure of fire intensity is known as fireline intensity, which is the rate of heat transfer per length of fire line. This measure represents the radiant energy release in the flaming front.

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Excerpted from Keim, M. Emergency Health: Principles and Practice. American Public Health Association Press, Washington, DC. May 2023. p. 74-75.