Wildfires: How They Get Out of Control

An overview of wildfires

In general, environmental disasters are beyond human control. However, the economic, political, and social contexts transform what is an environmental hazard into an environmental disaster.

In the case of wildfires, various human-related factors increase the risk of disaster by generating higher exposure and susceptibility. The impact of wildfires on the environment and human communities is immense. Air pollution, water runoff, destruction of habitat, loss of vegetation and wildlife populations, and permafrost thawing are some of the several environmental effects of wildfires.^[1] For human communities, wildfires can be life-threatening.^[2] Every year, approximately 340,000 deaths are related to respiratory and cardiovascular problems attributed to the harmful smoke from wildfires. In addition, the estimated costs associated with health problems are about USD 87 billion per year.^[3]

Furthermore, the destruction and loss of homes (Figure 1) and belongings, the threat to their own, their loved ones, and neighbours’ safety carries a tremendous burden on the mental health of those affected by the wildfires.^[4]

What are wildfires?

Occurring unplanned, and often caused by human intervention, a wildfire burns in a natural area (e.g., forest, grassland, prairie) and could be caused by accident, negligence, or intentionally.^[5] Less frequently, wildfires can also start from a naturally occurring phenomenon such as lighting, meteor, or volcanic activity.^[6]

Regardless of how they are caused, all wildfires require three key components to ignite and spread, the so-called fire triangle: fuel, heat, and oxygen^[7]. These three components must be present to start the chemical reaction of combustion. The oxygen content in the air will react with the fuel (e.g., dry grass), triggered by a heat source such as a discarded cigarette or hot coals.^[8] The fuel must be heated to its flash point to ignite and start the combustion, which will lead to a subsequent fire. Drought, high temperatures, and abnormally dry conditions throughout the seasons are the main factors contributing to the increase in the frequency and intensity of wildfires. According to the WHO, the effects of climate change are leading to warmer temperatures and drier conditions. This promotes earlier and longer fire seasons.^[9]

Other key factors are the growing urbanization and the deforestation of rural areas, which increase the risk of damages from wildfires.^[10]

Factors contributing to wildfire spread

Dry, hot, and windy conditions are the perfect recipe for the start and spread of a wildfire. The fuels are more prone to ignition in warmer temperatures with low relative humidity, provoking the easier start of fires.^[11] The Strongs winds have a double effect, first as an enormous supply of oxygen, and second, as a carrying agent for ashes and sparks to the surrounding areas of the flaming front.^[12]

Not only does the weather determine how the wildfire can spread, but the topography (e.g., slope, aspect, elevation) can also influence the behaviour of a wildfire. The topography of an affected zone affects fuel moisture and local wind patterns.^[13] Fires tend to follow the wind direction, and combined with the rising heat and smoke, the fuel is drier up the slope.^[14] This causes the spread of wildfires commonly uphill side, as can be observed in Figure 2.

The type and amount of fuel is also determinant for the spread of wildfires. There are several flammable plant materials, particularly, fallen pine needles, dead leaves and grasses, shrubs, and trees. The accumulation of these plant materials, combined with the weather conditions makes the wildfires burn in a stronger, larger, longer, and quicker manner.^[15]

Large amounts of accumulated highly flammable plant material can be associated with fire suppression activities carried out by different governmental and environmental agencies.^[16] Recent evidence suggests that aggressive suppression policies lead to an increment in the flammability of forests near human settlements.^[17] This is known as the fire paradox: the more we try to control wildfires, the more flammable material accumulates, which increases the risk of future wildfires.^[18]

Fire suppression efforts

The suppression (i.e., putting out a fire) of any fire requires the constraint of the fire triangle (fuel, heat, oxygen). When the fire does not respond to suppression tactics, it is labelled as “out of control” and is anticipated to grow.^[19] To control a wildfire, different tactics are used, but they should not be used as lone methods. The more action over the three factors, the more prone the fire is to fire suppression.^[20] 

Eliminating the fuel is a common tactic to combat wildfires. This is done by removing the plant material and “drawing” control lines to stop the advance of the fire, as observed in Figure 3. For the reduction of heat, water is usually poured onto the fire. This decreases the temperature and adds humidity to the area. Subsequently, to reduce the oxygen, water, foam, and fire retardants are commonly used. However, the amount and type of fuel, terrain, weather, and fire size determine the best suppression strategy.^[21]

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[1] Rose Morrison, “The Environmental Impact of Wildfires,” Earth.Org, August 18, 2022, https://earth.org/environmental-impact-of-wildfires/.

[2] “Wildfire Smoke – MN Dept. of Health,” accessed August 30, 2023, https://www.health.state.mn.us/communities/environment/emergency/natural/wildfires.html.

[3] Gayle S. W. Hagler et al., “Editorial: Understanding and Communicating Wildland Fire Smoke Risk,” Frontiers in Public Health 9 (September 29, 2021): 721823, https://doi.org/10.3389/fpubh.2021.721823.

[4] Patricia To, Ejemai Eboreime, and Vincent I. O. Agyapong, “The Impact of Wildfires on Mental Health: A Scoping Review,” Behavioral Sciences11, no. 9 (September 21, 2021): 126, https://doi.org/10.3390/bs11090126.

[5] “Wildfires | CISA,” accessed August 29, 2023, https://www.cisa.gov/topics/critical-infrastructure-security-and-resilience/extreme-weather-and-climate-change/wildfires.

[6] “Wildfires | CISA.”

[7] Andrew Moore, “Explainer: How Wildfires Start and Spread,” College of Natural Resources News (blog), December 3, 2021, https://cnr.ncsu.edu/news/2021/12/explainer-how-wildfires-start-and-spread/.

[8] Moore.

[9] “Wildfires,” accessed August 29, 2023, https://www.who.int/health-topics/wildfires.

[10] Volker C. Radeloff et al., “Rapid Growth of the US Wildland-Urban Interface Raises Wildfire Risk,” Proceedings of the National Academy of Sciences 115, no. 13 (March 27, 2018): 3314–19, https://doi.org/10.1073/pnas.1718850115.

[11] Nick Nauslar, “Ask the Scientist: How Can the Weather Spark and Spread Wildfires?,” National Oceanic and Atmospheric Administration, September 4, 2018, https://www.noaa.gov/stories/ask-scientist-how-can-weather-spark-and-spread-wildfires.

[12] Nauslar.

[13] “Fire Fundamentals: Topography,” Charles Darwin University, accessed August 29, 2023, http://learnline.cdu.edu.au/units/env207/fundamentals/topography.html.

[14] “Fire Fundamentals: Topography.”

[15] “Fuels Management,” U.S. Department of the Interior, August 20, 2015, https://www.doi.gov/wildlandfire/fuels.

[16] Vânia R. Pivello et al., “Understanding Brazil’s Catastrophic Fires: Causes, Consequences and Policy Needed to Prevent Future Tragedies,” Perspectives in Ecology and Conservation 19, no. 3 (July 2021): 233–55, https://doi.org/10.1016/j.pecon.2021.06.005.

[17] Marc-André Parisien et al., “Fire Deficit Increases Wildfire Risk for Many Communities in the Canadian Boreal Forest,” Nature Communications11, no. 1 (May 1, 2020): 2121, https://doi.org/10.1038/s41467-020-15961-y.

[18] Parisien et al.

[19] Stephanie Hogan · CBC News ·, “Out of Control, Held, out — What the Stages of Wildfire Mean | CBC News,” CBC, June 9, 2023, https://www.cbc.ca/news/canada/firefighter-terms-control-wildfires-1.6869916.

[20] “Suppressing Wildland Fires,” Information, gov.nt.ca (Government of the Northwest Territories), accessed August 29, 2023, https://www.gov.nt.ca/ecc/en/services/wildfire-operations/suppressing-wildland-fires.

[21] “Wildfire Management Strategies – Province of British Columbia,” gov.bc.ca (Province of British Columbia), accessed August 29, 2023, https://www2.gov.bc.ca/gov/content/safety/wildfire-status/wildfire-response/management-strategies.