Man vs Nature: Understanding What Causes Wildfires and How We Contribute

Wildfires can occur anywhere in the world, except Antarctica. On average, most wildfires are caused by humans.

When conditions are right, wildfires can be caused by simple human activities like building a campfire. 

Wildfires can be caused by natural events such as lightning strikes and volcanic eruptions.

Wildfires need a heat source, fuel, and oxygen to start and spread. Without these three ingredients working together, wildfires can’t occur. Topography, weather conditions, and fuel influence how wildfires spread.

What Causes Wildfires?

Most wildfires are caused by humans, whether accidental or intentional. According to the National Interagency Fire Center, human-caused wildfires account for 87% of all wildfires in the US, based on a 10-year average.

Climate change and weather conditions play a major role in wildfire threats and spread. Lightning is one example of a natural event that can start a wildfire.

Human-Caused Wildfires

More than half of the wildfires in the US are caused by human activities. There are several ways wildfires can start. Weather conditions can impact the flammability of vegetation. Dry periods and droughts can increase the risk of wildfires.

Many states have burn laws that prohibit people from burning debris or building campfires at certain times of the day and year.

For example, Virginia has a 4 PM Burning Law, which restricts open-air burning between February 15 and April 30 each year. Open-air burning is restricted until 4 PM during this time of year.

Other states have similar laws, but local counties and cities can also enforce restrictions and bans according to wildfire threats.

Arson

Arson is the intentional act of setting fire to property. Wildfires started as a result of arson may be considered third-degree arson because they involve setting fire to unoccupied lands, such as forests.

Arson is a felony crime in most cases. States and localities have different laws against arson, with differing degrees of punishment depending on the nature of the crime.

Individuals who commit arson may be punished with jail time and/or fines, depending on the severity of the act. 

Arson shouldn’t be confused with juvenile acts of setting fire, as arson is generally described as setting fire to property to deliberately cause damage or harm.

According to the National Interagency Fire Center, arson can account for more than 20% of human-caused wildfires.

Debris Burning

Open burning or out-of-control debris burning are two factors that can cause wildfires. 

If proper precautions aren’t taken during open or debris burning, it can cause a wildfire. Proper containment is necessary to prevent open burns from escaping.

Debris and open burning can include burning debris piles in one’s yard, burn barrels, trash burning, and land clearing.

Most states have certain laws pertaining to open burning to reduce the risk of wildfires. Burn laws are enforced at the local and state government level.

State land management agencies, such as the Department of Forestry, are responsible for monitoring weather conditions and enforcing burning laws. 

If areas are experiencing especially dry or windy conditions, burning laws may be enforced to prevent wildfires from starting.

Debris burning can get out of control in windy conditions, even if it’s contained properly. Wind can carry burning embers from a fire and ignite nearby dry vegetation.

Campfires

Similar to debris and open-air burning, campfires can cause wildfires if they’re not contained or extinguished properly.

The US Department of Agriculture (USDA) recommends building a campfire within a ring of rocks to keep it contained. 

All vegetation and other flammable materials, such as logs, sticks, or leaves, should also be removed from the surrounding area.

Campfires can burn for several hours, depending on how much firewood is added. A campfire should never be left unattended. To properly extinguish a campfire, it should be doused with water until it’s cold.

According to the USDA, escaped campfires are the second most common way wildfires are started in national forests.

Campfire burn restrictions may be enforced by national and state parks when weather conditions create suitable wildfire conditions.

Vehicles and Equipment

Vehicles and power equipment are capable of starting wildfires in vulnerable areas. Sparks from poorly maintained or faulty vehicles and power equipment can start wildfires in dry grasses and vegetation.

Lawnmowers can create sparks if they hit rocks or pieces of metal in yards or fields.

Exhaust pipes from vehicles can heat up to 1,000°F (538°C), which is hot enough to ignite dry vegetation.

Equipment and vehicles used in vulnerable areas should receive regular maintenance to reduce the risk of starting a wildfire.

Use of Firearms and Explosives

Wildfires can be caused by firearms and explosives when proper safety precautions aren’t taken.

A study was conducted by the USDA Forest Service and Rocky Mountain Research Station to test how ammunition can ignite organic matter.

In the study, it was determined that bullets composed of lead, steel, and copper are capable of igniting organic matter when kinetic energy is converted to thermal energy upon impact with a target.

The moisture of organic matter, level of relative humidity, and air temperature, combined with bullet composition and target material, can play a role in ignition capabilities.

A report released by the USDA Forest Service and Missoula Fire Sciences Laboratory determined that 1.2% of human-caused wildfires were attributed to fireworks, firearms, and explosives.

Natural Wildfire Causes

Although human-caused wildfires make up a significant portion of all wildfire causes, wildfires can occur naturally.

Wildfires are considered natural disasters and may be allowed to burn if humans and properties aren’t threatened.

Natural wildfires can be beneficial to ecosystems because they allow new vegetation to grow. Wildfires can be caused by natural phenomena such as lightning, volcanic activity, and coal seams.

Lightning

When lightning strikes an object, such as a tree or shrub, it can ignite it. A lightning strike is so hot that it can heat the surrounding air temperature up to 50,000°F (27,760°C).

Lightning is one of the major causes of natural wildfires. Some areas that experience a higher frequency of thunderstorms may be more susceptible to lightning-caused wildfires.

Lightning that strikes the Earth’s surface during dry thunderstorms is more likely to ignite. 

Without heavy rainfall, vegetation remains dry and can ignite if struck by lightning. Dry thunderstorms are fairly common in the American West due to the lack of moisture in the air.

Dry periods or droughts can make organic materials more flammable and at-risk of igniting by lightning during a thunderstorm. If lightning strikes dry organic matter, it can continue to smolder and turn into a wildfire if conditions remain dry.

According to the NIFC, there were 7,467 lightning-caused wildfires documented in the US in 2022. The southern region of the US had the most lightning-caused wildfires compared to other regions.

A total of 68,988 wildland fires were documented in 2022. Therefore, lightning was only responsible for about 11% of all wildfires reported in the US that year.

Volcanic Activity

Volcano eruptions can trigger wildfires because hot lava is capable of igniting dry vegetation.

Since more than half of the Earth’s volcanoes are located along tectonic plate boundaries, volcano-caused wildfires are less common compared to lightning-caused wildfires. It’s also important to note that not all volcanoes are active or experience continuous eruptions.

The Mother’s Day lava flow caused by the eruption of a volcanic cone called Pu`u `O`o caused the Kupukupu Fire in 2002 on the island of Hawai’i. The wildfire started due to hot lava igniting dry vegetation.

Coal-Seam Fires

Wildfires can be caused by the underground smoldering of coal. Coal seam fires can be triggered by human activities, but they can also occur naturally. 

Coal beneath the Earth’s surface can ignite if enough pressure and oxygen provide the right conditions.

Although any wildfire can be disastrous, coal seam fires can be especially harmful because they can produce toxic fumes. Coal seam fires can be difficult to detect because heating starts below the Earth’s surface.

Satellites in space that collect infrared data allow scientists to study weather events, climate change, and the Earth’s features that may not be visible to the human eye. 

Infrared data can be used to detect changes in the Earth’s surface temperature caused by underground heating.

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High-Risk Wildfire Conditions

Wildfires can start and spread easily if the conditions are right.

The three main ingredients needed for a wildfire to start or spread include:

• Fuel
• Oxygen
• Heat

These three components make up the fire triangle.

The fuel of a wildfire is any flammable material capable of igniting and burning to allow a wildfire to start and spread. 

Oxygen is a chemical element needed for a fire to burn, as it plays an important role in a chemical process called oxidation. Without oxygen, fire can’t burn.

The National Fire Danger Rating System (NFDRS) is used to determine the level of fire danger in a particular area. Fire managers assess conditions on a daily basis to inform the public of fire dangers based on things like relative humidity and wind speeds.

If an area is experiencing dry and windy weather conditions, the fire danger level will be higher.

Heat is also needed in order for fuel to reach temperatures hot enough to ignite. The three components of the fire triangle are targeted when putting out wildfires. Removing one or more of these elements can help control and extinguish a fire.

Fire Danger Levels

Based on the NFDRS, there are five fire danger levels in the US. Fire danger levels start at low levels, and the severity of fire danger increases with each level. 

Depending on the fire danger level, controlling and extinguishing a wildfire can be easy or very difficult.

Your local fire department may have a fire danger rating sign posted on their property to inform local residents of the fire danger level for the day.

State and national parks usually have these signs posted around the park to inform visitors about fire danger levels and encourage them to be mindful of their activities, such as building a campfire.

Based on the collection of various sources of data, the US Geological Survey has a Wildland Fire Potential Index (WFPI) application you can use to view fire danger areas across the US.

Your state’s Department of Forestry may also provide information on fire danger levels in your area.

Low Fire Danger Level

The color code for low fire danger level is green and is considered fire danger level 1 or “Class 1.” This means that fuel is unlikely to be ignited. If a wildfire starts when the fire danger level is low, it’s more likely to be easily controlled.

Wildfire threats associated with campfires or other burning activities are generally not as high at this level.

Moderate Fire Danger Level

Fire danger level moderate is level 2, or “Class 2,” and has a blue color code. A moderate fire danger level means that accidental fires can start, but risk levels are still generally low.

Precautions should still be taken when participating in debris or open burning, building campfires, or similar activities.

If a wildfire starts in a moderate fire danger environment, it may spread and burn quickly if the conditions are right. However, burns may be slow or moderate. These fires are unlikely to become severe and are usually still easy to control.

High Fire Danger Level

Wildfires are more likely to start if an area has a high fire danger level. This is a level 3, or “Class 3,” with a yellow color code.

Vegetation or fuel is considered easily ignitable. Campfires or debris-burning fires are more likely to escape and more difficult to control. If the fire danger level is high, local areas may enforce burning bans until the fire danger level is lowered.

If fires get out of control at this level, they can be very difficult to control.

Very High Fire Danger Level

A very high fire danger level has an orange color code and is described as level 4 or “Class 4”. At this level, fires can start very easily. Fuel can be easily ignited, and the fire can spread and increase in intensity very quickly.

If a fire escapes at this level, it can be very difficult to control at the start of ignition. When the fire danger level is very high, wildfires are very likely to grow larger and last longer compared to lower fire danger levels.

Extreme Fire Danger Level

The highest fire danger level is extreme. This danger level is 5, or “Class 5” with a red color code. Local areas are likely to implement restrictions on burning when the fire danger level is extreme.

Fires are very likely to start from all causes and can quickly become intense and out of control. Small fires, such as escaped campfires, are more likely to grow much quicker.

If a wildfire occurs when the fire danger level is extreme, controlling and extinguishing it can be very difficult. Wildfires may last for several days or more.

How Wildfires Spread

Wildfires can spread when fire danger levels are moderate, high, very high, or extreme. 

Although it’s unlikely for wildfires to spread or get out of control when the fire danger level is low, it’s still possible.

There are a few components involved when a wildfire starts to spread. Similar to the fire triangle, the wildfire behavior triangle includes three components that influence the spread of wildfires.

The three elements of the fire behavior triangle include:

• Fuel
• Weather
• Topography

These elements play a significant role in how wildfires behave. Wildfires need fuel to start and spread. If a wildfire runs out of fuel, it may weaken and be extinguished easily.

The moisture level and density of vegetation affect how a wildfire burns. More dense fuel is likely to burn slower and longer, while less dense materials can burn quicker.

If moisture levels are high, a wildfire may not burn as intensely or quickly compared to fuel with a low moisture level.

If weather conditions include high winds and very low humidity, wildfires are more likely to spread faster and become more intense. 

Winds can help a wildfire spread by providing it with oxygen and moving it toward more flammable materials.

Topography can influence how a wildfire spreads because sometimes wildfires may be easier to control if they hit a natural barrier. For example, a river may help reduce the spread of a wildfire by preventing it from traveling to a new area across the river.

Other land features that can influence the spread of wildfires include slopes and canyons.

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How Are Wildfires Suppressed?

Wildfires can be controlled and extinguished naturally or by firefighters. The biggest priority in wildfires is to protect humans.

There are multiple levels of suppression that may be implemented depending on the severity of the wildfire and its danger to humans and property.

Sometimes limited action may be taken to allow a wildfire to run its course and benefit ecosystems. 

However, if humans or infrastructure are at risk, then full suppression procedures are usually implemented to get it under control and put out as soon as possible.

Fire crews may use the following suppression procedures to control and extinguish a wildfire:

• Redirecting the fire
• Dousing the fire with water or fire retardant from the ground, by plane or helicopter
• Removing fuel (dry vegetation or logs) to prevent the wildfire from spreading to another area

Fire crews first assess what causes wildfires before implementing suppression plans.

The size of the fire, its behavior, growth potential, and location are all factors considered when assessing a wildfire. 

Once the wildfire has been assessed, fire crews must determine the best course of action to reduce the amount of damage it could cause.

Assessments are also conducted to determine the threats of a wildfire, such as:

• Threats to human life and property
• Threats to infrastructure (roads, power stations, and pipelines)
• Threats to protect areas, wildlife, and ecosystems

Human life is the most important thing when considering the threats of a wildfire. If a wildfire is severe and expected to spread rapidly before it can be extinguished, people may be ordered to evacuate the area.

A wildfire’s fuel, heat, or oxygen must be removed to extinguish it. Fire crews may target one or more of these three elements to control a wildfire and put it out.

Fuel may be removed by clearing land and flammable debris that would otherwise allow the wildfire to spread. 

Heat can be removed from a wildfire by using water or fire retardant from wildfire engines or special helicopters and planes.

Wildfires can be suppressed naturally if they encounter a natural barrier. Weather conditions can also support suppression if wind speeds decrease and the relative humidity increases.

Although water can put out fires, precipitation alone usually isn’t enough to completely suppress a wildfire.

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Wildfire Statistics

On average, the number of wildfires and acres burned has steadily increased over the last few decades. A number of factors have contributed to this increase, including climate change.

Wildfire seasons have become longer due to prolonged dry periods and higher air temperatures. About 70,000 wildfires occur each year in the US, based on NIFC data collected since 1983.

Data has also shown that the wildfire season is starting earlier in the year in many regions. 

For example, US wildfire seasons between 1984 and 2001 typically peaked in August. In recent years, the peak of the wildfire season has begun in July.

Due to the increase in wildfires, the cost to fight them and repair any damage caused has also increased.

According to the Western Fire Chiefs Association, wildfires in the US are most common in Western states.

The climate in the American West is very hot and dry during the wildfire season. Although many areas experience high amounts of rainfall, several regions experience severe droughts that increase the risk of wildfires.

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Record-Breaking Wildfires

Severe wildfires have the potential to burn hundreds of thousands to millions of acres. 

Some of the most extreme wildfires are associated with drier than normal seasons. Based on the acreage burned, these are some of the largest wildfires in the last 20 years.

2003 Siberian Taiga Fires

During the 2003 wildfire season, the Siberian taiga suffered devastating wildfires that burned up about 55 million acres of grasslands, pine forests, and other vegetated lands.

According to the Global Fire Monitoring Center, the Siberian taiga experienced extreme drought, inappropriate forest management, and reduced capabilities for fire management in 2003.

Areas affected by drought experienced extremely low precipitation levels from August 2002 to May 2003. Some regions, such as the Buryatia Republic, had as little as 3.6 cm of rainfall during the 10-month period.

2019-2020 Australian Bushfires

Australia had one of its most severe wildfire seasons, starting in the spring of 2019 and continuing on until March 2020. 

The affected territories experienced several periods where the fires worsened due to drought and increasing temperatures.

Heavy rainfall eventually came in early 2020, but it wasn’t enough to suppress them. The wildfires lasted for nine months before they were extinguished or brought under control.

The Australian bushfires caused a significant amount of damage, burning through more than 46 million acres. About 15 million acres were burned in the Northern Territory alone. Thousands of homes were destroyed by the fires.

According to University of Sydney ecologist Chris Dickman, it’s estimated that more than one billion animals were killed as a result of the fires.

2020 California Wildfire Season

One of the worst wildfire seasons the state of California has experienced occurred in 2020. According to the California Department of Forestry and Fire Protection, a total of 8,648 wildfires burned about 4.3 million acres across the state.

More than 10,000 homes were destroyed, and 33 people died as a result. More than 100,000 people were evacuated from their homes and communities.

Based on acreage burned, the 2020 California wildfires broke the record for the largest wildfire season that the state has seen in modern history.

A combination of thunderstorms, heat waves, and winds helped ignite and fuel the fires.

2023 Canadian Wildfires

At the time of writing, wildfires are overwhelming Canada. As of the first week of July 2023, more than 300 wildfires had continued to remain out of control. 

The number of active wildfires has reached above 600, and more than 21 million acres have been burned.

Most of the Canadian wildfires started due to lightning, while others were ignited by human activity. Reports of the first wildfires started around late April or early May, lasting for more than 2 months.

In June, the smoke emitted from the Canadian wildfires reached the states. Some cities, such as New York, have experienced hazardous air quality levels with reduced visibility.

While Canada’s wildfire season typically peaks in July–August, the 2023 Canada wildfire season has already broken the country’s record for the largest wildfire in terms of acreage burned.

Effects of Wildfires on Humans and the Environment

Wildfires can have a devastating impact on human health and the economies of affected areas.

Air quality can reach hazardous levels due to the thick clouds of smoke wildfires are capable of producing. Poor air quality can be especially hazardous to vulnerable individuals, such as older adults, young children, individuals who work outside, and people with respiratory illnesses.

Tens to hundreds of thousands of people may be displaced from their homes if wildfires spread to their communities. Hazardous air quality levels can also create unlivable conditions and force people to evacuate.

The damage that wildfires cause and the cost to fight the fires can have a great impact on a state’s and a nation’s economies.

According to the Congressional Budget Office, $2.5 billion of federal spending was distributed for fire suppression between 2016 and 2020. This number doesn’t include disaster relief for wildfires, which totaled $5 billion.

Although severe, uncontained wildfires can be disastrous, there are some benefits that wildfires have on the environment, such as:

• Clear overgrown areas to allow new plants to grow
• Provides soil with valuable nutrients
• Creates new habitat for plants and animals
• Kill invasive species and diseases harmful to native wildlife

Wildfires can be harmful to native wildlife. Large wildfires can kill millions to billions of animals due to habitat loss, poor air quality, and contaminated drinking water.

How to Prevent the Spread of Wildfires

Since most wildfires are started by people, there are a few things you can do to help stop them. One of the best ways to help prevent wildfires is to stay informed about local fire danger levels.

If you plan on burning debris or building a campfire, check your local fire danger level beforehand to ensure that your area doesn’t have burn restrictions or hazardous fire danger levels.

Other ways you can prevent wildfires include:

• Prepare campfire pits properly and make sure the fire is completely out before leaving it
• Never leave a fire unattended
• Don’t build a fire if it’s windy or relative humidity levels are low
• Clear the area surrounding your firepit from dry vegetation and any flammable material
• Be prepared in case a fire escapes by having fire retardant or ample water ready

Although wildfire season begins in the spring and lasts throughout the summer in many regions, climate change has increased the risk of wildfires year-round. 

Prolonged droughts, shorter winters, and rising air temperatures are all contributing factors.

Even if there aren’t any burn bans in your area during the fall and winter, precautions should still be taken during these wetter, colder months.

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