Wildfire Causes and Evaluations

This article is part of the Wildland Fire Learning In Depth series. It is designed for anyone who want to learn more about wildland fire.

Wildfires can be caused by nature, such as lava or lightning, but most are caused by humans.

Humans and Wildfire

As many as 90 percent of wildland fires in the United States are caused by humans. Human-caused fires result from campfires left unattended, the burning of debris, negligently discarded cigarettes, and intentional acts of arson.

Cigarettes are one way humans can cause fires.
Cigarettes are one way humans can cause fires.

Nature and Wildfire

Lightning is described as having two components—leaders and strokes. The leader is the probing feeler sent from the cloud. The return streaks of light are a series of strokes that produce the actual lightning bolt or flash that we see.

There are two types of lightning—cold lightning and hot lightning. Cold lightning is a return stroke with intense electrical current but of relatively short duration. Hot lightning has currents with less voltage, but these occur for a longer period of time. Fires are usually started by unusually long-lasting hot lightning bolts.

Lightning is one of the two natural causes of fires.
Lightning is one of the two natural causes of fires.

Evaluation of Wildland Fires

Wildland fire managers must constantly assess the threat of human-caused fire to wildlands and the threat of wildland fires to humans.

When wildfires begin, two major questions are asked:

  • Does the wildfire threaten people and/or their personal property?

  • Where is the wildfire located—in a forest or grassland, or in a human-dominated landscape?

Where people and property are threatened, all efforts are made to extinguish the fire. In some locations, such as large national parks and forests and where the wildfire is started by lightning, a natural fire may be permitted to burn its course to benefit the ecosystem.

By more fully understanding wildfire, managers can better plan for potential desirable and undesirable effects of wildfires. Although managers can be prepared, they cannot predict when or where fires are going to occur.

Remote wildland fire in Sequoia and Kings Canyon National Parks.
If a fire is located in a remote area and poses no threat to people or property, it can be allowed to burn for resource benefit. Sequoia and Kings Canyon National Parks.

Last updated: November 17, 2017