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What are 90% of wildfires caused by?

Published in Wildfire Causes 3 mins read

Humans are responsible for nearly 90% of wildfires, primarily through various preventable activities.

Understanding Wildfire Origins

In the United States, the overwhelming majority of wildfires, nearly 90%, originate from human activity. These incidents are largely preventable and stem from common actions that inadvertently spark destructive blazes across landscapes. Understanding these predominant causes is crucial for developing effective prevention strategies and promoting public safety.

Primary Human Causes of Wildfires

Human-caused wildfires result from a range of activities, often due to negligence, lack of awareness, or accidental actions. Recognizing these primary causes highlights the critical role of public awareness and responsible behavior in preventing wildfire outbreaks.

Here are the most common human-caused origins of wildfires:

Cause Description
Discarded Cigarettes Improperly disposed of or still-smoldering cigarettes can easily ignite dry vegetation, especially in areas with high fire danger. Even a small ember can quickly escalate into a large fire in receptive fuels.
Unattended Campfires Campfires left burning without proper extinguishment are a significant source of wildfires. Embers can easily blow away and start new fires, or smoldering logs can reignite hours later if not thoroughly doused and stirred.
Burning Debris Controlled burns, such as those for agricultural clearing or yard waste, can quickly escape containment and become uncontrolled wildfires if not carefully managed or conducted in unsafe weather conditions (e.g., high winds, low humidity).
Equipment Malfunctions Sparks from machinery, vehicles, or power tools (like chainsaws, grinders, or mowers) can ignite dry grasses or brush. This is particularly common during agricultural work, construction, recreational vehicle use, or even roadside activities where hot vehicle parts come into contact with dry fuels.

Natural Causes of Wildfires

While human activity accounts for the vast majority of wildfires, some fires do occur naturally. These non-human phenomena are considerably less common but can still trigger significant blazes, especially in remote or wilderness areas.

Key natural causes include:

  • Lightning Strikes: A common natural ignition source, especially in remote areas where dry lightning storms (thunderstorms that produce little or no rain at the ground) can occur. Lightning ignitions can sometimes smolder for days before becoming active fires.
  • Volcanic Eruptions: Though extremely rare as a widespread wildfire cause, volcanic activity can generate extreme heat and molten material capable of starting fires in surrounding vegetation.

Understanding the distinction between human-caused and natural fires helps to focus prevention strategies where they can have the greatest impact. For more comprehensive information on wildfire causes and prevention, resources like the Western Fire Chiefs Association provide valuable insights.