Wildfires 101 | National Geographic

• [Narrator] On average, wildfires burn up to five million acres of land in the United States each year. While they can start naturally, wildfires are often caused by humans with devastating consequences.

Wildfires are large, uncontrolled infernos that burn and quickly spread through wild landscapes. Types of wildfires may include forest, brush, and peatland fires, depending on the landscapes affected.

Wildfires require three components, known as the fire triangle: a heat source, fuel, and oxygen. Heat sources, such as the sun, a hot bolt of lightning, or a smoldering match, can supply enough heat to spark a fire. That spark then turns into flames when fuel or any flammable material is present.

Dry, dead grasses, leaves, and trees are common fuels for wildfires, but so are living vegetation, called green fuels. Pine trees and other evergreens contain flammable oils that can burn when exposed to a heat source. As the fuel burns, the resulting flames feed and thrive off of oxygen.

When air movement or wind occurs, not only is more oxygen supplied to the fire, but it may also help transport and spread the flames. Since wildfires occur outdoors, they have a nearly endless supply of oxygen from our atmosphere to burn.

Many wildfires are the result of natural causes. A warmer climate and weather patterns like El Nino can create the hot, dry conditions necessary for fires to erupt. However, about 90% of wildfires are caused by human activity, such as campfires that become uncontrollable, improperly handled cigarettes, or arson.

Although wildfires occur worldwide, they are most common in the Western United States. There, high temperatures, drought, and frequent lightning and thunderstorms can create the perfect setting for wildfires.

While they can be destructive, and sometimes even deadly for humans, wildfires do play an important role in nature. They can help a forest by removing harmful insects or diseased plants, and they can clear thick canopies to help sunshine reach seedlings on a forest floor.

By being aware of the conditions necessary for wildfires to occur, they can be managed and prevented, thereby saving lives and making way for the positive effects of wildfires. (gentle music)