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)