As the LA wildfires at the beginning of this year showed — wildfires can have devastating consequences. Wildfires are uncontrolled fires that spread across vegetation, often causing significant environmental and economic damage, and they’re becoming increasingly more common. The total cost of wildfires in the United States is estimated at between $394 billion to $893 billion each year.[1]
We tend to think of all wildfires as the same, but there are actually several different kinds. While they share common causes, wildfires can be categorized based on their behavior, spread patterns and locations.[2] Understanding these distinctions helps with wildfire management and prevention.
Causes of wildfires
Wildfires are a natural part of many ecosystems and some species even rely on them for survival. Burning dead materials allows nutrients to reenter the soil and fuel new growth.
That said, they can also be devastating, destroying homes, wildlife habitats and vast stretches of land. Understanding the causes of wildfires can help in developing strategies to prevent them and minimize their impact.
Humans are responsible for nearly 85% of wildfires.[3] Here are some of the common things that contribute to sparking or accelerating wildfires.
Three types of fires
Now let's look at the different types of fires. These are predominantly classified by where they occur and what they are fueled by. There are also key differences in how hard they are to contain.
1. Ground fires
Ground fires, also known as subsurface fires, burn beneath the surface, affecting organic material like peat, roots and decomposed plant matter. These fires spread slowly and can smolder for weeks or even months without noticeable flames. In some cases, ground fires can even smolder underground through winter months and reignite above ground in the spring.
Differences
- Unlike other wildfires, ground fires burn below the surface, making them difficult to detect and extinguish.
- They spread slowly but can be extremely persistent.
Common Locations
- Peatlands and swamps in Southeast Asia, Canada, and Alaska
- Boreal forests in Russia and Scandinavia
2. Surface fires
Surface fires burn through grass, leaves, underbrush and young trees, remaining close to the ground. These are the most common types of wildfires. Depending on factors like the amount of surface fuel, slope and wind speed and the height of the trees, a surface fire can quickly grow in intensity and expand to consume the forest canopy. At that point, it becomes a crown fire. More on that below.
Differences
- These fires spread quickly but are easier to control compared to ground or crown fires.
- They typically do not cause long-term damage to trees unless they reach the canopy.
Common Locations
- Grasslands and savannas in North America, Africa and Australia
- Forest floors of the western U.S., Canada, and Mediterranean regions
3. Crown fires
Crown fires burn at the tops (canopies) of trees using live and dead foliage and branches for fuel. These fires spread rapidly from one treetop to another. They are usually ignited by surface fires growing in intensity.
A crown fire is considered passive if it involves burning a small group of trees. If it moves from canopy to canopy, it is considered an active crown fire or running fire. These are the most dangerous and destructive wildfires.
Differences
- Unlike surface fires, crown fires burn above ground in the canopy, making them harder to contain.
- They can spread rapidly over large areas due to wind-driven embers.
Common Locations
- Dense forests of Canada, the Amazon Rainforest, and the western U.S.
- Pine and eucalyptus forests of Australia and South America
Protecting yourself from fire
Wildfires come in various forms, each with unique characteristics, causes and impacts. If you live in an area that is prone to wildfires, and particularly difficult-to-contain crown fires, it's important to be prepared. Here are some resources to protect yourself, your home and your assets in the event of a wildfire.
Watching for wildfires: How to stay safe
Does homeowners insurance cover wildfires?
Does car insurance cover wildfires?