How do Wildfires Start?

We’ve all heard the famous refrain, “Only you can prevent forest fires.” While it’s true that humans are the catalyst for many fires, we’re not the only culprits. There’s more than one way a wildfire can start—from human negligence to natural causes to natural causes made worse by human influence. If you’ve ever been curious to know more about how wildfires start and what makes them spread, you’ve come to the right place.

Wildfires caused by humans

Brace yourself for an uncomfortable fact: The US Department of the Interior estimates that as many as 90% of wildfires are caused by human activity. In this category, they include “campfires left unattended, the burning of debris, downed power lines, negligently discarded cigarettes, and intentional acts of arson” as common avenues for human-induced wildfires. That’s why fire safety is so important and so frequently discussed. Education and awareness are key in preventing human-caused wildfires that damage or destroy homes, communities, and ecosystems.

Make sure you and your family do your part during fire season, and at all times of year. Properly dispose of cigarettes. Completely and thoroughly douse campfires when you’re done with them, and never leave them unattended while burning. Don’t start campfires or burn debris in dry places or whenever there’s a burn ban in effect in your area. Talk about fire protection and safety with children often so they grow up with a keen awareness of best practices to keep themselves and their communities safe during wildfire season.

Wildfires started by natural causes

The US Department of the Interior describes the other 10% of wildfire causes as “natural.” The types of fire-causing natural disasters they include in this category are lightning strikes and lava. And while they don’t list an estimated percentage, even the number of fires caused by these geological and weather conditions would certainly be fewer if it weren’t for harmful human influences. This brings us to the topic of climate change and how it’s impacting the wildfires we experience.

The impact of climate change on wildfire causation

Sadly but unsurprisingly, human-caused climate change is having an increasingly greater effect on the number and intensity of wildfires we experience. To put it simply, environmentally damaging human activity is causing our planet’s climate in general to get drier and hotter. Although the earth’s temperature has been rising steadily for some time, the pace is definitely accelerating. According to the NOAA National Centers for Environmental Information, the ten warmest years in the planet’s recorded history have all occurred since 2005. These high temperatures go hand in hand with drought conditions and high winds, which create a perfect situation for higher, hotter, wildfires that spread even more quickly and are deadlier than ever.

How wildfires spread

Before we talk about how a wildfire spreads, we have to understand how a wildfire starts. That’s where the fire triangle comes in. This term refers to the three elements that have to coexist for a wildland fire to start. They are: heat, oxygen, and fuel. As we’ve already covered, the heat source is typically either lightning, or a human cause like a lit cigarette or neglected campfire. When the heat source has fuel, like dry vegetation that’s either naturally occurring or is a result of drought, a fire can start all too easily. Add an oxygen source like high winds to blow sparks and embers toward additional fuel, and that’s how a fire spreads.

That’s why preventing wildfires from starting and spreading involves a multi-pronged approach. Since high winds aren’t preventable (except by taking collective action to halt climate change), we have to focus on prevention from the other two corners of the fire triangle. To minimize the danger of heat sources that can spark fires, taking great care with common ones like cigarettes and campfires is wise. To minimize fuel availability for wildfires that do get started, mindful water consumption and prescribed burns done by the forest service are two helpful tactics.

Why highly destructive wildfires are more common in California

When you hear about US wildfires in the news, they’re usually happening in the state of California. States like Oregon, Texas, Colorado, and Montana have their share too, but the Golden State is almost always the chart-topper. It’s commonly cited as the most at-risk state for wildfires, and had the most of any state last year—9,000 separate blazes that burned over two million acres of land. Why is it that California wildfires are so common? We have a full blog post going over why they are so common in California, but we have condensed them into the following reasons:

• • Overdevelopment of the wildland-urban interface (WUI). Many of California’s 40 million residents live in areas known as wildland-urban interfaces. These are regions where natural areas like forests abruptly meet developed land like towns and cities. That means wildfires that start in thick forests can easily spread to inhabited areas, causing more damage to homes and communities.

• A long dry season. Most of California’s rainfall happens in autumn and winter—though the state has been increasingly getting less moisture even during this time due to climate change. That means long, hot, and dry spring and summer seasons. Vegetation has these long months to dry out or even die, resulting in a wealth of flammable material that can quickly turn a spark into an uncontrolled fire.

• Strong winds. Ever heard of the Santa Ana winds? If you’ve ever lived in southern California, you’re certainly familiar with these well-known seasonal winds. They blow in from the Great Basin area down into southern California from October to April. They’re a perfect example of the “oxygen” element of the fire triangle that can rapidly spread any fires that may start.

Protecting your home from wildfire danger

It’s up to all of us to practice fire safety in our own lives, and to fight for collective action against climate change. Prevention is key—but so is protection against the fires that will still inevitably happen. If you live in an area that’s at risk for wildfires, now’s the time to take action to keep your home safe. Contact Ember Defense today to learn more about the wide array of home hardening techniques we can help you with to preserve your family’s house in the event of a wildfire: (415) 573-2400.