5 Common Causes of Wildfires

By: Jessika Toothman & Yara Simón  | 
Woolsey Fire
A house burns during the Woolsey Fire on Nov. 9, 2018, in Malibu, California. Residents of Thousand Oaks are threatened by the ignition of two nearby dangerous wildfires, including the Woolsey Fire, which has reached the Pacific Coast at Malibu. David McNew/Getty Images

Key Takeaways

  • Burning yard waste, though legal with a permit, can lead to wildfires under certain conditions, such as windy weather. Safety measures include checking with the fire department and maintaining a safe, well-prepared burning site.
  • Machinery, especially with internal combustion engines, can emit sparks and cause wildfires. Spark arrestors help minimize this risk but cannot prevent all equipment-related fires.
  • Unattended campfires, discarded cigarettes and unsupervised children with fire-starting tools are significant human causes of wildfires.

Plenty of natural phenomena can turn the landscape into a blazing inferno and send wildlife racing for safety. Lightning, volcanoes, extreme weather events — all are devastating forces of fiery destruction that can start a conflagration in seconds.

Human activities — such as leaving a campfire unattended, discarding lit cigarettes, debris burning and intentional arson — are among the top causes of wildfires. According to the National Park Service, human-caused wildfires account for over 80 percent of all yearly wildland fires in the United States.


While fire can be fundamental for promoting healthy forest growth, sometimes too much of it is a bad thing, especially when a blaze swells out of control and threatens homes and other important infrastructure. That's where the concept of a wildfire enters the scene. The National Wildfire Coordinating Group defines a wildfire as an "unplanned, unwanted wildland fire" including:

  • Unauthorized, human-caused wildland fires
  • Escaped, naturally caused wildland fires
  • Escaped, prescribed wildland fires
  • Other wildland fires that need to be put out

Sometimes wildfires are set intentionally as an act of arson. It's often tricky for authorities to determine whether arson has actually been committed in wildfires.

Here, however, we'll be focusing on the top drivers of human-caused wildfires, which carry catastrophic ecological and economic consequences. Continue reading to find out how to avoid these fiery mistakes, so you can make Smokey Bear proud the next time you head off into the hills.

5. Burning Debris

Blazing yard waste can get out of hand in a hurry, especially if conditions are particularly hot, dry and windy.

Lots of people burn yard debris, like cut branches and cleared shrubs, after a good garden cleanup. While this practice is usually legal with a permit, it can also be dangerous under certain circumstances.

Weather conditions play a big part in whether it's safe to burn debris or whether your backyard burn could spiral into a wildfire. For example, wind can quickly cause the flames rising off a pile of burning yard waste to spread into unwanted territory.


To prevent an accidental gust from generating a full-fledged wildfire, there are a few steps you can take to help ensure everything proceeds smoothly.

  1. For starters, give the fire department a call the day you plan to burn to get a professional opinion. They may advise you to wait a few days, especially if it's been particularly hot and dry.
  2. Next, determine whether there are any potential hazards either hanging over your intended burn site or located too closely to the perimeter. Ensure there's open space at least three times the height of the debris pile above, and at least 10 feet (3 meters) away horizontally in all directions. That space should be watered down and covered in either gravel or dirt.
  3. After the debris pile burns completely — all under the watchful eye of an observer armed with a precautionary water supply — it should be shoveled over and watered repeatedly.
  4. The site should be checked several times for the next few days and even weeks to make sure all the sparks are fully extinguished.

4. Equipment Issues and Unruly Engine Sparks

Without proper care and maintenance, mechanical devices can spell trouble for a forest.

The invention and eventual mass-production of the internal combustion engine and other now commonplace machinery might have helped modernize society, but they also introduced a new threat to the world's wildernesses. Without the proper precautions, a running engine can spew hot sparks and bits of burning debris — a potentially dangerous situation if that device is operating in a field or forest.

Enter the spark arrestor. It's typically a small device, but it has a big role in protecting against accidental forest fires. Different types of spark arrestors are tailored to work best under different circumstances, but they all basically act like filters that let exhaust out and keep embers in. They're not a 100 percent guarantee against wildfires, but they definitely help decrease the odds that a stray spark will start a blaze.


However, spark arrestors can't stop equipment malfunctions like downed power lines, which can result from lightning strikes, vehicle accidents, a tree branch falling onto the lines or severe weather conditions like storms or ice accumulation. If not promptly detected or controlled, malfunctioning electrical equipment can ignite dry vegetation or other combustible materials nearby and rapidly escalate into a devastating wildfire.

3. Lit Cigarettes

Hey lady — don't just drop that cigarette when you're through. It could cause big problems for your forest buddies.

Cigarettes are among the leading causes of wildfires. Makes sense — they're certainly burning and they're easy to flick out of sight when a smoke break is over. But the careless toss of a still-burning cigarette butt can have serious consequences if it catches a forest on fire.

When out in the woods, smokers need to take special care their habits don't land them in a lot of trouble. Cigarettes butts, cigars and even pipe tobacco all need to be thoroughly ground out in the dirt until you're absolutely certain they're extinguished.


A stump or a log is not a suitable alternative to an ashtray, and it goes without saying that dry grass, leaves and other brush should be avoided. Also, even though it might seem gross to keep an ashtray in the car, it's far worse to simply toss a cigarette out an open car window.

2. Unsupervised Activities

With professional handling, fireworks are plenty safe. But in the hands of amateurs, well that's another story.

It might not seem like a big deal to leave kids to their own devices while parents work nearby pitching the tent or rooting around in the trunk for sleeping bags. But if the little ones get their hands on lighters or matches, that can change everything. Bottom line: Keep a close watch on anything that can start a fire.

If camping is one of your family's favorite activities, consider investing in a good multipurpose fire extinguisher that you can bring along on your trips in case of emergency.


On a similar note, avoid fireworks when there's the chance they could start a wildfire. Sure, they're fun to shoot off, but as soon as they get going — especially the ones that shoot into the air — it's often completely impossible to control the outcome should things start to heat up.

1. Unattended Campfires

The campfire smell that clings to clothes can be a delicious aroma. But if that same campfire causes a wildfire it probably just ends up smelling like shame.

Last, but by no means least, are campfires. Wonderful givers of warmth, light, s'mores and lots more, campfires can also cause wildfires if proper care isn't taken to keep them under control.

Just like with a debris fire, it's important to find a safe location for a campfire that's distanced from nearby ignitable objects and protected from sudden gusts of wind. Campfires should always be built in rock-ringed fire pits that are stocked with a bucket of water and a shovel.


And while it might feel satisfying to establish a roaring bonfire, that's a bad idea; campfires should be kept small and manageable at all times.

On a similar note, when it's time to tuck in, the fire must be extinguished completely. That includes pouring lots of water on all the ashes and embers until the hissing and steaming fully stop, then using the shovel to stir everything around and separate out any bits that are not burnt. Keep it up until you're absolutely certain every last little spark is out.

To learn more about wildfires, forests and the truth about the much-maligned Mrs. O'Leary and her long-beleaguered bovine, hit up the links under Lots More Information.

Frequently Asked Questions

How can I safely extinguish a campfire?
To safely extinguish a campfire, douse it with water, stir the ashes with a shovel and repeat until all embers are fully extinguished and no heat is emitted.
What precautions should I take before burning debris?
Before burning debris, ensure it's a legal activity, secure any necessary permits, check weather conditions, maintain a safe distance from flammable materials and have water or a fire extinguisher nearby.

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • "Fireworks Illegal on all Public Lands in Idaho." U.S. Department of the Interior Bureau of Land Management. June 29, 2009. (1/21/2010) http://www.blm.gov/id/st/en/info/newsroom/2009/june/fireworks_illegal.html
  • "Fireworks Restrictions in Place." U.S. Forest Service. June 27, 2002. (1/21/2010) http://www.fs.fed.us/r6/centraloregon/news/2002/06/020627fireworks.shtml
  • Pollick, Michael. "What is a Spark Arrestor?" WiseGeek. (1/21/2010) http://www.wisegeek.com/what-is-a-spark-arrestor.htm
  • "NWCG Communicator's Guide for Wildland Fire Management." National Wildfire Coordinating Group. (1/21/2010) http://www.nifc.gov/preved/comm_guide/wildfire/FILES/PDF%20%20FILES/Linked%20PDFs/2%20Wildland%20fire%20overview.PDF
  • "Wild & Forest Fire." NOAA Economics. (1/21/2010) http://www.economics.noaa.gov/?goal=weather&file=events/fire/
  • SmokeyBear.com Web site. (1/29/20)10 http://www.smokeybear.com/index.asp
  • "Wildland Fire -- An American Legacy." U.S. Department of Agriculture Forest Service. Summer 2000. (1/21/2010) http://www.fs.fed.us/fire/fmt/fmt_pdfs/fmn60-3.pdf