A common culprit behind most wildf ires
Winds can stoke flames that spring up when sparks hit dry tinder, when an electrical line falls, or a cigarette is tossed from a car window
Aside from lightning, when fires ignite in California, it’s a safe bet humans had a role.
Wildfires can start in a variety of ways.
Mostly, they’re caused by humans — by our activity or equipment. A study published in 2017 found that 84% of U.S. wildfires were caused by human-related activity; the remaining 16% were caused by lightning. About 95% of fires the California Department of Forestry and Fire Protection responds to are caused by humans.
Here are some ways wildfires are ignited in California:
Power lines/electrical equipment: Electrical lines and related equipment can break in high winds and spark, igniting tinder-dry vegetation that can spread quickly in high winds.
Pacific Gas & Electric’s electrical transmission lines sparked the Camp fire — the deadliest and most destructive wildfire in California history — in 2018. That blaze razed 90% of the town of Paradise, killed 86 people and destroyed more than 13,900 homes. The lines malfunctioned on a dry hillside near a windy canyon.
Southern California Edison and San Diego Gas & Electric power lines have also ignited some of the largest fires in modern California history, as has a privately owned electrical system.
Sparks from vehicles or other equipment: A trailer with a flat tire that resulted in the wheel’s rim kicking up sparks caused one of California’s most destructive wildfires, the Carr fire in Shasta and Trinity counties, which destroyed more than 1,600 structures and killed eight.
Other common causes are lawnmower blades or metal weed-whackers striking rocks to create sparks, and vehicle collisions. Sparks from a metal grinder jumped into dry grass, triggering the Zaca fire in Santa Barbara County in 2007 — one of the largest in state history.
Chains hanging from a boat or truck trailer can ignite fires; so can hot components underneath a vehicle when parked near dry brush. “You don’t think about it when you drive off to the side of the road,” said Jennifer Balch, lead author of a study on human-caused wildfires and director of Earth Lab at the University of Colorado in Boulder.
Arson: Arson is a rare cause of the most catastrophic wildfires in California. In 2006, Raymond Lee Oyler, an accused serial arsonist, used a combination of matches and cigarettes to start a fire at the base of the San Jacinto Mountains, prosecutors said. Five firefighters died fighting the blaze; Oyler was sentenced to death in 2009.
A 23,000-acre fire in Orange and Riverside counties in 2018 was allegedly set by Forrest Gordon Clark; he has pleaded not guilty.
Campfire: An illegal campfire ignited by a deer hunter caused a wildfire that burned more than a quartermillion acres in mountainous forests near Yosemite in 2013 and threatened a vital supply of water for San Francisco. In a signed affidavit,
Keith Matthew Emerald said embers from his campfire blew up the hill and ignited brush. Charges against him were later dropped.
Cigarettes: Cal Fire responds to an average of 47 wildfires each year caused by carelessly discarded cigarettes.
Call for help: A deer hunter lost in the backcountry of northern San Diego County set two small signal fires. That caused the Cedar fire of 2003, killing 15, burning more than 2,800 structures and more than a quarter-million acres. The hunter was sentenced to six months in a work-furlough program.
Faulty wiring: A hot tub’s faulty wiring caused a 76,000-acre fire in Lake County, causing the deaths of four people and destroying nearly 2,000 buildings in 2015.
Failure to extinguish a previous fire: The OaklandBerkeley hills fire of 1991, which killed 25 people and destroyed more than 2,200 homes, blew out of control in swift winds after firefighters failed to fully monitor and extinguish a fire the previous day that had been thought to be controlled.
Lightning: It’s not a particularly common cause among California’s most destructive or deadliest fires, but it has caused a fair number of the state’s largest. In 2012, lightning ignited the Rush fire in Lassen County, burning more than 270,000 acres in California; an additional 44,000 acres burned in Nevada.
Fear of insects: A rancher tried to plug a wasp’s nest in the ground by jamming a stake into the ground. That created a spark that began burning waist-high grass. He tried to smother the flames by tossing a trampoline on it, but that just fed the flames. It caused one of two fires that merged to become California’s largest wildfire on record, the Mendocino Complex fire, which burned more than 450,000 acres in Colusa, Lake, Mendocino and Glenn counties.
Are California’s wildfires getting more destructive?
All 10 of the most destructive wildfires in modern California history have occurred since 1991.
Why is this? Lots of reasons. Here are some:
We continue to build and live in the wilderness. Some experts say we need to stop building homes in wildlands at risk for wildfires.
Once a wildfire ignites homes, it can become an urban firestorm — moving horizontally, house to house, as it did in the town of Paradise in 2018. Such fires can be fueled more by igniting homes than the surrounding trees.
Hotter, drier weather: Higher temperatures are causing vegetation to get more dried out than ever. Climate change is also linked to drier autumns in California and a delayed onset of autumn rains.
That’s a big problem: Firefighters historically relied on early rains to ease the threat from extreme winds that plague California beginning in late September.