Wildfires have plagued California for years. How often is arson to blame?

San Bernardino County authorities announced this week that a 34-year-old man had been arrested and accused of igniting the Line Fire, which has burned more than 37,000 acres in San Bernardino County.

So how often is arson to blame for wildfires in California?

What do the numbers show?

Gianni Muschetto, staff chief of law enforcement at Cal Fire, said about 10-15% of wildfires in the last five years were the result of arson.

Pointing to published data from 2022 as an example, he said there were 358 arson fires in the state that year, amounting to about 12,000 burned acres. Each time, firefighters and members of the public were put at risk.

“It’s not an accident, it’s not lightning. It’s a reckless or malicious act,” Muschetto told LAist.

He mentioned the Park Fire, which fire authorities have said was set in July by a man accused of pushing a burning car down a gully near Chico. It’s reportedly the fourth-largest wildfire in recorded state history.

The blaze burned nearly 430,000 acres in Butte and Tehama counties.

“None of us, in our lifetime, are going to see those forests come back to what they were,” Muschetto said.

What are the common causes of wildfires?

Wildfires can be started by natural causes, like a lightning strike, but far more often people are to blame. According to the National Park Service, nearly 85% of wildland fires in the U.S. are caused by human action.

Fire officials often point to neglecting campfires, operating machinery (like a faulty lawnmower) or discarding lit cigarettes as ways people may unintentionally ignite dry brush.

But there are times when it’s no accident. It’s arson.

In 2022 and 2021, Cal Fire identified arson as a cause in more than 350 fires each year, according to the department's most recent published data. Arson was the cause more often than campfires, playing with fire, electrical power, lightning and smoking.

But it was less than a few other causes, like burning debris. In one of those years, 2021, there were more fires caused by vehicles — 419 — than arson.

Cal Fire authorities had more recent data for arson-related arrests. Those arrests nearly doubled last year when compared to five years earlier. Last year, there were 111 arrests on suspicion of arson in Cal Fire areas. In 2018, there were 61.

Within that five-year stretch, the most arson-related arrests happened in 2022, when there were 162, according to Cal Fire.

Muschetto attributed the higher numbers, in part, to video evidence captured on cellphones and home security cameras.

“It allows us to identify those responsible for starting fires a lot more than we’ve been able to in the past,” he said.

How can suspected arson be reported?

Members of the public can call Cal Fire’s hotline if they suspect arson. The phone number is 800-468-4408.

Callers can remain anonymous.

What are some notable arson arrests?

Line fire — Justin Wayne Halstenberg, a 34-year-old contract delivery driver from Norco, was arrested Tuesday, on suspicion of starting the fire, which burned thousands of acres in L.A. and San Bernardino counties.

San Bernardino County Sheriff Shannon Dicus said Halstenberg is suspected of intentionally setting the fire, and that investigators were looking into the possibility that he may be responsible for setting others. The sheriff said automatic license plate readers captured a license plate of a vehicle connected to Halstenberg near where the Line Fire began.

Dicus declined to say exactly how the fire was set, noting the investigation is in its early stages.

Halstenberg is expected to appear in court Friday.

Park Fire — Ronnie Dean Stout II, 42, was arrested on suspicion of arson in connection with the massive blaze that started near Chico.

Cal Fire said a man they identified as Stout was seen pushing a car that was already on fire into a gully in an area called Alligator Hole. The car went 60 feet down an embankment, spreading flames that eventually burned more than 400,000 acres and destroyed more than 700 structures.

Stout has pleaded not guilty and has denied pushing the car — he said it rolled — down the hill, according to The Sacramento Bee.

El Dorado fire — A San Bernardino couple who set off pyrotechnics during a gender-reveal party in 2020 and inadvertently ignited the blaze that turned into the 22,000-acre El Dorado fire were sentenced in February.

The fire killed a U.S. Forest Service firefighter and injured others. Five homes were destroyed.

Refugio Manuel Jimenez Jr. pleaded guilty to involuntary manslaughter and was sentenced to a year in county jail and placed on probation for a term of two years. He was also ordered to do community service, according to the L.A. Times.

Angelina Jimenez pleaded guilty to three misdemeanor counts of recklessly causing a fire to another’s property and was placed on probation for a year. She, too, was ordered to complete community service.

Where can I find wildfire resources?

Check our more wildfire coverage from the LAist newsroom.

• Listen to The Big Burn, our podcast that will get you motivated to get ready
• Wildfires are getting worse. What you need to know
• Every day is now fire season. Let's get you ready for the next wildfire burning near you
• Evacuation terms can be confusing. Here’s what they mean and how to sign up for alerts
• How to keep yourself safe from wildfire smoke
• This is why fire officials don't want you to stay and defend your home
• What does 'containment' of a fire mean, exactly
• What to do — and not do — when you get home after a wildfire
• If you want to help fire victims, resist the urge to volunteer