A growing number of wildfires in California have a common back-story: People caused them.

LOS ANGELES — Embers drifting from a campfire in a canyon ignite a blaze that incinerates 53 homes in Malibu.

A man driving on a dirt road in a forest stops on a swath of dry grass, and the hot engine kindles a wildfire that burns thousands of acres.

And a fire that destroys 78 homes in the Santa Barbara area is believed to have been caused by sparks from a power tool being used to clear brush.

A growing number of wildfires in California have a common back-story: People caused them.

Government statistics show that people were faulted for 5,208 wildfires in Southern California in 2008, the highest number since at least 2001. Between 2006 and 2008, Southern California was the only region of the U.S. to see a significant jump in the number of wildfires blamed on people.

Among the explanations given by experts: a three-year-old dry spell in California, the building of homes deeper and deeper into the backcountry, and perhaps better investigation and reporting of fires.

"As the drought continues in California, there are going to be more human-caused fires," said Don Smurthwaite, a spokesman for the National Interagency Fire Center in Idaho. "You can see the spread of development in virtually every area of the West," he added. "More people is always going to equate to more fires."

Nationally, about 70,000 wildfires in 2008 were attributed to human causes — a thoughtlessly flicked cigarette, a campfire left smoldering, a fallen power line, and sometimes, outright arson. That's about the same number as in 2001, although the figures fluctuate from year to year. The peak since 2001 was 80,220 wildfires in 2006.

In Southern California, the number of wildfires caused by people was about flat — roughly 4,000 — between 2001 and 2005. It dipped to 3,200 in 2006. Then, those figures increased sharply, to 5,140 in 2007 and 5,208 in 2008. Nationally, the number of wildfires attributed to human causes dropped in 2007 and 2008.

Lightning accounts for far fewer wildfires than people do — about 8,800 blazes across the nation in 2008. In Southern California, the number of wildfires blamed on lightning dropped from 409 in 2006 to 291 in 2007 and 174 last year.

The U.S. Forest Service alone recorded nearly 400 arson wildfires in California since 2005, but only a small number of them lead to criminal or civil cases. Prosecutors have wide discretion.

A pipe grinder who accidentally started a 38-square-mile wildfire in Santa Barbara County in 2007 that injured 40 people initially faced felony counts, but those charges were dismissed. He pleaded no contest to a misdemeanor charge of negligently setting a fire and was fined $200.

Earlier this week, a man was sentenced to 16 years in prison after pleading no contest to arson. He was accused of setting a series of fires in Los Angeles' sprawling Griffith Park last year.

"Two things are important for prosecutors to look at. One is the intent ... but on the other hand, there is the harm," said Michael Hestrin, a prosecutor in Riverside County. "It's a judgment call. No two cases are the same."