Two Fire Experts Give a 100-Year Local Fire History

USGS scientist Jon E. Keeley (left) and Pulitzer Prize winning journalist Bettina Boxall

Studying history is typically a method to avoid future mistakes.  An audience of 100 was recently treated to a presentation entitled “100 Years of Fire in the Santa Monica Mountains.” The crowd attending was eager to learn about traits of local fires during the past century and how they might protect themselves when the next blaze strikes.

Pulitzer Prize winning journalist Bettina Boxall opened the evening at the Pacific Palisades Theater last week by recalling her first experience with brush fire in 1993. 

“It ran from the San Fernando Valley to Malibu in an afternoon and I will always remember that,” she said of its swiftness.

Boxall, who’s been covering wildfires for the LA Times ever since, gave her expert opinions on wildfire characteristics and strategies along with Jon E. Keeley, a research scientist with the United States Geological Survey.

The two speakers pointed out the increase in blazes in the past 100 years and the differing factors that drive fires from Northern to Southern California.

The two halves of the state differ in that the northern areas are blanketed by forest with many blazes ignited by lightning strikes. Southern California—especially the Santa Monica Mountains—is overlaid with chaparral and coastal sage brush ecosystems that carve out its many canyons. Southern California fires behave differently than forest fires because those chaparral-covered canyons create wind tunnels during Santa Ana conditions and Southern California fires are on the rise.

“We’re seeing a change in California. Since 2000, there’s been a doubling of the amount of area burned relative to the prior two decades,” according to Keeley.

Of course, we have all heard about climate change and global warming, but Keeley blames the increase in fires on increasing human development. 

“Since 2000, we’ve added six million more people to the state and every year we’re adding 300,000 more people,” Keeley described. “We’re populating the landscape that increases the probability of someone starting a fire during a Santa Ana wind and an increase in population means the spread of urban sprawl into new landscapes.”

After that sobering warning, Keeley went on to describe the damage to landscapes and ecosystems after brushfires. The scientist described what happened in Malibu in the spring of 2019 when hillsides destroyed by the Woolsey Fire erupted with one of the most spectacular wildflower seasons ever. Even though the landscape had been devastated, typically the first spring after a blaze finds a rebirth in greenery due to the coevolutionary history between flora and fire. Resilient common shrubs can resprout with normal growth or seedlings. Some have dormant seeds that can sit for years under the soil and are stimulated to germinate by a fire. California lilac or ceanothus that blankets our local hillsides have underground seeds that are triggered to germinate after a blaze. Some species’ seeds can lay dormant for more than a century. They require smoke to trigger germination.  After a few years, many chaparral sites can recover. 

“Not only is chaparral adaptive to these fires, but it’s dependent,” Keeley stated. However, the ecosystem is very sensitive to the interval between fires. Too many fires can mean trouble.

“Historically, in the Santa Monica Mountains, fires burned much less frequently, but with the growth of the human population in the area comes the frequency of brush fires because 99 percent of all fires are started by humans,” according to Keeley. “What happens when you increase that frequency—a fire more than every 30 years—is, basically, most of the species are extricated. Mostly what you have is exotic grasslands.  These are not native species. They come in. They have a lot of impact on our natural resources.” 

Invasion of non-native species such as the black mustard grass now seen throughout Malibu after the Woolsey Fire impacts the hydrology of the landscape and later becomes flammable. Native shrubs can hold water on steep slopes much better than shallow-rooted grasses. Fire regime is impacted, too, as some native species are only flammable six months during a year and some new grasses are flammable 12 months out of a year—meaning the “superbloom” of last year can serve as kindling for the next blaze.