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Breaking down the myth of California's fire season

Marti Witter points out plant life to A Martinez at Wild Walnut Park in Calabasas.
Marti Witter points out plant life to A Martinez at Wild Walnut Park in Calabasas.
KPCC/Lori Galarreta

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Out on the corner of Old Topanga Canyon Road and Mulholland Highway in the Santa Monica Mountains is a little place called Wild Walnut Park.

The park is named, naturally, for the walnut trees that dot the landscape. There's not a lot of greenery otherwise, just tall wheat-like grass and many dirt trails.

Those trees give off the only shade available – and it is hot. A Martinez and the Take Two team know this firsthand, because we visited the park right in the middle of the June heatwave.

That's where we met Marti Witter, an ecologist with the National Park Service. She described what this place used to be like:

"So, this is an area that previously had sort of low-growing coastal sage scrub with really beautiful gray leaves of purple sage and California sage."

That was before a 500-acre fire destroyed all of it about a year ago.

"What we're seeing now is not the happy picture we would usually expect to see after a fire in chaparral and coastal sage scrub."

Wild Walnut Park in Calabasas on June 19, 2017.
Wild Walnut Park in Calabasas on June 19, 2017.
KPCC/Lori Galarreta

It should all be growing back now, but it's taking longer than expected.  That's because the fire blazed in the middle of California's drought, before the wet winter came and quenched the state's thirst. But the rain is what brought us to the park.

We wanted to know how all that water could affect the frequency and the intensity of fires this season. 

How much of a role does rainfall play in California's fire ecology?

"Rainfall has a lot to do with our fire ecology. For example, four years of no rain has had a terrible effect in terms of just generating huge amounts of standing dead fuels that are not normally there. 

Another really important effect is the timing of rainfall. So, we get our rain in the winter but if our rainfall comes heavily in November and December and then stops early, it means our potential to have fires earlier starts. And that's one of the things when people talk about climate change increasing the amount of climatic variability, that's probably one of the effects we're going to see... Is that we're going to have a larger window when fires can occur."

The two Californias

"We talk about California as having two different fire regimes. There's coastal and Southern California, which would naturally have low frequency of fires. Maybe every 50 to 70 years. They burn very intensely... So it's perfectly natural after a chaparral or a coastal sage scrub fire, to see all of the vegetation burned off and see the black destroyed landscape. But those landscapes are adapted to come back after fire.

The forested systems are different. That's the other California. So, instead of having this infrequent fire regime, they actually have a regime of frequent low-intensity fires. But those fires are actually pretty easy to put out, so they're slow moving, ground surface fires. But the factors that control fires in Southern California and in the Sierra Nevada or in our Southern California upper elevations, are different.

First of all, you have the potential for lightning ignited fires, which was the natural source of fires in those habitats. And also down, coastal Southern California has one of the lowest lightning ignitions."

Fires that happen here can often be triggered by power lines coming down in high winds, cars pulling off into herbaceous growth by the side of the road, etc.

A portion of Wild Walnut Park that is having trouble recovering from the 2016 fire.
A portion of Wild Walnut Park that is having trouble recovering from the 2016 fire.
KPCC/Lori Galarreta

The fire season myth

"We can have a fire at any time. But I think we really have fires under certain climatic conditions. So, you're going to get larger serious fires under specific climatic conditions and those do not occur 12 months out of the year. So, I think people should be careful when they talk about the year-long fire season.

 In fact, it's year-long in the sense that we can get ignitions and if we didn't have this quite amazing fire response capacity then it would be more serious. But in Southern California, you have massive response to fires. So, you want to have that capacity 12 months out of the year, but you're not going to see vast amounts of land burned all through the year. It's going to be tied to seasons where these climatic conditions are conducive to large fires."

To listen to the full segment, click the blue play button above.

Special coverage: California's fire risk

This story is part of a full day of special coverage examining the summer fire season following this winter’s record rain and snow. Check out the rest of our coverage below:

Sierra fire risk: One place we looked is a favorite vacation spot for Southern Californians this time of year — the Sierra Nevada. KPCC’s Emily Guerin has more.

Erskine Fire: We checked in with the Kern County town devastated by one of last year’s most destructive wildfires. The Erskine Fire burned more than 280 homes, left two people dead and displaced hundreds. As KPCC’s Sharon McNary reports, it’s been a slow and difficult return to normal for many.