How Much Fuel Does A Green Spring Add To The Fire?

3:19 minutes

The Thomas Fire. Credit: Stuart Palley for the U.S. Forest Service/flickr

state of science iconThis segment is part of The State of Science, a series featuring science stories from public radio stations across the United States. A version of this story, by Jacob Margolis, originally appeared on Elemental.

We’re free of drought conditions.

We got to see some epic super blooms.

Our hills have been covered in lush green plants for months.

But then there’s the not-so-silver lining: we may be primed to burn.

For now, things look good, said Jessica Gardetto, spokesperson for the National Interagency Fire Center. With moisture levels still high, there’s not a huge risk of fires igniting and growing out of control.

But the rains will inevitably end.

“That risk,” she said, “is going to increase when all these grasses and fuels dry out and become ready to burn.”

The last time we had similar conditions was in the spring of 2017.

“I don’t remember it being quite as lush as this year with either the flowers or the vegetation, but it was plenty green and it was just so nice to see things starting to recover,” said Ojai resident Karin Dron, sitting on the porch of her stone house.

Surrounded by bright green grass on all sides, there is little evidence — besides a few blackened trees — that one of the worst fires in state history tore through her yard just a few years ago.

2017: A Perfect Year For Fire

“Extra precipitation in winter 2016 to 2017 helped to grow a bunch of new fuel,” said Park Williams, bio-climatologist at Columbia’s Lamont-Doherty Earth Observatory.

“On top of there being a whole bunch of new growth … the summer of 2017 was record-breaking, or near-record-breaking, across essentially all of the western United States, in terms of temperature.”

Which meant that abundance of new growth dried out quickly and, because of a delayed rainy season, stayed dry.

Grasses were the first to lose their moisture, followed by shrubs and old growth chapparal that had gone unburned for a long time and survived years of low precipitation during the drought.

That created ideal conditions for a big fire.

The Thomas Fire was sparked by SoCal Edison’s power lines and then fueled by Santa Ana winds (which peak in fall and winter).

Karin Dron watched as it consumed nearly her entire property, sparing only the home that had been there since the 1930s.

“There were a lineup of ten firetrucks on my driveway, which is about a quarter of a mile, and they were watching it burn,” she said.

More than 281 thousand acres burned and 10,000 structures were destroyed.

2019: It’s Going to Burn, Right?

On a recent trip into the San Gabriel Mountains, patrol captain Alberto Ortega took samples of shrubs to measure moisture levels, something that he now has to do year-round.

For now, they are moist.

But it won’t last. Plants are going to dry. How quickly that happens depends on how hot things get this spring and summer. And how long they stay dry depends on when our rainy season shows up.

“This is going to help us, basically at least at the beginning of the year,” Ortega said, explaining that higher moisture levels make it easier to extinguish fires when they start.

“Our fire season started extending longer and longer,” he said. “And we needed that fuel moisture sample for us to fight fire. You probably can see in the last 10-15 years, things are changing with the plants.”

Is This Climate Change?

As climate change progresses, temperatures will continue to rise, meaning greater rates of evapotranspiration that will cause plants to dry out faster.

“I think maybe the entire stretch from 2012 to 2017 could be seen as a harbinger,” said Williams, who’s written extensively about climate change on the west coast.

We could also see an increased variability in rainfall, meaning that rain could come in short intense bursts followed by long periods of dryness. That matters because when we miss out on deep sustained soakings during our wet season, recovery from dry periods is more difficult.

Another concern: indications that that the rainy season could keep showing up late.

It’s unclear how the Santa Ana winds will be impacted, though they’re not expected to worsen.

“Warming has been so extreme in California over the last century that every summer is hot and dry enough to support fire, no matter how wet this past winter was,” said Williams.

California has had a major wildfire every year for the past seven years, and the past five summers have been the warmest on record.

It’s Always Fire Season

Regardless of what happens, Dron always has fire in the back of her mind.

She lost four buildings on her Ojai property during the Thomas Fire.

We are on her porch, overlooking the Ojai valley below. There is no sign of a burned-out moonscape. Thanks to the rain, we are surrounded instead, by tall, beautiful, green grasses.

“It is gorgeous and we’re loving this spring. It’s certainly a super bloom and the wildflowers are great,” she said. “But yes, we’re probably going to have to do multiple fire clearances and we’re going to have to keep doing it … and it’s a little worrisome. That’s all I can say. We really don’t know what’s coming.”

Segment Guests

Jacob Margolis

Jacob Margolis is a science reporter and host of “The Big One: Your Survival Guide” podcast at KPCC in Pasadena, California.

Segment Transcript

IRA FLATOW: Now it’s time to check in on the state of science. 

SPEAKER: This is KER– for WWNL– St. Louis Public Radio– Iowa Public News. 

IRA FLATOW: Local science stories of national significance. California had a very green spring. The hills are alive with color. Residents are certainly thankful for the vegetation that springtime rain has brought. 

But they may be sorry come next wildfire season when those verdant tales once again turn into kindling. That is, how much fuel does a super green spring eventually add to the fire? Jacob Margolis, science reporter at KPCC, set out to try and answer that very question. Hi, Jacob. 


IRA FLATOW: So this is quite interesting. We’ve talked before about a strong rainy season in California. Does it offer protection against a bad wildfire season? We found that maybe it does not. 

JACOB MARGOLIS: Yeah, so we want a lot of rain, right? We want our reservoirs to fill up. And with a lot of rain, those landscapes that really dried out, especially during that drought, they start to recover, especially the bigger fuels. 

The bad news is that, as you said, along with all that rain comes the growth of really fast-growing fuels like grasses. And those actually dry out very quickly. They’re ready to burn. They’re good fuels to burn. They burn hot, and they burn fast. 

IRA FLATOW: And there’s even differences in Northern California versus Southern California, right? 

JACOB MARGOLIS: Oh my god, it’s hugely diverse here. And in Northern California they have to worry about the grasses too. But grasses aren’t enough on their own to fuel huge wildland fires. You need bigger fuels. 

So in Northern California, the big concern are the large swaths of dead trees that they have. And the fire is really hard to fight when those grasses catch. The trees eventually catch on fire. And that fire travels across the top of the trees. Firefighters have told me it’s pretty tough to fight. 

Here in Southern California it’s a bit different though. Our bigger fuel concern is largely with chaparral and brush, so lower lying plants. And those naturally swing back and forth between moist and dry. 

The thing is, since we’re coming off all these drought years with only a couple of wet years in between, it means that any of that recovery that we had that could possibly lower the fire risk, it could possibly go away. I called the National Interagency Fire Center and spoke to Jessica Gardetto, a spokesperson there. And this is what she told me. 

JESSICA GARDETTO: I do know that, overall, the vegetation in Southern California has recovered because of this moisture. But one good year of rain does not basically erase years of drought. So if we do get those high increased temperatures for a long period of time, without rain to mitigate them, those fuels such as chaparral could dry out and be ready to burn. 

IRA FLATOW: So Jacob, do firefighters know which areas will be vulnerable based on the vegetation that grew this spring? 

JACOB MARGOLIS: Yeah. They don’t necessarily– I mean, they’re watching everywhere, first off. But second, they don’t necessarily– there are certain areas that are more susceptible. And those are going to be the areas that have had a lot of old growth that’s been around for a long time that hasn’t burned because of fire management practices, or maybe just a fire hasn’t started around in that place. That’s what happened with the Thomas Fire in 2017, which was, at the time, the largest fire in state history. 

IRA FLATOW: All right. We’ll just have to watch and wait and have you back, Jacob. Jacob Margolis, science reporter and host of the podcast The Big One, Your Survival Guide from KPCC.

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