Quick Take
To a large degree, the redwood forests of the Santa Cruz Mountains have survived and are thriving in the wake of 2020's CZU fire. We vulnerable humans often take comfort in the power of ecosystems to adapt and survive. But, scientists believe, we should probably stop short before declaring that all is fine in the world of California’s redwoods.
It was an eon ago. It was the day before yesterday.
It belongs to another era in history. It is our current new reality.
The historic trauma of 2020 (one among many, in hindsight) that Santa Cruz County locals call simply “CZU” really does a stress test on the mental and emotional perception of time. Depending on your personal experience of the catastrophe that started with a freak lightning storm on Aug. 16, 2020, CZU might feel for you like a surreal dream or a fresh wound, or something that constantly oscillates between the two.
Then again, you’re not a redwood tree.
In reflecting on the fifth anniversary of the CZU fires — which burned more than 86,000 acres in Santa Cruz County and destroyed more than 1,400 houses and other structures — it might make sense that to learn something of the human experience of the fires, we start by looking at the non-human realm. Where are we, five years later, in the natural world? What’s going on in Big Basin?
The CZU fires torched a whopping 97% of Big Basin Redwoods State Park, consuming all of its buildings and man-made structures. Five years later, it doesn’t take the sharp eye of a naturalist to find evidence of CZU burn scars at Big Basin. Such evidence is everywhere. But fire, even catastrophic fire, means something different in forests like this one.
Anyone who has grown up on the California coast, or lived here a long time, has doubtlessly heard about the resilience of Sequoia sempervirens, aka the coast redwood, when it comes to fire. CZU is providing an uncomfortably close illustration of the enduring superpower of redwoods.
A tale of two forests
Like many, I remember pre-CZU Big Basin and the thick canopy of foliage 200 feet high that created the shady, often spacious understory amid the redwoods. I also visited when the park was first reopened after the fire, in the summer of 2022, and saw charred black and ashy gray where I once saw only green and brown. State parks officials who were on site even sooner after the fire remember an unrecognizable landscape of smoldering ruin where the air itself felt burnt.
Today, there’s a different vibe at Big Basin. It has not returned to its 2019 state, but there are signs everywhere that it’s headed in that direction. Perhaps the most significant loss, from the standpoint of biodiversity, was the redwood canopy itself. Without the canopy, sunlight reaches the ground where it never could before, creating opportunities for other tree and shrub species to proliferate, and to create a different kind of forest.
Environmental scientist Tim Hyland, a natural resources program manager for California State Parks, likes to tell the story of Big Basin in comparison to another nearby state park, Butano State Park, just to the north in San Mateo County.
“Big Basin burned at high severity over a short period of time,” said Hyland at his office at Henry Cowell Redwoods State Park in Felton. “So, the effects from the fire were significantly different there than [in Butano].”
As the fires spread, firefighting efforts were largely concentrated in protecting the communities of the San Lorenzo Valley, leaving Butano largely to burn.
“And in Butano,” said Hyland, “it moved very slowly with very low intensity, burning through that park in a way that was actually, ecologically, very beneficial.”
Hyland is uncomfortable with the word “unprecedented” in relation to CZU in Big Basin. “There’s good evidence to show that these forests have burned at high severity in the past, even if that’s not typical,” he said. “More typically — and all of the studies of fire frequency and fire severity in the Santa Cruz Mountains [affirm] — are relatively small, low-intensity fires that happen relatively frequently, between seven and 12 years.”
In Butano, the redwood canopy was, more or less, spared from the fires, which mostly burned fuel on the ground that had been accumulating in large part because of 150 years of fire-suppression policies. In a purely ecological sense, low-intensity fires of this kind are simply part of the local climate. In this part of the world, fires do what decomposition does in other places. Or, to put it in Silicon Valley parlance, fires are not a bug in the system but a feature.
“We live in a Mediterranean climate,” said Hyland, “which means cool, wet winters and warm, dry summers. So, when do things rot? When it’s warm and wet, and it’s almost never warm and wet here. So nutrients get recycled by fire.”
No one is used to talking about CZU in any other terms than tragedy, which undeniably it was for many. But in a more big-picture perspective, at least in terms of forest ecology, the fires might have been a boon, at least in Butano.
Big Basin was, of course, a different story. The high-intensity fires that turned Big Basin’s lush green into grayscale eventually turned into low-intensity fires that lingered for months. Hyland said that a 100-acre fire that erupted in Big Basin a year after CZU was in fact the long tail of the original fires a year earlier.
“In the relatively mild winter after CZU,” he said, “there were still fires in the tops of some of those trees. One of the Cal Fire captains told me you could hear the results of this. The trees were just blowing up because there was so much heat it turned all the water in these trees to steam, and that just blew the top off of them.”
A walk among the Dr. Seuss trees
On a warm summer weekday, I took a walk through Big Basin with senior park aide Joanna Ferraro. Like many ecologically minded people, Ferraro seemed to be studiously avoiding value judgments when it comes to the forest pre- and post-CZU, largely because it doesn’t make sense for a scientist to say that one evolutionary stage of the forest is better or worse than another one. Still, I asked her about the experience of being in Big Basin before CZU, and she grew nostalgic for duff, the organic matter that usually covers the ground in redwood forests.
“Very similar to Henry Cowell,” she said, “the whole ground was that nice, burnt-orange, of all these fallen needles and the soft duff, so you have this golden, sepia-toned walk.”
Today, the fire-induced opening of the canopy has produced an explosion of other plants growing where they would not grow before. Ferraro pointed out several examples of ceanothus, also known as California lilac, that is called “fire-following.” The California lilac will spread its seeds in the duff of the forest floor, but those seeds do not germinate until they detect heat strong enough to suggest a high-intensity fire that might open up the canopy to allow them the sunshine they need to grow.
“It’s amazing that this plant in particular,” said Ferraro pointing to a ceanothus shrub, “is adapted to only get triggered by intense heat, and all these seeds that have been dormant for a hundred years are suddenly, poof, this is their time.”
The presence of ceanothus then gives the naturalist clues about fire in the history of any given stand of redwoods. Ceanothus, in fact, can quickly develop a kind of monoculture in severely burned areas, sometimes to the detriment of other plants that might have a chance in a suddenly open spot under the canopy.
“But,” said Ferraro, “ceanothus provides for native pollinators. It’s food for deer. It has its place.”
As for the trees themselves, they have a remarkable capacity for maintaining a kind of pilot light of life even in the face of desolation. A burned-out husk of a tree trunk will eventually be covered in green shoots. Big Basin today, five years after the fires, is rife with these kinds of trees which Ferraro playfully referred to as “Dr. Seuss trees,” towering trunks covered in green, as if wearing a sweater.
She then coaxed me to do something that I don’t think I’ve ever done in a redwood forest: eat. She found a berry bush which she identified as huckleberry. We tasted the sweet, blueberry-esque berries, another of the adaptations of a post-fire landscape.
Big Basin is also providing illustrations of how other species of trees, namely tan oak and Douglas fir, adapt to fire, and their differences with the coast redwood. The firs, for instance, are nearly as resilient as the redwoods and CZU killed many of them. At the same time, an open canopy has allowed seedlings to sprout to create a new generation of Douglas firs. Other shrubs and small trees, like coyote bush and manzanita, are also getting a foothold.
But even this environment, five years after a giant fire, is temporary. As the trees grow stronger, the canopy will again close up and sunlight will again become a precious commodity on the ground. Ceanothus and other species will die away, creating fuel for the next fire. In fact, Big Basin has a program in which volunteers are gathered to create fire piles to help keep the fuel loads manageable.
To a large degree, the redwood forests of the Santa Cruz Mountains have survived and are thriving in the wake of CZU. We vulnerable humans often take comfort in the power of ecosystems to adapt and survive. But, scientists believe, we should probably stop short before declaring that all is fine in the world of California’s redwoods.
“The redwoods are adapted to high-frequency, low-intensity fires,” said ecologist Tim Hyland. “They’re also adapted to infrequent high-intensity fires. What they are not adapted to are high-frequency, high-intensity fires. This is a real concern. We want to do what we can to mitigate the disaster that is sure to come. If we want to keep our redwoods here, which I think we do, then [a big fire] is something we want to avoid.”
At least, for the next 10 years?
Hyland nodded. “I’d give them another 20.”
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