Misconceptions About Big Basin State Park CZU Blaze

On August 16, 2020 record  heat spread across California. In Death Valley the temperate reached 130 degrees. But even places on the coast, normally cool due to off shore currents, reached records seldom seen. In Santa Cruz, on Monterey Bay, the temperature rose for two days  to 107 degrees.

All the blackened giant old growth redwoods in this photo, some up to 2000 years old, survived the CZU fire and are now sprouting branches in their treetops. Photo George Wuerthner

The rising temperatures gave rise to 12,000 thousand of lightning strikes that started 580 fires across the state,  including some that struck the Santa Cruz Mountains in Big Basin State Park. The lighting ignited  the CZU blaze which raced through 2000-year-old redwoods. Firefighters said they encountered conditions they have never seen in coastal mountains before.

Ultimately the wildfire charred 86,509 acres and was contained on September 22 but not fully controlled until December 23rd.

Nearly all the mature trees survived the high severity fire, and are now sprouting branches. Photo George Wuerthner

The fires destroyed 1,490 buildings in the San Lorenzo Valley and surrounding hills including the Visitor Center at the park.  The fire burned 97% of the park, “devastating the ecosystems” of California’s oldest State Park.

Dense redwood seedling cover the ground throughout the CZU burn area. Photo George Wuerthner

Two years after the fire, a paper by the California Fish and Wildlife suggested that such high severity blazes like the CZU wildfire were destructive when the authors declared: “from the local historical context, prior to 2020, fires in and around BBRSP would rarely burn at high severity, compared specifically to the CZU fire (SCMBC 2022). Seldom would fires burn into the redwood and Douglas-fir tree stands of BBRSP and up into their crowns (Brown and Baxter 2003). Low intensity fires can blacken the thick outer bark of old-growth conifer trees, but not burn so hot as to kill them.”

Media outlets repeatedly proclaimed that the fire had “destroyed” the old growth redwoods, and the “disaster” would take decades for the forest to “recover.  Such pronouncements are typical after any major fire, and no doubt if you were to see Big Basin’s forest immediately after the blaze, it looked like an ecological “catastrophe.”

Mapping after the blaze showed that the wildfire severity classhttps://journal.wildlife.ca.gov/2023/04/12/impacts-of-the-czu-lightning-complex-fire-of-august-2020-on-the-forests-of-big-basin-redwoods-state-park/ as (light Green) low severity 2%, (yellow) moderate severity 20% (majority of live canopy cover lost), and (red) high severity 77% (all live canopy cover lost).


However, while wildfire can “destroy” homes, in natural situations, fire transforms and reinvigorates ecosystems, and this is exactly what happened at Big Basin State Park.

I had a chance to visit Big Basin State Park and what I saw was anything but “devastation”. According to a ranger I spoke with nearly all the mature trees survived the fire and were pushing out new branches from epicormic buds. These trees looked like narrow brushes due to the tight grow of new branches that radiated out from the trunks of burnt trees.

The epicormic buds in older trees sprout new branches giving the trees a bottle brush appearance. Photo George Wuerthner

Epicormic buds lie dormant in redwood trees, waiting for release by some natural event such as insect attack or wildfire.

The epicormis buds are seen in this cross section. They can remain dormant for decades, and sprout when a tree is burned. Photo George Wuerthner

The fire stimulated an amazing amount regrowth including redwood seedlings, plus tan oak, ceanothus, madrone,  Douglas fir, and even a few knobcone pine seedlings. Though it was only three years since the burn, the ground cover vegetation was over 10-15 feet tall in many areas. It would be impossible to negotiate the woods now without a trail.

Tan oak seedling are abundant after the blaze. Photo George Wuerthner

The problem in perception is partially due to our spatial and temporal perspective. There has not been a large hot fire in the Santa Cruz Mountains in many decades, perhaps centuries, but such blazes, from the perspective of a tree that can live 2000 years is not aberrant.

One has to ask why didn’t Big Basin burn up prior to 2020. Was there really that much less fuel in 2021 or 2010? Or was the main factor responsible for the CZU fire the unusual climate/weather conditions of extreme drought, high temperatures, low humidity, and high winds?


The most common explanation for the high severity CZU blaze is fire suppression-lack of Indian burning.

I heard from this explanation from park rangers and read similar ideas in numerous articles describing the fire. According to this perspective, past Indian cultural burns kept fuel levels low and such high severity blazes didn’t occur. But because of fire suppression, and suppression of Indian fire on the landscape, we now have large blazes.

This is the most popular rationale used by the timber companies, federal and state agencies and tribal people to justify forest manipulation including prescribed burning and thinning (logging) across the West. One is left with the impression (done on purpose) that without human intervention, our plant communities would be a mess—and of course, be “destroyed” by high severity blazes.

For instance, in a TV story after the CZU blaze, Sarah Bath, Executive Director of the Sempervirens Fund echo the common refrain that Indian wisdom kept the forests from burning at high severity. Bath said:  “The way that state parks have interacted with fire up until pretty recently has largely ignored Indigenous knowledge,” Barth said, referring to the annual controlled burns by Native American tribes, which are an ancient, effective practice of fire management that cleared out underbrush and encouraged new plant growth. But she also said she’s heartened by how state parks in this region have been “very receptive to that kind of partnership” with Indigenous communities when it comes to managing fire.”

Note this narrative naturally leads to justifications for human intervention and manipulation of plant communities.

Black oak in autumn and Half Dome, Yosemite Valley, Yosemite NP, CA. Places like the Yosmite Valley where Indians occupied villages likely had more frequent localized fire, but the Yosemite National Park landscape was largely influenced by climatic conditions, not human ignitions. George Wuerthner

However, the bulk of scientific research suggests that while cultural burning may have had limited influence on small areas of the forest, from a landscape evolutionary perspective it was insignificant.


Coast redwood evolved 65 million years ago. Humans only colonized North America 15,000 or so years ago. For most of their evolutionary history, they existed without human manipulation. They do not need humans to be healthy or resislent. They do just fine on their own. Photo George Wuerthner

The coast redwood evolved as a separate species as long ago as 65 million years ago.  Humans only colonized North America within the past 15-20,000 years, depending on whose research you choose to believe. That redwood existed for millions of years without human intervention suggests they do not require “active management.” The human arrogance of such assertions demonstrates the anthropogenic perspective that has come to dominate the environmental movement in recent years.

Chaparrel along Trinity River, CA. Chaprrel cannot tolerate frequent fire–evolutionary evident that Indian burning did not alter extensive areas of the landscape. Photo George Wuerthner

We have many examples of plant communities that dot California and the rest of the West which do not tolerate frequent, low severity burning. Chaparrel is the most extensive plant community in California that cannot survive if burned at frequent intervals. The presence of chaparrel throughout the state is clear evolutionary evidence that Indian burning did not modify plant communities at a landscape scale.

Further evolutionary evidence has to do with epicormic buds. if Indian burning always kept fuels load so that large high severity blazes did not occur, why would redwoods “invest” in epicormic buds?

Dense foret regeneration as a consequence of high severity burn. Photo George Wuerthner

I’ve addressed this issue in the past, and the scientific evidence suggests that climate, not human ignitions, and fuel loads, controls the size and severity of wildfires. The amount of the landscape that tribal cultural burns influence has usually been small and localized.

Under climate conditions that drove the CZU blaze that consisted of high temperatures (like 107 degrees recorded in Santa Cruz when the fires began) combined with excessive drought (CA was experiencing a severe drought that hadn’t been recorded in a thousand years) along with low humidity and high winds, you get the rare, but episodic large fires.

Under such conditions, wildfires blow right over and through “fuel reductions” whether due to thinning or prescribed burning. Indeed, in some instances, these practices can exacerbate fire spread by opening the forest canopy to more sunlight, soil drying and wind penetration. And both logging and prescribed burns can promote the growth of “fine fuels” like grass, shrubs, and other small easily ignited vegetation that is the main factor in fire spread.

Epicormic buds sprout new branches on severely burned redwood trees, evidence that these forests have regularly expeienced high severity blazes throughout their evolutionary history. Photo George Wuerthner

 The fact that redwoods possess epicormic buds which is an evolutionary response to wildfire demonstrates that such hot high severity fires are not “abnormal” or “destroy” the trees. Rather it shows that episodic fires such as the CZU blaze are quite normal in redwood forests. The presence of other vegetation like knobcone pine whose cones typically open after a major fire, and the sprouting behavior of redwood stumps are also evidence that high severity fires were always a part of the redwood forest ecosystem.

Nevertheless despite the obvious conclusion that redwood forests are perfectly capable of surviving without human manipulation, most people including Save the Redwood League cannot stand to leave Nature alone.

Even if the blaze had resulted in significant redwood mortality, the resulting snag forests still have an important role to play in ecosystems. Numerous species of plants and animals rely on dead trees for their own survival, whether that is cavity nesting birds, fungi that live on the trees, or the small mammals that may live under or within down wood.

I encourage anyone who thinks that high severity blazes “devastate” ecosystems to visit Big Basin State Park to see how wildfire creates ecological opportunities and serves to sustain, not destroy, these landscapes. And hopefully with greater understanding of fire and evolutionary responses of plants, one can begin questioning the myth that our forests “need” human management to be “healthy” and “resilient.”


  1. Wayne Tyson Avatar
    Wayne Tyson

    Context is in a constant “state” of change.


George Wuerthner is an ecologist and writer who has published 38 books on various topics related to environmental and natural history. He has visited over 400 designated wilderness areas and over 200 national park units.

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George Wuerthner