Alien Shrubs From Mars?

In Pursuit of Logic: Part II of V

Continuing our description of conversations we’ve had recently concerning chaparral, fire, and illogical thinking, Part II of our series shares an often-encountered opinion that in someway, somehow, one of our favorite chaparral shrubs is an unnatural, alien invader. In this case, hoary leaved ceanothus (Ceanothus crassifolius).

With pretty white blossoms and gnarly leaves with fuzzy undersides, this chaparral shrub can be found in large stands decorating foothill areas from San Diego to Santa Barbara.

Hoary leaved ceanothus in bloom.

The Invasion of the Alien Brush!

During a discussion about a proposed 30-35 mile long, 200-300 foot wide “fuel” break near San Rafael in Marin County at the base of Mt. Tamalpais, a renowned fire scientist suggested that a stand of ceanothus could be unnatural. And is often the case lately, his characterization was tied to the latest trend in promoting habitat clearance that we discussed in Part I of this series, past Native American fire use.

“Given that the area was likely burned frequently by First People, and if that was the case, then the greatest human impact on the ecosystems has been the lack of ecologically appropriate fire to sustain the post-Pleistocene landscape. When I was at the Fire Lab in Riverside, I occasionally asked the question regarding the baseline of consideration for what was a “native” condition. For example, from my limited understanding, an early Forest Reserve survey of Mt. Wilson (San Gabriel Mtns.) indicated significant oak-grass cover that is now largely Ceanothus crassifolius. Just a thought and curiosity regarding the Audubon and Native Plant Society concerns.”

This statement reveals several common themes in anti-chaparral chatter, shrub phobia and the pastoral bias favoring open grasslands.

How Did the Ceanothus Seeds Get There – Aliens from Mars?

Suggesting that ceanothus in the San Gabriel Mountains somehow replaced an historical oak/grassland due to the “lack of ecologically appropriate fire” demonstrates a serious misunderstanding of chaparral ecology.

C. crassifolius could not exist on a site that was not naturally characterized by infrequent, high-intensity fire.
Why? It’s a fascinating ecological story.

C. crassifolius is an obligate seeding species, meaning the species’ response to fire is the death of adult shrubs and the germination of their seed in the soil seed bank, in this case facilitated by heat (a pore in the seed coat is modified by heat, allowing water to enter, and thus stimulating the seed embryo to grow). Additional explanations (with photos) of this and other types of fire response chaparral plants have evolved can be found on our website here.
Under extreme, long-term drought conditions over many decades, C. crassifolius shrubs can die and disappear from a site. This is starting to happen now in the Santa Monica Mountains, featuring the characteristic curvy bundle of stems and twigs that dead ceanothus form – closing in on themselves as they sadly bid farewell to the world. The empty space left behind is usually filled in by other shrubs. However, the species still exists! Hiding in the soil seed bank are thousands of tiny seeds just waiting for a fire to kick them into action.The next high-intensity fire will cause an amazing population explosion of feisty, little ceanothus seedlings.

There is no other natural way for obligate seeding ceanothus to be present.

Dying ceanothus closing in on themselves as they sadly bid farewell to the world. This area had been type converted to weedy grassland prior to the last fire. These shrubs, when alive, were the last remnants of the original chaparral stand.

However, after thinking about this for awhile, I thought that maybe, just maybe there’s one unnatural, although highly unlikely, process that could explain how an area now dominated by C. crassifolius could have previously been a grassy oak woodland. The site could have been type-converted through the manual removal of native shrubs, then followed by severe overgrazing. Someone had to have planted a few oaks as well. At some point, the site was burned, allowing some C. crassifolius seedlings to germinate. We say some because grass fires burn at too low-intensity to do the job completely, as can be seen in the photo above.

The point to remember is that the only way a ceanothus seed bank could be present is if an area’s natural fire regime is one of infrequent, high-intensity fire – meaning the presence of C. crassifolius is the natural condition. So what is this “lack of ecologically appropriate fire” (i.e. human interference) postulated by the fire scientist? It could be an example of cognitive incompetence – the logically painful experience of trying explain away cognitive dissonance when data challenges one’s favored paradigm. You can read more about this in our chapter, High-Severity Fire in Chaparral – Cognitive Dissonance in the Shrublands.
An interesting story related to how natives can come rushing back to an area that has been ecologically compromised, concerns Catalina Island after the 2007 Island Fire. The place, previously dominated by non-natives, exploded with fire-cued native species that hadn’t been seen for more than a century. The native seed bank had been waiting patiently. It was the one chance the island had to restore its natural wonders.

Unfortunately, the presence of non-native deer and bison consumed every native seedling that emerged (the same pressures that had helped compromise the island in the first place). Politics prevented the control/removal of the hoofed locusts, as John Muir called sheep in the Sierra Nevada.

The island is back again being overwhelmed with non-native weeds and grasses, but this time without a realistic hope of ever being restored naturally. The native seed bank has been spent. As a testament to what could have been, a few areas were enclosed by fencing to protect the emerging natives plants from being grazed. The growth was phenomenal. From our understanding, though, the fencing has since been removed with expected consequences – the plants once protected were grazed out of existence.

Some areas after the Island Fire on Catalina were enclosed by fencing to keep the deer and buffalo out. You can see the difference when Nature is allowed to recover, and when non-native species (weeds, deer, buffalo) have free rein – an oasis of native life surrounded by a sea of chaos.

Anti-ceanothus myopia has also impacted Cuyamaca Rancho State Park in San Diego County. Managers there characterized stands of beautiful Ceanothus palmeri in the park, growing between trees and snags burned during the 2003 Cedar Fire, as an “unnatural invasion.” Over the past ten years, the park has engaged in an effort to cleanse portions of the park of the first stage of post-fire natural succession through mastication, herbicides, and prescribed fire – an effort they claim is necessary to bring the forest back. Most of the trees they planted died in their first and second attempts. The failure was predictable because ceanothus species provide shade for conifer saplings and restore nitrogen to the soil. In addition, heavy equipment compromised the soil’s important fungal network.

We don’t know if the millions of dollars of carbon credit dollars being dangled in front of California State Parks had anything to do with their effort to purge ceanothus from the park, but it has certainly paid for the crusade. The clearance damage has been so extensive that we avoid driving through the park these days.

Pastoral Bias

Our culture has historically loved pastures, open grasslands (and lawns). It’s where we grow our crops, graze our livestock, build our homes. Grassland is also a lot easier to walk through than chaparral. This bias probably has a behavioral genetic link as well – we likely evolved as a species while hunting and living on the savanna.
We’re not sure if the reference to the “oak-grass cover type” by the above-mentioned fire scientist is a mere reflection of a long-lost conversation, or is symptomatic of the inherent bias many people have for grasslands. But it does remind us of the continual arguments we have gotten ourselves into when encountering the claim, especially with folks in central and northern California, that where chaparral exists today was once native grassland. Meaning, chaparral has invaded the pasture. Such exaggeration and hostility towards native shrublands is as historic as the schism between northern and southern California. We discussed the desire to remove chaparral in favor of grasslands in a paper several years ago. Here’s a snip:

In a 1949 document on “brushland management” one author wrote, “Our real problems as far as range improvement in brush areas is concerned, are how to eliminate the brush from areas capable of producing appreciable quantities of forage, how to prevent the invasion of brush on our better range areas, and how to revegetate these areas with good forage plants…”

You can access the full paper here: Chaparral as a Natural Resource.
Don’t get us wrong, some of our friends are grass. Purple needlegrass (Stipa pulchra), California’s official state grass, is often found in open areas within both chaparral and coastal sage scrub (the fact that California doesn’t have an official state shrub does, however, speak volumes). But most “grasslands” these days are actually non-native weedlots, many of which (especially west of the coastal ranges) were once native shrubland communities that were eliminated by fire (beginning with Native American fire use), overgrazing, and/or the plow.

First People
Consider again the fire scientist’s comment about Indigenous fire use.

“Given that the area was likely burned frequently by First People, and if that was the case, then the greatest human impact on the ecosystems has been the lack of ecologically appropriate fire to sustain the post-Pleistocene landscape.”

The essence of this perspective is that Nature must be managed by humans, otherwise it is not ecologically appropriate. It also presupposes that the first humans to settle California thousands of years ago spent significant amounts of time lighting fires to create and sustain an artificial environment across tens of millions of acres, an artificial environment that was supposedly much improved over the natural one. This is one of the reasons the appropriation of Native American culture to promote habitat clearance through prescribed burning is such a threat. It threatens the idea of wilderness – the right of native plants and animals to be left alone.

One wonders how the natural environment, including ceanothus, evolved and thrived for millions of years without our help.

Dozens of Ceanothus tomentosus seedlings emerging between resprouting toyon, chamise, and mission manzanita.
A dense cluster of Ceanothus seedlings emerging from a rodent seed cache. Rodents play a crucial role in the distribution and germination of chaparral shrub species. Fellow Chaparralian Tom Parker has studied this interesting phenomenon. Here’s one of Tom’s papers explaining it all.
Ceanothus seedlings emerging in front of its burned, and expired, parent.
A Black-headed Grosbeak enjoying the post-fire Ceanothus blooms in the Sierra Nevada.

In Pursuit of Logic Part I: We’re Getting Indigenous Burning all Wrong

In Pursuit of Logic Part III: When Factual Arguments Fail – Almost Always

In Pursuit of Logic Part IV: Animals and Plants Have the Right to be Left AloneTHE CONCLUSION – In Pursuit of Logic Part V: Science Provides, Wisdom will Lead

One Comment on “Alien Shrubs From Mars?

  1. Thanks, Rick! I liked your closing statement about the rights of Nature—to be left alone. This is important when it comes to water use, too. Nature has a right to keep it’s water on-site. Water is often drained from creeks and groundwater supplies without concern for the wildlife it supports.

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