After the massive 2017 firestorm that hit northern and southern California, it is important to take a look nature’s relationship to fire and how nature has been characterized in the wake of what has happened. For this discussion, we will be focusing on the fires in Napa and Sonoma Counties, although most of what we write is directly applicable to the Thomas Fire in Ventura and Santa Barbara Counties as well.
How We Talk About Nature. First and foremost, we need to reframe the discussion and consider the words we use. Nature provides beautiful habitats for a wild diversity of creatures. It is not “fuel.” Fuel is what we put into our cars and what heats and cools our homes. A dense thicket of shrubs offers the wild foundation of green for countless organisms from lichens to wrentits. It is not “overgrown.” The term “overgrown” can be used to describe our gardens and backyards perhaps, but it’s not an appropriate or accurate way to describe our wildlands, no matter how many fire or flood cycles have been missed. Saying nature is “overgrown” is at best, derogatory. “Overgrown” is a highly subjective term based on hubris, not the needs of a woodrat, a Scrub Jay, or a ceanothus silk moth.
Words matter. Due to the loaded terms that are continually used to describe the natural environment, it is no wonder that a significant number of politicians and members of the public either fear or distain nature and see no reason why we should protect it. To them, terms like fuel, overgrown, brush, and dead trees, have become bludgeons to attack those of us who want to protect the rapidly vanishing natural environment and as an excuse to log, clear, and eliminate our public lands.
Natural Fire Return Intervals. The best way to determine what the natural fire cycle is for an area is to examine the frequency of lightning-caused fires.
Napa and Sonoma Counties have some of the lowest lightning frequencies, and hence lightning-caused fire, in California. From 1919 to 2016, Sonoma County had a total of 489 fires per million hectares per year. Only 6 were from lightning (the rest have been human- or unknown-caused). In contrast, the half-million hectare northern California County of Siskiyou had 44 lightning-caused fires in the year of 2004 alone. Therefore, before humans arrived in the Napa/Sonoma region, fires of any significance were likely spaced over relatively long periods of time, probably on the order of 50 – 100 years or more. This kind of fire return interval cannot produce the fire suppressed/”overgrown” environment the media has described. We have a response to one of the worst examples of reporting like this on our chaparral blog.
When discussing natural fire return intervals, people often ask about Native American burning.
We know they burned the landscape. Exactly where and how frequently is a subject of much debate and is mostly knowledge lost in time. But it is fair to say that early Native American burning was likely responsible for creating some of the patchiness of plant communities in the Napa/Sonoma region as well as in other areas. It is also reasonable to hypothesize that Native American burning, especially around villages, began the process of eliminating native shrublands in favor of more open landscapes.
As with wine makers who clear their land for vineyards, Native Americans modified the land to obtain what they wanted as well.
Interestingly, the loss of chaparral in California due to type conversion has been discussed in one of the earliest works on chaparral by William Cooper (1922). He did some, as he wrote, “painstaking” searches to locate remnants or relic stands of chaparral in areas presently dominated by non-native grasslands in northern California. He also interviewed a number of old timers who remembered what the place looked like before the onslaught of settlers changed the place forever. He found ancient chamise shrubs along fence rows, on rocky ground, in ravines, etc., where humans and cattle couldn’t finish off what was left (Fig. 1 below). He discusses several relic sites in Colusa County near Arbuckle, in the Santa Clara Valley, and near Hershey in the Sacramento Valley. He also suggests that the impacts by European ranchers/settlers were, “of small importance compared with the effects produced by the aboriginal population” due to yearly burning practices.
The steady transformation of California’s wilderness began about 10,000 years ago after the arrival of America’s first peoples.
The frequently heard call that we should return to what we think Native Americans did on the landscape is counterproductive to our current efforts to protect what natural environments we have left. With millions of people lighting fires, the climate changing, and invasive, non-native weeds that Native Americans never had to deal with, when it comes to land management, it is best to consider the challenges we are facing in the future.
Fire and Habitats Today. So how does this all figure into our land management today? We obviously cannot allow what few natural fires we have to run their course in populated areas. And we certainly can’t let human-caused fires run. Hence, we suppress. In wildland areas far from communities, we can let fire play it’s natural role. Most natural parks do this now. Sometimes, however, the public and their elected leaders do not have much patience for that.
For example, a fair number of career land managers lost their jobs after the lightning-caused 1988 Yellowstone fires due to a general ignorance about how wildfire operates in that region. The forest that burned was composed of lodgepole pines. The natural fire return interval for such forests is between 135-185 years at low elevations and 280-310 years at high elevations. When such forests burn, they burn at high-intensity and they burn big. Ironically, many blamed the widlfires on “fuel” buildup from past fire suppression (and still do). The fire return interval for Yellowstone forests predates the fire suppression era.
Given the low, natural fire return interval in Sonoma/Napa Counties (using lightning as a proxy since there is little else to go on), it is likely that huge, landscape altering wildfires like the 1964 Hanly Fire and the recent Tubbs, Nuns, and Atlas Fires, visited the region once or twice a century when all the cards lined up – several years of drought, low humidity, and winds. Before such fires in northern California, trees likely moved into chaparral, chaparral moved into grassland, and grizzly bears owned the place.
However, since we have lost so many wild habitats, it is reasonable to artificially manage what is left. If one vegetation type invades another, and we desire to maintain a balance of the habitats we want, it is logical to use artificial fire and thinning projects in forested areas to do so. But we need to continually remember not to confuse our efforts with the natural pattern. We are artificially managing wildlands because we value a certain mix of habitats.
There have been some attempts to quantify natural fire return intervals with mixed results. Hugh Safford and Kip Van Water (2014) have done perhaps the best work to deal with this on a statewide level. I have provided a link to their paper at the end of this email. Safford and Van Water have shown there are basically two California’s – southern California which is suffering from too much fire, and the higher elevation forested regions of northern California having a fire deficit.
One of the least helpful effort to figure out fire return intervals has been the LANDFIRE project, coordinated in large part by the Nature Conservancy. This is mainly because, at least when it came to chaparral and other non-forested communities, they guessed… a lot. For example, the folks putting the California portion together called me and other fire scientists familiar with chaparral and asked what the fire return interval was for particular areas. We all indicated that the data was pretty clear for the southern part of the state, but for the other areas like the Sierra Nevada, we just don’t have the information to make a proper estimate. They asked us to guess. We informed the person who we were talking to that we wouldn’t do that. They called back later and asked me to just come up with a number they could use. We said no and asked them not to call me again. We have no idea who finally guessed a fire return interval number for these places, but it was no one who had a handle on the actual research. And it certainly wasn’t supported by data.
For chaparral across the state, the natural fire return interval has been fairly estimated to be between 30 to 150 years or more. The lower end is based on the system’s ability to create a sufficient seed bank and starch stores in root burls. The upper end is based on the oldest manzanitas we have found. The notion that many in the past claimed that chaparral needed to burn every 10 to 20 years is difficult to fathom. It certainly wasn’t based on science. Here’s a paper we wrote awhile back that takes a look at how attitudes and ideas have changed about chaparral over the years.
Chaparral Type Conversion in Northern California. There is no question the chaparral in northern vs. southern California is different. However, it’s sensitivities to fire are the same. Cal Fire justifies truncating northern and southern chaparral in their proposed Vegetation Treatment Program because they say there haven’t been as many fires in the north. This is true, for now.
Unfortunately, southern California (i.e. fire, heat, people) is heading north due to climate change and population growth (and eventually migration, induced by climate change).
Several years ago, we gave a presentation in Santa Barbara and discussed the type conversion of chaparral. During a panel discussion, a fire manager said they do not have that problem in Santa Barbara because the fire patterns are different than they are in the south. A few months ago the same fire manager let me know that, unfortunately, he was starting to see chaparral type convert in the 2016 Rey Fire area over the mountains behind Santa Barbara. Many are now very worried about it, in terms of habitat loss and flammability issues (grass is more flammable than chaparral).
This is why we must look to the future when managing our landscapes, not base our decisions on what has happened in the past.
The work of Park Williams, Tom Swetnam, and Craig Allen will help drive that point home. Their work is based on a robust data set from tree rings in the Southwest. The data points have been used to create an index # (FDSI) that generally reflects tree ring width – thinner the ring, the worst the drought that year. It is applicable to California via comparable research on oak trees.
Fig. 3 below shows all the drought periods over the past 1,000 years (gray is the actual data point, red is the smoothed out average). The orange circles mark the three devastating droughts that eventually destroyed the Anasazi culture (the people who built the cliff dwellings). The green circle was where we were in 2015.
Fig. 4 below shows the predicted drought cycle over the next 100 years. We appear to be within a short rebound with higher moisture (blue arrow). It is predicted, however, that things will get drier again, and soon (red arrows). By 2050, the typical drought (green line) will be worse than the extreme drought level experienced over the previous 1,000 years (bold dotted line).
We must manage our landscapes with these projections in mind. Ironically, the very habitat that is often demonized and cleared on a continual basis, chaparral, may very well be one of the few native plant communities that will remain viable, albeit at higher elevations and further north. This is why the Cal Fire viewpoint on chaparral in northern California is so twisted. If we care about future native habitats, we really cannot afford to compromise native shrublands anymore, much less demonize them. We need to rejoice in their value to us (ecosystem services) and the creatures that call them home. We discuss some of this in our paper on chaparral diversity.
Dead Oak Trees. We have been working with Matteo Garbelotto at UC Berkeley to understand the role dead/diseased oak trees played in the recent fires. Unfortunately, several articles misrepresented what Matt has said, claiming in bold headlines that sudden oak death played an important role in how the fires behaved across the landscape. That was not journalism, it was hype of the kind we often see in wildfire reporting.
Matteo contacted the paper and tried to get the article corrected, but to no avail.
Here is what Matteo wrote for an informational booklet being written now about the Napa/Sonoma fires:
“The relationship between fire behavior and tree pests or diseases is far from straightforward.
While the evidence points to a positive relationship between disease and fire, most evidence also indicates the relationship is strongly time-limited. This means that while disease and pest outbreaks may increase fire intensity (how much energy the fire releases), they normally do so only for a limited window of time. In general, disease and pest outbreaks in their middle stages have the greatest effects, while very recent or distant outbreaks have very a limited effect on fire.”
In the actual areas that burned, dead/dying oaks are far and few between. Fig. 5 below shows dead/dying oaks (red) from the Sudden Oak Death database. Fig. 6 shows Cal Fire’s map of where dead trees are across the landscape. I’ve also included a map of the fire perimeters for reference (Fig 7). It is not likely these few trees contributed much in the way of fuel for the fires except on a very localized basis. None of the large clusters of dead trees on the Cal Fire map were even located in the areas burned.
The Fire Suppression Story. Terrestrial Nature in California (forests, shrublands, and grasslands) represents one of the earth’s treasures. It is dense with life.
The word “overgrown” only enters the conversation when humans assert their value system.
Are some forests denser than they have been in the past in some areas due to fire suppression efforts? In some cases, yes. But what wildfire agencies, fire managers, and the public typically fail to understand is that the densest forests that cause most of the hand wringing are the way they are not because of fire suppression, but because of how corporations butchered our forests before Teddy Roosevelt, John Muir, and others said no more.
Massive clear cuts, followed up by intense over grazing, created huge, open scars across the landscape – Humboldt, Placerville, the redwoods in and around Santa Rosa, and elsewhere. The second or third growth we see today is a pathetic little stick forest compared to what once was (Fig 8). In areas where the lumber companies and the US Forest Service didn’t plant overly dense tree farms, the forest floor exploded with new seedlings because there was so much light. Then came fire suppression to protect the lumber (and people). Perhaps expectedly, government firefighters have gotten the blame for it all. Corporate greed is never mentioned.
So yes, prescribed burning and some thinning in these kinds of damaged forests is justified. The problem comes in when people exploit the fire suppression story to log and clear habitat for their own personal gain.
But those are forests – mid elevation forests below 7,000 feet, the western Sierra Nevada, and some forest habitat islands in southern California. This fire suppression story is not applicable, however, for the rest of the state.
The Fire Suppression Myth. For most of California, especially where lightning frequency is low, past fire suppression efforts have not increased the density of life. Wildfire agencies and managers need to stop implying or actually making the claim that it has. Unfortunately, a lot of that was being said after the Napa/Sonoma fires.
Headlines and articles in High Country News and Bay Nature shouted out how “shrub-choked wildlands” and “overgrown” grasslands were responsible for powering the flames. Yes, “overgrown” grasslands. The whole state is “overgrown,” the myth goes, and in immediate need of prescribed burns and clearance.
Such commentary is not harmless. It demonizes nature, mischaracterizes fire, and promotes environmentally harmful land use policies.
In terms of the human environment, the fire suppression myth makes us think we can clear, log, and/or prescribe burn our way out of the fire hazard mess we have created by our profit-driven exploitation of the land. And the myth appears to provide an easy answer to our problems – do enough clearing in different ways and we can create fire resilient communities (both natural and human-made) where all will be safe. It aligns with what a lot of people have always been doing, and provides the rationale for funding fuel modification programs like Cal Fire’s. It deludes us into thinking we have control over nature. And it ultimately facilitates the continued building in very high fire hazard zones, destroying increasingly large amounts of native habitat while doing so.
There are multiple research papers showing that vegetation build-up from fire suppression has not occurred in most of the state and that the age of vegetation in native shrublands is not responsible for the occurrence of large fires. Nonetheless, the myth persists.
A Final Word About “Fuel.” Fires cannot burn without fuel, so every fire has some fuel-based component that drives it. However, the problem with the fuel-centric approach to reducing fire hazards for humans is that when the dangerous fires occur, it doesn’t matter if it’s trees, shrubs, grass, or houses – the fire will burn until the weather changes or the ember rain exhausts itself over concrete or a body of water. When it comes to what’s burning, most of the surrounding plant life is ignited by the homes, not the other way around. This is what happened in Fountaingrove and Coffey Park. It’s also what happened in the Oakland Hills 1991 Tunnel Fire, which started in grassy fuels as most California wildfires do. The million acre plus 2006 fire in Texas that killed a dozen people and burned hundreds of structures was driven by burning grass, grass not unlike what has replaced many native habitats in Napa and Sonoma Counties and invades many vegetation treatments.
When driving around the areas burned in the Tubbs, Nuns, and Atlas Fires, we were struck by the amount of low to moderate severity burning we saw. Oak woodlands and mixed conifer forested areas had some high-severity patches (which are critical for a whole array of wildlife), but for the most part, their canopies remained intact. Chaparral patches burned with high severity as is its natural pattern. Ecologically, the fire generally did what was expected for the plant communities involved.
The problem comes when this reality collides with human communities and people want to blame nature. Contrary to what was claimed, the areas burned in the 2017 wildfires were not “overgrown” wildlands “choked” with shrubs. They were landscapes in which people were put in harm’s way. The sooner we address the problem in those terms, the sooner we start protecting families and communities from wildfire.
Here’s two excellent references on fire that are particularly relevant to northern California:
Safford, H.D. and K.M. Van de Water. 2014. Using Fire Return Interval Departure (FRID) Analysis to Map Spatial and Temporal Changes in Fire Frequency on National Forest Lands in California. USDA. PSW-RP-266.
And here’s an intriguing article on how aboriginal burning has transformed large landscapes in the southern hemisphere:
The 1922 study of chaparral by Cooper can be found at used book stores on the net: Cooper, W.S. 1922. The Broad-Sclerophyll Vegetation of California. An Ecological Study of the Chaparral and its Related Communities. Carnegie Institution of Washington. Washington, D.C.
The excellent book by Carsten Lien (2000) about the century long battle to protect the old-growth forests of the Olympic National Forest is a much read for anyone who wants to learn what it is like to fight for nature and forces one must contend with. Lien, C. 2000. Olympic Battleground. The Power Politics of Timber Preservation. The Mountaineers Books, Seattle, WA.