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Treebeard's Stumper Answer
17 September 1999

Wild Fire

Fire is on my mind. It's our first topic in science class. It's also the peak of the wildfire season, and I live in the woods. We witnessed an arson-caused fire on our way to the Sierras and watched bombers drop retardant. The week before, lightning started a fire near Red Rock, too close to home. There have always been lightning strikes and summer-dry chaparral ready to burn. But bombers and hotshot crews are something new. What controlled wildland fires before modern procedures? Did the whole state burn at once?

Fire on the hills
Lightning-caused fire burning into the backcountry behind Red Rock on August 26, 1999. Santa Barbara city firefighter Stephan Masto died fighting this fire, apparently from heat stroke.

I suppose an uncontrolled fire could spread until winter rains put it out, but I don't think that was typical in old California. Fire is mainly controlled by other fires. Burned hills become natural firebreaks. Fires burn upwards and become isolated. The fire mosaic of past burns limits the spread of future fires. We've learned the hard way that suppressing fires can make a bad situation worse, increasing fuel loading so the inevitable conflagration becomes unstoppable. Managing wildfire in our mountains is a huge problem with no easy answer.


This hand-made map of wildfires in the mountains behind Santa Barbara shows how complicated a real fire mosaic can be in the California chaparral:

Santa Barbara Fire Map
Historical fires in the mountains behind Santa Barbara, California. This map does not include post-1980 fires, including the 1990 Painted Cave Fire that burned south across Highway 101 and threatened Santa Barbara itself.

Graybear sent this answer, and a new stumper that I should have thought of:

The thing to realize and remember is that, since these fires were frequent, there wasn't as much fuel available and each individual fire was small compared to the potential of modern forest fires. That is why some foresters perform controlled burns of wilderness areas - the small fires remove the undergrowth without killing the trees, rejuvenating the forest and encouraging new growth.

Can you name any natural causes of fire other than lightning? (I'm thinking of three others.)

Good question! I put this to the kids in my science classes at Dunn Middle School. Here's our answer.

You can learn a lot about wildfire by burning sheets of paper. Light the edge of a sheet of newspaper on bare ground and watch the fire line move across. Be careful you don't start a real wildfire! Some parts burn faster than others along a complicated boundry, and some areas get left behind. It might well go out before it all burns. This demonstrates how natural fires can burn themselves out to create a piece of a fire mosaic. This won't surprise anyone who's ever tried to start a campfire with just one match!

You can simulate fire behavior with a simple cellular automaton model. Start with a checker board of empty [unburned] squares. Start a fire on a center square by placing a red [burning] checker. Now flip a coin (p = 0.5) for each of the four empty neighboring squares. If it's heads, then the fire spreads, and that square gets a red checker. Otherwise leave it alone. After testing all four directions, replace the original red checker with a black [burned] checker. Repeat this for each red checker still on the board until there are none left. Of course, burned squares can't burn again and can be ignored. Most "fires" will go out by themselves leaving a piece of the future fire mosaic with interesting fractal boundries. You can simulate the effects of wind and topography by changing the probabilities in different directions. I wrote a DOS BASIC program to do this simulation, available in the links below. Here's a typical screen shot from my program:

Fire simulation screen shot
This is a screen shot from my LIFE-ETC fire simulation program. This "fire" began from a single red burning square in the center. Many parts have gone out on their own forming a fractal boundry, though there are still red hot spots on the edges.

"I have this sense of impending doom..."
- Stephan Pyne, author of Fire In America

Julie and I live on the north-facing slope of the Santa Ynez Mountains that form the east-west mountain wall behind the city of Santa Barbara. This is a cool woodland of Coast Live Oak, Madrone, California Bay, Tanbark Oak, and other plants more typical of woods to the north. From my porch I look north across the head of Los Laurales Canyon at the steep south-facing slope of Fremont Ridge. That slope looks and feels very different. It's hot because it faces the sun all day long. It's a dense chaparral community with separate areas of Eastwood Manzanita (arcotstaphylos glandulosa) and Chamise (adenostoma fascicularis), plants that not only burn well, but actually require fire to propagate and are adapted to quick recovery. From my porch, the chaparral looks uniform, almost like a smooth lawn. It's all about the same height and age. Last summer I managed to bushwack through this chaparral to a rock outcrop I can see from my porch. Mostly I crawled on my belly and regretted it.

My house on north-facing slope Fremont Ridge on south-facing slope
Looking south at my house in woods on north-facing slope.
Looking north from my porch at chaparral on sorth-facing slope.

That uniform chaparral is surely the result of a single fire, probably in 1940, but maybe during the great 1955 Refugio Fire that burned 25 miles in just 30 hours. It's ready to burn again, and this is the height of our fire season, made worse by occasional tropical lightning storms and santa ana or sundowner winds. Last winter's freak snow storm brought down many of our trees and makes it worse. This is a forest of gasoline ready to ignite. These mountains will burn.

My hope is that a hot chaparral firestorm will pull the fire away from our wooded side of the canyon. But I'm not optimistic. We have large and small oak trees. But there are areas in the woods where there are dead and dying chaparral shrubs now shaded out by trees. Our Bay and Madrone trees usually grow from huge underground burls that re-sprout after fires. I can read some of our fire history in this evidence.

Fire suppression efforts have made the situation worse in the long run. Robert Minnich has published interesting work using Landsat satelite images to compare California with northwest Baja California, where fire control is not so effectively practiced. He writes:

The present regime of large, intense conflagrations in southern California chaparral appears to be an artifact of fire suppression. The great acheivement of suppression is the extinguishing of small fires. Once fires are large, man has trivial impact on their progress.

In effect, a fine [fire] mosaic has been replaced by a coarser one. There is no evidence of such large fires in the Baja California chaparral mosaic.

The creation of chaparral mosaics in southern California is highly desirable since the mosaic is the basis of fire control. Fires would become smaller and would be distributed more evenly over time and space. Such was apparently the case in southern California before fire management.

Part of the answer is controlled burns and fire breaks. Like we say, fight fire with fire. But the record is not so good here in Santa Barbara. Controlled burns often cross fire lines and go out of control. There are always city complaints about the smoke. I've noticed that controlled burns (and especially hand-cut fire breaks) are often overgrown by invasive weeds like Yellow Star Thistle (centaurea solstitialis) instead of our native fire-follower plants. This suggests that these fires don't burn hot enough to do their job. When I see smoke, I worry that the weather's too hot for a controlled burn; but then it doesn't burn hot enough to do the job. I'm not objecting. It's just not enough.

Yellow Star Thistle on fire break Yellow Star Thistle on fire break
Exotic Yellow Star Thistle (centaurea solstitialis) taking over fire break on ridge north of Painted Cave.

In the long term, I think there's only one answer. Get all people (yeah, me too) out of these mountains and "burn, baby, burn." But it won't be easy.

I found lots of information about wildfire on the Web, but no single site addresses the controversies. Try a web search on "fire mosaic" or "controlled burn". Here are a few starting links to explore:

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