CHAPTER 6

LIVING WITH THE CHAPARRAL

THE BEAUTY AND UTILITY of chaparral is tempered by inherent problems and dangers. The gentle plain of Santa Barbara to the Sierra foothills and the bucolic canyons of the Santa Monica Mountains all bear testimony to the power of chaparral wildfires to invade our cities and suburbs (pl. 74). In the aftermath of a chaparral wildfire on steep terrain, the bare steep slopes become unstable. Heavy winter rains can quickly create a massive slug of water, mud, and debris peppered with boulders that surges uncontrollably down slopes and canyons into settled areas. These viscous flash floods can materialize suddenly and with no obvious warning, so that people in their path have almost no time to prepare or to flee.

Chaparral wildfires that destroy property, and sometimes take human lives, are not acts of God that abruptly and capriciously materialize, striking down the unsuspecting. They are quite comprehensible and predictable, in the same sense that floods are predictable for people living on the flood plains of rivers in other parts of the United States. Dwelling on the 20-year flood plain does not mean that a house will experience a flood at 20-year intervals, or ever, within the tenure of a particular occupant, but rather that the chances of a flood in a given year are one in 20. Similarly, living in chaparral where fire has come three times in the past century does not mean the next fire will come precisely 33 years after the last. After the shrubs reach the point where they contain enough fuel to readily burn in dry weather, each passing year without fire slightly increases the potential flammability and probability of fire the following year. So the risk of flood or fire is more like that found in the actuarial tables of life insurance companies, where the older one becomes the greater becomes the probability of death. People sometimes conclude that a particular location in chaparral is safe from fire or flood because it has been many years, perhaps longer than a human lifespan, since disaster has struck that particular place. The same wishful thinking permits some people in an area with high seismic risk to live or work in a building that has stood for many years even though it would be quite dangerous in a strong earthquake. Upon a landscape shaped by episodic fire or flooding it is wishful thinking to assume that these recurring events will cease. It is just a matter of time until disaster strikes.

Plate 74. A house located at the top of a canyon burns during the Malibu fire of 1985.

Even though chaparral wildfires are inevitable, and under some circumstances may even be desirable, the first concern of residents and public officials alike is protecting lives and property. For about 100 years this concern has been addressed with policies of fire prevention and of extinguishing fires as quickly as possible when they do occur. Necessary and expedient as these policies may be, they are not a complete and satisfactory way to deal with wildfires in chaparral. Moreover, other management goals, such as fuel reduction, watershed improvement, and wildlife habitat enhancement, require different responses. Fire is inevitable wherever chaparral occurs. Any policy that fails to recognize this fact is fundamentally flawed.

Prescribed Fire

One tactic for reducing the danger of living near chaparral is to use fire to reduce the volume of fuel in critical areas. This is sometimes done by deliberately burning patches of chaparral in a carefully controlled fashion. The idea of intentional burning—prescribed fire—is to buffer urban areas adjacent to cities with chaparral that is young enough to retard or stop a wildfire approaching from distant, older, and more flammable chaparral. Prescribed fire has gradually assumed an important role in the control of chaparral wildfires as managers have realized how useful it can be in the long term, resulting in fewer large wildfires, less loss of life and property, and lower expense. Prescribed fire may be used to burn patches of hundreds to thousands of acres, or it may be employed to create smaller natural clearings in the potential paths of destructive wildfires. The photograph at the beginning of chapter 3 shows a large prescribed fire done for research purposes during summer burning conditions. Since fire after fire often follow a similar path through mountain passes and along hillsides, it is possible to predict the most likely places for large fires to occur. For example, patterns of Santa Ana winds and urbanization mingled with large and continuous stands of chaparral have pushed destructive wildfires along the same avenues of chaparral time after time. One way to break these patterns is by removing wide swaths of mature chaparral right across the potential fire paths. Prescribed fires can sometimes provide this kind of clearing so that fires can be more easily and safely blocked before they move into areas where lives and property are at stake.

The shift from the failed policy of suppressing all chaparral wildfires to using prescribed fire as a management tool has not been simple or easy, and it still is not. A number of difficulties and limitations will always make the widespread use of prescribed fire in chaparral and elsewhere problematic. The possibility of an escaped prescribed fire will always be something that causes managers to think long and hard before authorizing ignition. Fire managers know how to predict the general behavior of burning chaparral by using careful measurements of weather conditions, characteristics of living and dead fuel in the chaparral itself, and topography. All of these variables can be entered into computer models that help to predict how fire ignited at a particular time and place will burn and spread. The accuracy of these fire predictions is only as good as the weather forecasts upon which they are based, especially the information on wind and relative humidity. The areas to be burned are carefully prepared in advance, so that various kinds of natural and artificial barriers will prevent a prescribed fire from spreading outside of the intended perimeter. The prescription for a particular fire specifies maximum and minimum acceptable levels of temperature, relative humidity, wind direction and speed, and fuel moisture. If there are any deviations from these prescribed conditions, the fire will not be attempted. The goal is to ignite chaparral when it is dry enough to burn, and for flames to gently move through the intended fuel. It must be possible to contain the fire under these conditions. I (R.Q.) once observed the ignition of a management fire when prescribed weather conditions were met, but shortly after ignition the wind direction shifted, which doubled the level of relative humidity in a matter of minutes. The chaparral quickly became too damp and the fire went out without spreading at all.

The greatest risk in prescribed burning is a sudden and unexpected change in the weather after the fire has been ignited, such that it causes the fire to become unmanageable. Under the right conditions, a prescribed fire may escape despite the most careful plans. On one unlucky day in spring, Santa Ana winds that had not been predicted suddenly developed in southern California, which caused several prescribed chaparral fires that were burning in various places at the time to get away. The risk of escape rightly causes decision makers to err on the side of caution. An escaped prescribed fire will be remembered far longer than the many successful and safe burns, particularly if it causes damage. Months and even years of careful planning can come to naught in the face of a dry spring or persistent winds. Often there is nothing to do but wait another year and hope for more favorable weather. These difficulties notwithstanding, prescribed fire holds out a useful and relatively natural method for reducing the chaparral fire hazard in selected areas. It can be a useful tool for small stands of chaparral near urban areas, but it will never be practical in most chaparral because prescribed fires are expensive to plan and execute, particularly in rugged areas with limited access.

Public perceptions and opinions about prescribed fire are another important ingredient in its usefulness. Most people are not accustomed to seeing chaparral or any natural vegetation deliberately burned. Without some explanation they may be disapproving or even alarmed at the prospect. It is especially important that nearby residents, who may treasure the scenic value of mature chaparral, understand the purpose and necessity of burning parts of it in the interest of public safety. There have been instances where federal, state, and local agencies have found their efforts to reduce chaparral fuels with prescribed fire thwarted by people who did not want vegetation deliberately burned on or near their properties and communities. Smoke is a related community and regulatory concern. Much of California's chaparral lies on hillsides adjacent to valleys with polluted air, so that fire managers are permitted to burn only on days when smoke from the fire will not add to local smog or cause discomfort to people living nearby. The requirements of laws protecting endangered species of plants and animals can further complicate planning of prescribed fires, because no action can be undertaken that might harm such species.

Prescribed fires are generally ignited in late spring, after fuel moisture has dropped sufficiently for chaparral shrubs to burn but before the vegetation dries out sufficiently to produce such an intense fire that might be difficult to control. Fire at this time may cause more damage to soil, seeds, and reproducing animals than fires in other seasons. Studies have shown that spring fires cause different and more severe changes in many biological processes in the soil, especially if soil moisture is present, than do fires over dry summer soils. Spring burning can disrupt or terminate reproduction of birds at the peak of the breeding season. Populations of chaparral plants can lose an entire year's reproductive effort if flowers or fruits are present on the plant when it is burned, as often is the case in spring. These multiple impacts on ecological processes caused by spring burning can retard the recovery of chaparral vegetation and may ultimately shift the species composition. Prescribed burning of chaparral can be done in winter, the other season when wildfire is unlikely. However, low temperatures and high fuel moisture often make it difficult to impossible to burn stands of living chaparral shrubs at this time. Winter burning can be used to safely remove piles of dead vegetation during weather when surrounding shrubs are virtually incombustible.

Sometimes firefighters will deliberately set a prescribed fire, called a backfire, in the path of a spreading chaparral wildfire. Their goal is to deprive the uncontrolled fire of fuel when it reaches the place where the backfire has already consumed the vegetation. This is done in places where a barrier, such as a road or clearing, can prevent the backfire from spreading in the same direction as the wildfire, which is usually the way the wind is blowing. This is done only when few other options exist for stopping a wildfire, because there is always the danger that the backfire will spread and become part of the fire it is intended to block.

Fuel Reduction and Fuel Breaks

The fuel contained in chaparral shrubs can be reduced on a local scale by a number of methods. Bulldozers, often pushing or pulling large implements, can roll, chop, crush, plow, or otherwise reduce shrubs to small pieces that lie upon or within the soil. In this state they are incapable of carrying an intense fire. Most of these mechanical methods cause severe soil disturbance and may kill the root systems of the shrubs and other perennial vegetation. In very small areas, hand labor similar to that used to build fire lines can be employed to thin or cut shrubs. This method is expensive because it is labor intensive. Shrubs or their stumps may be killed through treatment with herbicides. This method must be used with great care because of the potential damage from chemicals to the environment and other organisms. If intact dead shrubs are left by any of these methods, they must be removed by bonfires or in some other way before the next fire season, because they are far more flammable dead than alive.

Goats are an increasingly popular tool for reducing the volume of chaparral shrubs in small areas. These animals will eat almost any kind of chaparral vegetation, and the amount and type of plant material they remove can be governed by herding. Goats can be cost-effective because as they reduce fuels they are being fed free of charge, all the while producing valuable products such as Angora wool. Goats, unlike cattle, must be closely tended because they are sensitive to cold or wet weather and are subject to predation by Coyotes (Canis latrans) and Mountain Lions (Puma concolor).

Under extreme conditions chaparral wildfires can spread furiously in any direction the wind blows, fed by voracious consumption of the shrubs. One way to thwart the spread of a wildfire is to deprive it of additional fuel. In some places this is done by creating long roadlike gaps in otherwise continuous chaparral by removing most or all of the shrubs. These barriers to fire, called fuel breaks, are often constructed in broad swaths between urban areas and expanses of chaparral in adjacent wildlands (pl. 75) using a selection of the methods described above. A progressing wildfire can sometimes, but not always, be safely stopped at a fuel break. As described later in this chapter, under extremely dry and windy conditions chaparral wildfires can spread furiously, and flying embers and firebrands can easily carry fires across fuel breaks and even much wider barriers. Fuel breaks 200 to 300 feet wide are best employed as part of an integrated fire management plan that includes other means of fuel reduction as well. As shown in pl. 75, fuel breaks are often placed along ridge tops because these are places where fires that have raced up slopes under the propulsive force of convection tend to naturally slow down. Ridge tops are also places in rough terrain where firefighting roads can be most easily constructed.

The edges of fuel breaks are often deliberately made irregular, because this produces a more pleasing and natural appearance. The look of a fuel break can be further softened, without losing its effectiveness, by leaving small patches of chaparral in especially wide places. Even trees can safely remain in some places as long as all lower and dead limbs are removed so that a ground fire cannot climb into the tree canopy. After shrubs have been removed, fuel breaks are usually planted with another type of vegetation that does not pose the same degree of fire hazard as chaparral, such as perennial grass or other plants that grow close to the ground. This cover vegetation reduces the danger of erosion and also improves the appearance and wildlife value of fuel breaks. The clearings of fuel breaks can become inadvertent avenues for invasion by plants that grow well in places where the soil and natural vegetation have been disturbed and reduced. These plants are usually nonnative species, and they can spread into uncleared chaparral areas, especially after fire.

Plate 75. Swaths of cleared land adjacent to an urban area form fuel breaks in chaparral, in the San Rafael Hills, Glendale, California.

Fuel breaks are expensive to construct and require regular maintenance in order to retain their effectiveness. Their cost is such that they are unlikely to be placed throughout chaparral or around every settlement or dwelling near chaparral, but their strategic use can be of enormous benefit to firefighters. Chaparral wildfires have been slowed and stopped by fuel breaks, and attendant damage greatly reduced, in all parts of California. In some cases this has broken a historical pattern of wildfire spread, reducing potentially large fires to much smaller dimensions. In principle, the money fuel breaks save by reducing the cost and damage of a threatening wildfire can be greater than the cost of the fuel break itself, in addition to the benefits of reduced danger and human suffering.

Artificial Seeding of Burns

Seed of annual grasses, especially Italian ryegrass (Lolium multiflorum), has often been scattered from aircraft on burned chaparral slopes. This practice is an attempt to establish plant cover quickly on a denuded landscape, with the expectation that there will be less soil erosion from land covered with plants than from bare soil. While ryegrass seeding on chaparral burns has gone on since the 1940s it is of questionable value. Most chaparral ecologists and environmentalists oppose the practice, having concluded from research that over the long run the practice may actually make erosion worse. In addition, it may disrupt the native plant community.

It might seem obvious that the faster a burned slope is covered with well-rooted plants, the less erosion when rain falls. However, the vigorous growth of ryegrass requires gentle and evenly spaced rains throughout winter—conditions seldom met, particularly in southern California and the Sierra Nevada. It is more likely that the majority of rain will fall, with attendant erosion, before ryegrass seedlings become well established. If rainfall is spread out through winter so that ryegrass grows well, then the spreading grass can compete with the growth of seedlings of chaparral shrubs. Moreover, when the annual ryegrass dies the following summer it can provide a fine, continuous fuel that could easily carry a second fire across the same landscape. A reburn at this time would kill all chaparral shrub seedlings and injure or kill resprouting shrubs as well. An additional problem with ryegrass planting is that the vigorously growing grass plants may out-compete the native fire annuals and other herbaceous plants. This produces a cascading negative effect, because if the native plants do not survive to flower and set seed, then there will be fewer seeds in the soil to repopulate the area with natural chaparral plants after the next fire. Once set in motion, this process, reinforced by subsequent fires, could eventually lead to the complete elimination of native plant species including the ground-holding shrubs that control erosion naturally.

Seeding with nonnative plants after chaparral wildfires continues to be practiced for two reasons, despite all the evidence that it is an ineffective practice for both erosion control and for conservation of the native flora. First, it is something managers know how to do and traditionally it has had public support. It is “something” that can be done. Second, even with all its potential problems, it is not possible to predict exactly what will happen in any given instance after ryegrass is sprinkled from the sky onto a blackened chaparral hillside. Seeding aside, it is not possible to predict exactly what species of plants will come up in a given location, or when or in what numbers, and harder still to conduct any practical research that would provide a universal set of management recommendations. Many ecologists and environmentalists have suggested that no further artificial seeding of any kind be done in burned chaparral. A compromise would be to use the seeds of native chaparral plants in place of the exotic grasses. In recent years some public management agencies have been directed to do so when practical. This is occasionally done, but not often. Very large quantities of seeds from native annuals are difficult to obtain on short notice, and they are expensive. Furthermore we have no information on how well native plants might germinate and grow when introduced in this way, much less whether they might retard erosion any more effectively than naturally occurring seedlings. Equally important, there is no assurance that large numbers of introduced seedlings of native plants would not destabilize populations of seedlings of other species of plants natural to the site. It is clear that artificial seeding of any kind has the potential to produce results that are different from what occurs in naturally recovering chaparral. The long-term consequences of these changes are unknown and unpredictable.

Fire Causes Its Own Weather

The peak fire season in California chaparral is correlated with the end of the rainless summer, which can bring hot, dry weather and erratic winds. However, these are not the only weather conditions that cause the spread of fire. Once a wildfire builds to sufficient intensity and size, it can create its own weather, a firestorm, causing it to build upon itself and gather the potential to start new fires. This occurs because air heated rapidly at ground level by the fire creates strong updrafts as it rises. The internal turbulence from the smoky, hot air traveling upward in enormous columns can rapidly draw in more air along the ground, and this wind erratically pushes the fire in new directions. In addition, this upward movement of hot air pulls along embers, firebrands, ash, and smoke as it rises. Once a hillside is on fire, the masses of surging, fiery debris and smoke can be propelled upward to as high as 20,000 feet! There the clouds begin to cool. Meanwhile these churning masses of hot air and debris are moving in the air currents hundreds to thousands of feet above the fire. These drifting fire clouds sometimes rain burning pieces of wood, ashes, and cinders as far as several miles from the original source. The fire's own internal weather system also creates gusty windstorms over a wide area. Consequently, the original fire is driven and spread erratically in the face of the unpredictable forces of the firestorm. It is almost impossible to contain a wildfire in chaparral when it is driven by strong winds. The winds spread the fire clouds and fan the smoldering bits inside them so that once dropped to the ground, they are likely to start satellite fires. As these secondary fires build up, the entire process can be repeated. When it is very windy, as is the case with Santa Anas and other such winds, little can be done to prevent fires driven by the wind from moving unimpeded through chaparral. Aircraft, an important tool in fighting wildfires, may be restricted from flying close to the fire because of high wind velocities or dense smoke that obscures vision.

Houses built on steep slopes covered with chaparral (pl. 76) can be particularly vulnerable in wildfires, because the updrafts of fire bring the scorching air and burning debris straight up the hill to the house. Structures in canyons may be in equal peril during severe fires, because the canyons can act like wind tunnels, funneling the wind-driven flames at hurricane speed. Under severe fire conditions almost nothing can be done to save structures in vulnerable locations. These fearsome blazes cannot be suppressed or even safely approached by firefighters and equipment, either on the ground or in the air.

Plate 76. These houses, surrounded by chaparral, are built on steep slopes with only one access road.

Geographic Risk

There is a degree of geographic predictability about chaparral wildfires and subsequent floods. Certain areas, because of the age of the shrubs, topography, wind patterns, and other factors, are far more likely to experience wildfire than are other areas with lesser or fewer risk factors. Similarly, since water and floods follow the path of least resistance downhill, it is not difficult for an experienced hydrologist to predict how much and where water and debris will be transported when heavy rains fall on recently burned chaparral slopes.

In the 1970s I (R.Q.) used to visit an ecologist friend who lived in the chaparral. His house was tucked into a canyon in the Santa Monica Mountains, not far from the urban bustle of Sunset Boulevard. He lived with his family in a rented house within a California state park. The house was constructed mostly of wood, including a rustic wood shake roof, and it was so intimately involved with chaparral that he ran sensor wires out of the living room and into the adjacent shrubs where he was monitoring the behavior of wood rats. The chaparral was quite old and very thick. The house was accessible only by a single-lane, winding road that made its way up the canyon. We would sit in his living room and discuss what he and his family would do when—not if, but when—the chaparral wildfire came. There was no question that the house would burn if the flames arrived during extreme fire conditions. The house was extremely flammable, and there was no way to safely defend it. Close to the house there was a sort of concrete bunker set in the bank above the stream. It had been constructed for another purpose long ago, but for him it was to be a fire shelter for the inevitable disaster. Three years later that house did burn down, as did about 150 others in one of the periodic wildfires that sweep through the chaparral-clad canyons of the Santa Monicas.

To the unschooled eye, one chaparral area may appear no more or less dangerous than another, but that is not always true. This is why the California Department of Forestry and Fire Protection (2002) has prepared a Fire Hazard Zoning Field Guide that categorizes specific areas of the state according to the wildland fire danger they face. According to this guide, in the year 2000 more than 100 cities and counties contained “very high fire hazard severity zones.” About two-thirds of these were in southern California, and most had chaparral as the underlying cause of hazard. This zoning system allows communities to identify risks to public safety and to take steps to protect themselves, and many towns are doing so.

The most destructive wildfire of its time spread from natural vegetation through an urban area of the Berkeley Hills in 1923. Fueled by a mixture of naturalized eucalyptus trees, grasses, and shrubs, it destroyed 584 structures. A half-century later, fire managers predicted that a very similar catastrophe would happen again because the conditions of wildland fuels and patterns of adjacent urbanization had not improved since 1923. On the contrary, they had become worse. The prediction came true in 1991 when the Oakland Hills fire destroyed nearly 3,000 homes and cost 25 lives, making it the most destructive wildfire to ever occur in California and ranking it as one of the worst natural disasters to ever befall the state.

Floods

In those numerous parts of California where chaparral is located on steep hillsides above urban and agricultural areas, the inevitable fires sometimes bring the subsequent risk of flooding. These are not floods in the usual sense of the word but are more like sudden assaults by muddy slurries that can wreak havoc in a matter of minutes. The relationship between fire and flood is direct but not obvious, and it is often misunderstood or overlooked until it happens. The following sections explain the connection between the two.

Mature Chaparral Acts as a Sponge

The continuous cover of mature chaparral shrubs acts like a vast sponge. Roots hold the soil in place, and the shrubs collect rainfall in such a way that water is gradually and continuously released from the mountains. The tangle of interlocking branches and leaves breaks up and deflects the impact of falling raindrops on the ground, so that the water is scattered and slowed, and droplets are eased into the soil. The layer of leaves, twigs, and other debris dropped from the shrubs onto the soil sets up another series of barriers to the downhill flow of water. The matrix of litter creates tiny dams and obstacles to trickling water, dividing and diverting it into innumerable and circuitous pathways. Robbed of most of its downward velocity and power, the weakened flow seeps into the soil rather than moving down across the surface. While surface water from chaparral-covered hillsides may slowly flow across valleys and out into the ocean, most of the flow is below the surface, collecting in underground basins called aquifers, where it can be tapped long after the rainy season has ended. Above or below the surface, the water can be retrieved, stored, and diverted for future use by humans. Aquifers and local surface water were the sole sources of water throughout California before it was possible to import water from distant sources. Local water originating from chaparral watersheds continues to provide an economical source of much of the water used by people across the arid valleys and coastal plains of central and southern California.

Soils and Heavy Rain

Trouble begins when heavy rain falls upon steep chaparral slopes that have been recently laid bare by fire. Denuded of cover, these once benign and efficient watersheds lose most of their capacity to absorb rainfall. Keen observers long ago noticed that when people walked across the soil of recently burned chaparral vegetation after moderate rainfall, that their boots would turn up dusty footprints. Unlike ordinary soil, these burned chaparral soils were wetted by rain only very near the surface, leaving everything below powder dry. In effect, the fire had somehow waterproofed the soil so that water that could not be accommodated by the top inch or two of soil was forced to run off across the surface. Scientists discovered that the mature chaparral shrubs produce organic compounds with waxlike properties that are deposited on the surface of the soil from litter that falls from the plants. These durable compounds are gradually incorporated into the uppermost layer of soil as the litter decays. When a fire occurs, the waxy substances are heated into gases and driven down beneath the surface of the soil to a depth where cooler temperatures allow them to recondense. There they are concentrated around particles of minerals, creating a barrier to the passage of water as effective as a plastic sheet (fig. 56). Soil scientists call this a hard-to-wet soil.

The extreme heat of many chaparral wildfires, measured in excess of 1,000 degrees F at the surface, incinerates all the organic matter in the upper portion of the soil. This organic component, called humus, binds the mineral particles together like mortar between stones in a wall, and at the same time greatly increases the capacity of the soil to absorb and retain water. Deprived of humus, intensely burned soils lose their internal cohesiveness, becoming as loose and powdery as fine sand. So the burned chaparral hillsides are covered with loose, unstable material with a limited capacity to absorb water, resting upon a layer that actually repels water. Compounding this precarious condition of the soil is the lack of plant cover to mitigate the effect of exposure to the full force of the elements.

Figure 56. Hard-to-wet soil on a chaparral slope. A layer of water-repellent soil develops below the surface after a chaparral fire. While precipitation wets the surface layer of soil, it can penetrate more deeply only through occasional gaps (lower right) in this water-repellant layer. Paths of water are indicated by arrows, and wetted soil is darkly shaded.

Moderate or heavy rain soon saturates the uppermost layer of loose material, which begins to be carried downhill with the water. The heavy, soggy material on the surface slips easily down the surface of the hard-to-wet layer, like wet leaves on a steep metal roof. The water collects into small muddy rivulets, roughly parallel to one another, and cuts a series of rills where the soil has been carried away. The displaced material collects at the bottom of slopes and canyons.

Floodplains

The geology and climate of California have conspired to place many of the most desirable and useful parts of the state in areas subject to periodic flooding. As long as there have been humans in California, they have been attracted to the relatively level places around the aprons of hills and mountains, and the valleys between mountain ranges. These places generally have productive soils and a gentle climate, and when water is nearby, they are eminently suitable for agriculture and settlement. From the foothills of the Great Central Valley to the fertile Salinas Valley, south to the productive Oxnard Plain and teeming valleys of the Los Angeles megalopolis, people are living and working on floodplains, places where over millennia periodic outflows of water and debris from nearby mountains have shaped the landscape.

If all the material carried off slopes by gravity or water were to accumulate and lie at the bottom of hills and canyons forever, neither it, nor the condition of the chaparral above it, would matter. It takes a large flush of water, delivered suddenly, to move the debris out across the valleys. The floods from burned chaparral watersheds are not like those of the Midwest or those that used to inundate parts of the Sacramento Valley. In both of these cases, water slowly and inexorably spreads across gently sloping floodplains as a result of events far upstream. There is time to move people and animals to high ground and prepare for the flood's onslaught. Severe chaparral floods are quite sudden and unpredictable, not gradual. They are akin to the flash floods of Southwestern deserts, which turn previously bone dry washes and river beds into a sea of raging torrents that sweeps away all in its path. The imminent arrival of these muddy floods in the chaparral is sometimes announced by a roaring sound, with the volume and quality of an approaching fast freight train. And there is no more time to escape than to move off the railroad tracks.

A burst of rain near the end of a large storm is the least predictable antecedent of catastrophic flooding from burned chaparral watersheds. This sudden event is caused by a churning at the top of the storm's body, which quickly cools air that is already saturated with water. This turbulent force aloft quickly drives much of the moisture out of the air over one spot, as if wringing out a huge overhead sponge. The physics of this phenomenon is similar to that which generates violent thunderstorms in other climates. Both are relatively brief, localized, quite intense, and unpredictable. They are sufficiently rare as to be unknown to most Californians living in coastal valleys. The downpours can occur upon watersheds covered by chaparral at the middle elevations of mountain slopes that face the Pacific. A burst of rainfall that caused the La Crescenta flood, described below, lasted about 15 minutes, but it came on the heels of a 12 inch drenching. That particular downpour delivered more rainfall in minutes than a typical large Pacific storm produces in 24 to 48 hours. As described in chapter 2, rainfall events like these are unusual, but they are not unprecedented, freakish occurrences. As the pouring rainfall collects at the surface, it gathers a torrent of propulsive force as it is suddenly forced through steep and narrow canyons. The action of this water can grind a house to splinters and tumble crushed vehicles onto roofs in less time than it takes to read this paragraph. Canyons and dry watercourses can be quickly filled with moving slurries of water, mud, boulders, and other debris. These debris flows can scour out loose material that has accumulated in canyon bottoms for decades and then rush at the valleys below with astounding force, velocity, and volume—brown flash floods complete with rolling battering rams in the form of boulders.

The occasional very wet winters that bring floods to California have been a regular feature of the mediterranean climate for thousands of years. We have direct records of these rainy winters since the arrival of the first Europeans who began recording storm events. We have indirect evidence as well for millennia deeper into the past from patterns of flood deposits. Since rainfall records have been kept, we see a number of extreme years. For example the rains of 1862, which continued unbroken for 30 consecutive days, created a lake in the Sacramento Valley that was said to be the size, but fortunately not the depth, of Lake Michigan, leaving the new state capital under water. In another instance, in 1938, a very large flood struck southern California. The flow of the Los Angeles River at its mouth during this flood was greater than the average flow of the Mississippi River at St. Louis. That regional flood killed 119 people, and metropolitan Los Angeles had so much flood damage and standing water that road access to the outside world was cut off for several days. Few years are “average,” but fortunately very few years are so extreme (fig. 4).

It is ironic that mediterranean California, famous for its dry climate, very occasionally experiences rainfall of an intensity seldom experienced in much wetter climates. Even with the steep mountains, and urbanization thoughtlessly placed on the floodplains and in the natural drainages below, it is difficult for people to understand and prepare for an event so infrequent that it is outside the experience of the average resident. Intense rainfall does not occur every winter, or even in every unusually wet winter. Concentration of the rain over a short period of a few weeks, typically caused by a cavalcade of Pacific storms in close succession, produces floods. This pattern is often associated with El Nino conditions that periodically develop in the southern Pacific Ocean.

The Human Reaction to the Variable Climate of Chaparral: The La Crescenta Floods

On New Year's Eve 1933, it had been raining hard for 14 hours in southern California. Late evening parties were interrupted in the La Crescenta Valley north of Los Angeles as the power failed. A sudden burst of rainfall was so intense that water trickled inside buildings through tightly shut windows. Residents inside darkened homes heard an ominous rumble to the north, where the San Gabriel Mountains were disgorging a torrent of debris-laden water from several steep canyons. As the wall of debris cascaded down poorly defined watercourses and spread out across an area of three square miles on the valley floor, the noise of clattering boulders became so loud that conversations inside tightly closed houses became impossible. In 13 minutes the flood killed 49 people and destroyed or damaged 598 homes. Many of the homes were buried to the rooftops, and bodies of some flood victims were never found. They may have ended up in the Pacific Ocean, 30 miles away.

The chain of events leading to this tragedy began with a 5,000 acre wildfire that cleared chaparral from the steep mountain slopes above the valley the month before the storm. Rainfall on New Year's Eve was extraordinarily intense, depositing 12 inches on the bare mountain slopes. Just before midnight the trailing edge of the storm, accompanied by an upper air disturbance, passed across the valley foothills. The disturbance set off a violent downburst of rainfall that lasted about a quarter of an hour. This brief downpour, on saturated soil, set a sheet of water and debris in motion. The burned hillsides were quite steep, and the equally steep canyons held three decades of debris accumulated since the previous floods in 1914. As the rush of water and mud concentrated in these canyons, its velocity and force was amplified. Boulders as large as automobiles were sent tumbling and crashing against one another, driven by the torrent. One of these car-sized boulders was deposited in the middle of Foothill Boulevard more than two miles from the base of the mountains. It was later necessary to blast it into smaller pieces that could be lifted and hauled away.

This storm demonstrated that the La Crescenta Valley could be a hazardous place to live, but this had not been apparent until the unusual combination of a large chaparral wildfire, closely followed by prolonged and occasionally intense rainfall, brought the mountainsides crashing down. To insure that such a disaster would not occur again, natural watercourses were replaced with a system of linear concrete channels to divert water from canyons and slopes so that it would run quickly to the ocean. Debris basins were built in many places at the base of the mountains to confine the boulders, mud, and other materials near the point of origin, so that these materials would not cause damage and obstructions farther downstream. Debris basins look like dams, but they are designed with a different purpose. They stop floodwater long enough for the suspended materials to settle out, and then allow the cleared water to flow out into a flood control channel (pl. 77). When the impounded material fills the debris basin it must be removed by heavy equipment before the next storm deposits more. The La Crescenta system was specifically designed to protect the valley areas from future chaparral fire-flood disasters. Restraint of nature under the engineer's hand was, and is, widely and successfully applied for flood control in the valleys and canyons of California, but this solution is by no means foolproof.

Floods and debris flows still emanate from chaparral, especially after fire, but not on the catastrophic scale that would occur without elaborate flood control works. In 1975 the very same stretch of chaparral above La Crescenta that had burned in 1933 burned again, racing across an area 10 miles wide and 18 miles long in three days, while destroying eight valley homes in a pair of firestorms. The floods came three years later. December 1977 and January 1978 had been unusually wet, but without consequence. Then a huge storm on February 10 dropped 12 inches of rain on the San Gabriel Mountains in a 24-hour period, creating conditions that were an almost exact replicate of those 45 years earlier. It was one of the wettest winters in southern California since recordkeeping began more than a century earlier. Once again, there was a short and furious downpour in the middle of the night, and once again, surges of water and debris barreled down steep slopes and canyons. A new debris basin had been built at the mouth of one small canyon the year after the 1975 fire to contain just such an event, but it turned out to be inadequate.

Plate 77. Aerial view of the debris basin at the mouth of San Antonio Canyon, San Gabriel Mountains. The diagonal gray band across the upper right is a berm that prevents water and debris from flowing out of the mouth of the canyon. The mountains at the top left and below are entirely denuded of chaparral by a recent wildfire. The green at the center is unburned agricultural land, and the light area at the center is a mining operation that processes rocks, sand, and gravel carried to the basin by periodic flooding. The floodplain below the basin is heavily urbanized.

As described by John McPhee in The Control of Nature (1989), at the very moment that basin filled and overflowed with debris, a pair of employees of the Los Angeles County Flood Control District were on their way to inspect the basin, approaching from the road below in a six-ton truck. They jerked the truck around and raced away from the wall of debris that came rushing toward them in the darkness. It caught up with them partway down the hill and spun the truck like a leaf on a brook, with them inside, down toward a slumbering residential street that had suddenly become a raceway for water, muck, boulders, and other objects picked up by the onrushing wave. The truck revolved and caromed off boulders and other vehicles that were being picked up and swept down the street. Miraculously the cab did not fill with water, and the truck remained upright and intact, finally crashing to a stop when it lurched against a tree and concrete block wall. Near where the truck came to a stop, the surge of debris-laden water barreled through, around, and over a house that squarely faced the lower terminus of the street-turned-sluiceway. The front of the house was buried to the eaves by a mixture of mud, rocks, and transported cars. Boulders were deposited on the roof (pl. 78). Several vehicles ended up in the swimming pool, and a sedan was crushed to half its original height and slipped just under the eaves, like a crumpled metal letter being deposited in a mail slot. The onslaught pushed through the windows and nearly filled the house with water and debris. The people inside were floated up on a bed until they could touch the ceiling. The overflow, the wild truck ride, and the flooded house took only six minutes! Luckily the waters receded and there were no further debris flows that year. Both the occupants of the truck and the house survived. The family restored and rebuilt their half-buried home on the same site.

Plate 78. A house buried to its eaves by a giant debris flow in La Crescenta, February 1978. The objects stacked around the tree are flattened automobiles.

Threats to Chaparral

Very Frequent Fire Can Eliminate Chaparral

In a given spot, chaparral wildfires ordinarily occur at intervals of 20 years or more, as pointed out in chapter 3. However the vegetation can burn more frequently, given the proper circumstances. During summer and fall the first year or two after fire, dry and dead herbaceous vegetation from the previous spring can provide continuous fuel that will easily ignite and flash into a fire that quickly spreads between and among resprouting shrubs and shrub seedlings. Although such fires burn with far less intensity than would be the case if the fuel were mature chaparral shrubs, they can spread quite quickly and generate enough heat to kill both resprouting shrubs and small shrub seedlings. Since the immature shrubs have not produced seeds, and the soil seed bank is largely empty, populations of both perennial and annual plants can be depleted or extirpated entirely by such closely spaced fires. Under these circumstances the plant community may be shifted to other vegetation types. Where chaparral grows near the edge of another vegetation type that requires less water, such as grassland, coastal sage scrub, or desert scrub, some elements of these communities may invade and replace chaparral shrub species. Alien species accelerate this process. Sometimes the balance is shifted away from chaparral vegetation incrementally, moving further toward a mix of nonchaparral plant species each time a fire occurs close upon the heels of the previous one.

Invasive Plant Species

In some chaparral locations a regime of frequent fire disturbances encourages the establishment and growth of invasive herbaceous plants native to the Mediterranean Basin, such as bromegrasses (Bromus spp.), wild oats (Avena spp.), mustards (Brassica spp.), filarees (Erodium spp.), and star-thistles (Centaurea spp.). Once these weeds become well established they produce vast numbers of seeds that accumulate in the soil. As soon as winter rains begin, many of these seeds germinate and plants grow densely and quickly, their numbers making it difficult for the seedlings of native species to compete successfully with them for space and light. The establishment of invasive herbaceous weeds sometimes occurs after chaparral wildfires. The weeds displace some of the native herbaceous plants that ordinarily occur after fire. This is particularly true when chaparral grows near places where seeds can spread from established weed populations. Source locations for weed seeds include roadsides, fuel breaks, agricultural and other areas that have been cleared of native vegetation in the past such as pastures and paddocks, and other places subject to frequent human disturbance. As people spread into more and more chaparral areas, they create centers from which invasive plants can spread into chaparral following fire. These new vegetation types, often dominated by a handful of exotic weed species, are of lower stature, provide much less erosion control and capacity for water retention, contain far fewer species of native plants, and are far less valuable as habitat for native species of animals than the chaparral vegetation that they displace.

A number of species of shrubs from Mediterranean Basin ecosystems have been deliberately planted in California. Since their introduction, they have moved into the chaparral in many parts of the state, where they now are reproducing and spreading on their own. These shrubs were introduced for variety, color, slope stabilization along roadsides, and fire control. Since they evolved in a similar climate and many are tolerant of poor soils, they grow well in California without attention. Introduced shrubs now growing wild in California chaparral include rock-roses (Cistus spp.), rosemary (Rosmarinus officinalis), and three species from the legume family—Spanish broom (Spartium junceum) (fig. 31), Scotch broom (Cytisus scoparius), and French broom (Genista monspessulana). The brooms are classified as noxious weeds by the California Department of Food and Agriculture because they have taken over many chaparral areas, especially in disturbed habitats, and are excluding the native plant species. The tree of heaven (Ailanthus altissima) is becoming increasingly common in chaparral and elsewhere in California. Originally brought from Asia during the Gold Rush, it spreads and grows quickly from seeds and by root sprouting and may exceed 50 feet in height. It does well among and adjacent to chaparral shrubs, especially in disturbed areas. Because of its height, ability to spread, and tolerance of harsh conditions, it could easily displace chaparral shrubs as well as many other native vegetation types on a wide scale.

Global Climate Change

The changes in global climate predicted by the overwhelming majority of scientists will surely alter the distribution and condition of chaparral, other ecosystems in California, and the economy and life of people everywhere. It is difficult to predict with accuracy the exact nature and magnitude of these changes, but a number of general trends seems clear. During this century California is expected to become somewhat drier, much hotter in summer, and warmer in winter. A greater fraction of precipitation will probably be delivered by intense winter storms. Extreme summer heat and aridity could foster more frequent large and destructive chaparral wildfires. These fires could be followed by serious flooding if winter storms do indeed become more severe.

The combination of less precipitation and higher temperatures would favor the spread of drought-tolerant grasses, especially invasive alien species that carry frequent fires, as described above. Under this scenario a large fraction of chaparral and other shrublands across the state would be converted to grass. There could be a general shift in the range of remaining chaparral to higher elevations, moving into mountainous areas now occupied by forests and woodlands. The assemblages of populations of plants and animals in chaparral and many other ecosystems would be disrupted and rearranged, because different species would have varying abilities and opportunities to migrate to new areas quickly. The complex mosaic of vegetation types that has remained relatively stable in California for thousands of years would be disrupted. Isolated patches of chaparral now containing narrow endemic species, such as maritime chaparral in the south and serpentine chaparral in central and northern California, could easily vanish because of the lack of a nearby suitable habitat. In general a minority of species of chaparral plants and animals that are most adaptable and mobile would be expected to become more numerous and widespread, while the majority of species less able to respond to rapid change could become less common or extinct.

Options for Wise Growth

Catastrophes born out of chaparral wildfires and floods are predictable in the sense that floods from rivers and death from disease are predictable. No one can foretell exactly what is going to happen, or where and when, but by understanding the factors that underlie risk, it is possible to estimate probability and to reduce that risk through proper preparation. The balance of this section is about how to reduce the chance of loss by chaparral wildfire through informed preparation.

Many people, including myself (R.Q.), choose to live near chaparral. While writing this book a chaparral wildfire came within a block of my house, and 65 homes in my city were destroyed in a few hours (pl. 79). The motive for living in such a place is often the desire to be close to nature and enjoy the daily pleasures of observing the workings of nature. As more and more people have exercised this choice, the associated dangers have grown many times over. From the foothills of the Sierra to the narrow canyons of the Santa Monica Mountains, ex-urbanites choose to live surrounded by nature. The relentless pressure of general urban sprawl compounds this trend. From the outer ring of suburbs of the Bay Area to the scenic cities of the Central and South Coast Ranges and on to metropolitan Los Angeles and San Diego, human development of all kinds spills up and into chaparral. Given present planning practices and economic forces, this is the path of least resistance for horizontal growth. So long as the human population of California continues to grow exponentially, as it has done for the past 150 years, the forces that have pushed development into chaparral will continue. While this spread is regulated to some degree by government planning agencies, urban growth of this kind is driven primarily by demand for inexpensive space for new homes and businesses. Some planning generally accompanies this growth so that basic needs such as roads, schools, water, and the numerous other elements of urban infrastructure are there to meet the needs of new residents. One part of the planning process is public safety, including protection from wildfires and flooding. However, this is rarely accorded as much attention as the more familiar details of roads and schools.

Plate 79. A neighborhood adjacent to chaparral, with homes that were recently destroyed by wildfire.

If the planning process were perfect all new residents near chaparral could be assured that they were reasonably safe from the hazards of wildfires and floods. These risks are only two of many factors that are considered when buildings and subdivisions are planned and approved. Well intentioned as the entire process might be, the seemingly remote possibility of a wildfire or flood is usually not the first consideration of people who propose developments, public agencies that approve the proposals, or people eager to move to a serene hillside or canyon with an unobstructed view of natural vegetation and wildlife. Moreover, older developments often do not adhere to today's building and planning standards, but there they stand. So wood-sided houses with shake roofs are tucked into canyons, chaparral and other flammable vegetation grow right to the edge of buildings, homes with unenclosed wooden decks hang out over the edge of chaparral-covered slopes, access roads are inadequate, and innumerable other hazards exist that would not be permitted in most jurisdictions under today's laws and regulations (fig. 57).

Historical circumstances and inadequate planning can be partially overcome, reducing the danger for the current residents. Property owners in established areas can be informed of hazardous conditions and be encouraged or even required to make changes. For example, when replacing a roof or preparing a personal emergency plan, residents can take into account likely wildfire patterns and the potential for flooding that may result. The family eager to build a dream home in the mountains can, and often is required to, have a driveway suitable for emergency vehicles, have roofing material that is not readily flammable, and clear away native vegetation to specified distances from structures. After the chaparral wildfires of 2003 in southern California, written notices were mailed to 113,000 residents of San Bernardino County warning that flash floods were likely with little or no warning with each storm. These warnings were issued after a heavy rainfall, and a flash flood on Christmas afternoon had taken the lives of 16 people. People can be provided with expert advice about how to live as safely as possible with chaparral. Beyond that, however, individuals are usually free to make private decisions about how to use private property.

Figure 57. Chaparral wildfires move rapidly upslope, quickly engulfing and destroying overhanging structures too close to the edge and to the burning shrubs.

Individual homes that do not comply with fire-safe practices can endanger their neighbors. It is common for a single house with a flammable roof or poor clearance from natural vegetation to ignite first during a wildfire and then provide the heat and firebrands that set fire to neighboring structures.

Planning for Chaparral Safety

The larger issues that are concerned with regional public safety near chaparral are more difficult to address. These have to do with ingress and egress during large wildfires, the modification of natural vegetation, construction and maintenance of flood control facilities by public agencies using public money, and the availability and coordination of emergency workers and equipment during disasters. A chaparral landscape that is unpopulated is far easier to deal with during a wildfire or flood than the same landscape when it is studded with scattered dwellings without emergency water and accessible only by long, narrow roads.

About half of California chaparral is located on public lands, primarily in national forests, but also in other federal, state, and local government jurisdictions. When U.S. Forest Service boundaries were delineated more than a century ago, they were drawn to exclude land that was already in private hands. Consequently, the boundary lines are often quite irregular and often include islands of private land, called inholdings, inside national forests. The designation and acquisition of state lands, railroad lands, and other ownership transactions in the nineteenth century sometimes created equally fragmented boundaries between private and public land. More than a century later these lines have often become the hard, jagged boundary between chaparral and spreading urban areas. People build up against the public land, often quite intentionally, knowing that the open space beyond the backyard will remain open forever. Private inholdings are often the location of small, concentrated resort settlements that rely on the surrounding public land for recreation, water, access, and other resources and services.

This broken pattern of private-public land ownership and attendant use near cities has created a ragged and often abrupt boundary between civilization and nature. This edge is referred to as the urban-wildland interface. Such complex landscapes make it difficult to cleanly and safely separate and protect urban areas from wildfires. The neighborhood shown in pl. 79 is surrounded on three sides by expanses of chaparral, with additional flammable vegetation to the south (upper right) and between the rows of houses, which are arrayed on steep slopes and ridge tops. Weeks before this aerial photograph was taken a chaparral wildfire, driven by a severe Santa Ana wind, and firestorm approached from the east (right), burned around and through the neighborhood by following the natural and planted vegetation, and continued to the west. As is usually the case, those structures closest to the chaparral and those at the edges of steep slopes were most vulnerable. Fifteen homes were destroyed and several others damaged in a very short period of time.

Often the most practical way to increase safety at the urban-wildland interface is to reduce chaparral fuels on land that is near built up areas. Fuel breaks have been constructed for this purpose in all parts of California. Thoughtful planning of new development at the urban-wildland interface could focus on straightening out the line between chaparral and development, either by keeping structures at a uniformly safe distance from natural vegetation or perhaps by land exchanges between private and public owners. The belt of private and public land that should not have permanent structures or wildland fuels could be used for many other desirable purposes such as parks, open space, golf courses, row crop agriculture, trails for hikers, horses or bicycles, or any other use that does not entail placing flammable permanent structures close to chaparral.

The looming danger of wildfire catastrophes has steadily increased from one end of California to the other. Annual losses of lives and property from chaparral wildfires have been increasing for close to a century. The problem will continue to grow worse as long as current patterns of scattered and disorganized growth are extended ever farther into wildlands. We have ample evidence every fire season that under extreme fire conditions it is sometimes impossible to protect all lives and property from chaparral wildfires. There are several ways to reduce this danger. First, as described above, chaparral fuels can be managed in key areas. Second, settlements and structures can be made as fire safe as possible by properly designing structures and providing adequate vehicle access and emergency water sources. Third, new structures and communities can be situated in places that can be made relatively safe and can be protected by available firefighting resources. This would probably mean that new and growing towns near chaparral would have to be more compact, a recommendation that runs counter to present trends almost everywhere in California. Over the long run, better planning is the most important measure to make people residing near flammable wildlands safe.

The Public Cost of Private Decisions

Some people choose to settle in particular places with full knowledge that they have selected a spot that is at high risk of experiencing chaparral wildfires. These people sometimes argue that they have the right to assume such a personal risk. However, in the event of a fire, the safety of these individuals and their dwellings suddenly becomes a matter of public concern and expense. Residents of high-risk areas, sometimes with hazardous homes and grounds that do not follow fire-safe practices, expect the same level of emergency protection as everyone else, at public expense and often real personal risk to firefighters. When structures in dangerous places are insured against fire, they may be placed in a high-risk pool, where the full cost of the actual risk is not directly assumed by the owner. After structures are damaged or destroyed by wildfire, the victims are sometimes offered state and federal disaster relief. Assistance in the form of low-interest loans, temporary relocation expenses, and other services often supports and encourages people to more easily rebuild in the same location. These actions arise from the natural desire we all feel to help people who have had their lives disrupted by sudden and unexpected catastrophe, but it must be kept in mind that the result may be to perpetuate and subsidize settlement patterns that are inherently dangerous. It is common to require that replacement buildings be constructed with materials and in ways that are more fire safe than the originals. Over the long run, society as a whole might be better off to go a step further and entirely eliminate incentives for living in places where future fire disasters are likely. As city, county, state, and federal budgets become more and more strained and stretched, it is imprudent to allow private landholders to bill the ultimate cost of their private decision to live in a hazardous area to the rest of us. That decision is not private, and it is expensive.

One safety measure that is commonly imposed on isolated communities and homes near chaparral is to require the clearing away of native shrubs and other flammable vegetation for distances of 30 to 200 feet around all structures. This removal is important and relatively effective, but it entails replacing chaparral with other types of vegetation that are probably not native to the site. In some circumstances, where clearing is poorly planned or maintained, these places can become footholds where invasive weeds become established and spread. As more and more structures are placed in chaparral vegetation, with a cleared perimeter around each, as well as cleared strips along access roads, the carpet of continuous natural shrub cover becomes more and more tattered and disconnected. Necessary as it is, the practice of brush clearance for fire safety diminishes the ecological integrity and value of remaining disunited chaparral landscape as habitat for native species of animals, and it certainly alters the aesthetics of the increasingly unnatural landscape.

In the final analysis, Californians must decide together how much of the chaparral community we wish to retain as part of our natural heritage, recognizing that such places will always be subject to periodic fires. There is ample legal precedent for setting standards to protect and conserve the beauty that emanates from chaparral and other natural vegetation. Government everywhere already places numerous restrictions on how private property may be used in the form of zoning laws, as well as ordinances specifying aesthetic standards for many things including natural and ornamental vegetation. In many communities particular species of native trees, such as oaks, may not be harmed or disturbed on private or public property, and streamside vegetation is often protected in the interest of water quality, native fish and other aquatic organisms, and of course natural beauty.

Any seasoned firefighter can explain what precautions should be taken to reduce the probability of losing a structure to a chaparral wildfire. Most of these measures can be reduced to three categories: accessibility, defensible space, and fuel management. Firefighters arrive in fire trucks and other large emergency vehicles, often under chaotic circumstances. Street addresses should be clearly and conspicuously marked. The roads leading to the threatened structures, including private driveways, should be wide enough to permit emergency vehicles easy access. Often, emergency vehicles must reach threatened structures at the same time frightened people are attempting to depart by the same roadways. Structures near chaparral, especially houses and barns, are much safer with at least two access roads. That way if an approaching fire blocks one escape route, another can be used.

Defensible space is an area around a structure, cleared of hazardous fuels, that is large enough to place safety personnel and firefighting vehicles between the fire and the building. Hazardous fuels include buildings, attached structures, and outbuildings made of wood and other flammable materials, ornamental plants that easily burn, wood piles, automobiles, and anything else that could quickly catch fire when subjected to a sudden blast of heat, wind, and flames.

Fuel management includes a choice of building materials and architecture that makes a structure less easily ignited from the outside. The single most vulnerable point of ignition for a structure is the roof. It receives direct exposure to approaching heat and flames and is the place where burning materials carried through the air can land and start a fire. Fuel management also includes choosing ornamental vegetation of low flammability that separates, rather than connects, a structure with surrounding wildland fuels. Another very important aspect of fuel management is the chaparral itself, which should be cleared away from all structures and access ways to safe distances, equaling or exceeding those required by ordinance.

Detailed advice on planning and preparedness for wildfire emergencies is available free of charge from the California Department of Forestry and Fire Protection, the USDA Forest Service, the University of California, and various county and local governments. The Fire Safe Council provides guidance for communities. Booklets, pamphlets, brochures, on-line materials, and other resources are often free for the asking.

The Value of Chaparral

Why should we care whether the chaparral exists or not? Why should humans not simply replace the plant and animal world with the human and concrete world? If they could speak, the plants and animals could tell us what it takes for sustained life here. From studying the natural life of the chaparral we will learn lessons about careful use of water, protection of the soil by deep roots, and conservative use of resources.

By following the natural patterns of chaparral, the wasteful and often unsuccessful practice of emulating the vegetation of an English garden could be replaced by sustainable, feasible gardening methods. Rather than bright green lawns surrounded by soft-bodied, water-guzzling plants, Californians would use drought-tolerant plants to create their gardens. Xeriscape landscaping, which employs plants that grow well in dry conditions, is becoming increasingly popular, both to conserve precious water and for the natural beauty of plants native to California and other climates with dry summers. Mediterranean Europe and Australia are sources of some truly drought-tolerant plants such as rock-roses (Cistus spp.), rosemary (Rosmarinus officinalis), oleander (Nerium oleander), and a host of others. These plants are adapted to a mediterranean-type climate and thrive in Californian gardens if they are not overwatered. The chaparral's native manzanitas (Arctostaphylos spp.) and ceanothus (Ceanothus spp.), toyon (Heteromeles arbutifolia), and cherries (Prunus spp.) also make attractive garden additions. Xeriscape landscaping is relatively easy to care for, requires far less water than traditional ornamental plants, usually requires less attention to the soil, and provides a wide variety of colors and textures. Wisely chosen plants in a carefully planned garden also create a buffer of low flammability around structures.

Chaparral shows us that it is not only possible to live with fires, droughts, and floods, but that life can flourish in spite of these “disasters.” Water is always going to be a problem in a mediterranean climate. There is not enough of it to go around in California, so we need to use less and conserve more. We can appreciate that the fires that do happen are natural and life giving to the chaparral. They do produce smoke and blackened hillsides, but they also release an entire generation of wildflowers from their underground imprisonment by the shrubs above. Fires also give the shrubs a chance to renew their growth and expand their especially capable root systems. It is often best to leave these shrubs alone, not to bulldoze, bully, or change the chaparral into something else. Chaparral shrubs usually grow on poor soils and often on steep slopes, far from water, that are not well suited for other purposes. These shrubs stabilize the soil, provide lovely views, and keep the environment cooler and moister than it would ever be if cleared. There are other kinds of lessons to be learned from the animals that make chaparral their home. The efficiency of insulation and the intricate cohabitation of organisms in a wood rat (Neotoma spp.) nest are remarkable. Maybe within this complex is a new design for human habitations that is more efficient and ecologically sound than what we have so far devised. Clearly, we don't want to live in a pile of fuel as they do, but the nest form itself may contain some useful but as yet unrecognized principles of design. We can also appreciate that sooner or later, steep slopes and poor soils are likely to result in substantial erosion and mudslides and choose not to live in a place that is in the path of such hazards. We can use the sun to warm our homes, like the harvester ants (Pogonomyrmex spp.), to an even greater degree than we are already doing. Like lizards and snakes, we can power our actions with sunlight's energy, too. We can learn the intricacies of our environment so that like a Wrentit (Chamaea fasciata), we find a full life within the environment we create. We need to do a better job of taking advantage of natural processes, rather than ignoring or opposing them.

For California, the future of chaparral and our future as residents here are inextricably linked. Much of the remaining privately held natural land near the growing population centers in central and southern California is chaparral and coastal sage. The rate of land development of these areas in the past decades has been, and continues to be, astonishing. Everywhere we see new housing tracts, shopping malls, and freeways being built as more and more people occupy what was once “empty” land. With this rapid spread of human settlements in California, chaparral and other natural ecological communities are in great danger of incremental destruction. The hardy plants and animals are not preadapted to bulldozers and cement. For plants and animals, sunlight, water, space, and nutrients are required for abundant life. Obviously, these simple requirements are lacking entirely under sidewalks, buildings, and highways.

Sooner or later we must strike a deliberate balance between the spreading urban and ex-urban centers of California, and the adjacent chaparral in their path. Half of the remaining chaparral is on private land and consequently available, at least in principle, for urbanization. In addition to the natural services chaparral performs free of charge, it has always been a beautiful backdrop to life in California (pl. 80). Urbanization cannot continue to consume chaparral and other natural areas indefinitely, and few people would wish to see all of the remaining natural beauty of this exceptionally attractive state that falls outside of existing reserves consumed by development.

Chaparral has already survived many thousands of years in a demanding climate of droughts, fires, floods, heat, and cold; but the inexorable pressure of human encroachment may ultimately be a much more serious challenge. If we decide to retain as much chaparral as possible now, the plants and the animals will survive, and human Californians will benefit as well. We will continue to be surrounded by a healthy, strong, natural community that has many lessons to teach us. The vertical leaves of manzanitas may thus continue to provide for life and energy in a climate so dry most plants would perish. The roots of ceanothus, with their nitrogen-fixing bacteria, could continue to enrich the soil and beautify the landscape. And the hundreds of thousands of wild flowers, shrub seedlings, and resprouts and the myriad of animal inhabitants large and small would flourish to let us know that life is revitalized after fire. The chaparral is ours too, and it is a rich legacy.

Plate 80. Chaparral provides scenic hillside beauty throughout California.

Chaparral does more than provide useful lessons and natural services. The ever-changing beauty of the chaparralcovered hills offers a much-needed respite from the glare of concrete and the frenzy of congested urban areas. The Hollywood Hills are famous but would hardly be improved by being entirely covered with concrete or skyscrapers. The chaparral behind and above the Hollywood sign is an essential part of its charm. The appeal of chaparral grows with familiarity. The undulating blanket of shrubs, the kaleidoscopic mosaic of flowers in spring, the carpet of wildflowers the first few years after fire, and even the pungent odors of laurel sumac (Malosma laurina) and other chaparral shrubs that fill entire valleys on hot summer days—all of these are parts of the natural heritage of our state that are worth saving for the future. Hillsides clothed in chaparral remind us on a daily basis of where we live, and of what it means to be Californian. The solid and durable chaparral is a reflection of the beauty, promise, and enduring spirit that continues to attract people to the state.