Introduction

Woody vegetation in these regions displays a number of typical xerophytic adaptations to the summer drought: reduced leaf size, coriaceous or sclerophyllous leaves, oily or waxy leaves, dense and thick bark, deep root systems, and the capacity to stump sprout after fire. The vegetation is capable of tolerating fires, which often take place in late summer or early fall with the advent of desiccating adiabatic winds coupled with ignitions set off by lightning or by human activities. Many species rely on stump sprouting to recover from fire, but fire-dependent germination is utilized by many species to ensure optimal survival conditions for seedlings.

One of the Mediterranean vegetation formations is the Mediterranean scrub, variously known as chaparral (California), maquis, garrigue, phrygana (Mediterranean), fynbos (South Africa), matorral (Chile), and mallee and kwongan (Australia). This is a shrub-dominated formation, typically ranging from 0.5-4.0 m in height and generally forming a dense cover with nearly 100% ground cover and leaf area indices around 2. While Mediterranean scrub species can generally grow in a variety of soils, it competes best on steeper slopes with coarse, unstable, and poorly profiled soils. As such, it can be found on steep slopes from 400-2,000 m.

The similarities among the various Mediterranean scrub formations around the world has not led to similarity in interpreting them among the biogeographers, ecologists, botanists, and foresters dealing with them in the different Mediterranean regions. The purpose of this paper is to establish the differences in interpretation between the American and the European traditions in these fields, with an eye towards the differences in fire hazard management they imply.

The Literature of the Mediterranean Scrub

Succession in Mediterranean Landscapes in the European Tradition

In European writings, Mediterranean scrub is commonly described as degraded secondary successional formations that express the negative impact on the landscape of thousands of years of human activities: deforestation for agricultural clearing or for timber, overgrazing or overbrowsing by livestock (notably goats), and by wanton use of fire for clearance and convenience. The regional "climax" vegetation is characterized as oak-dominated forests and woodlands, which hang on as relict stands in a few scattered areas.

A popular British textbook in physical geography, Smithson, Addison, and Atkinson, Fundamentals of the Physical Environment, 2nd ed. (2002), puts it this way (p. 524):

In all Mediterranean regions much of this woodland has been replaced by agricultural land, originally for the traditional dry-farmed crops of cereals and tree crops (e.g., the vine, olive, carob, almond), but increasingly for high-value irrigated land use (e.g., vegetables, citrus fruits, rice). Outside the limits of farmland, human impacts on the natural vegetation have been severe, mainly through grazing, ranching, wood collection and deliberate firing. The native woodland has therefore been replaced by dense scrub...

Nowadays there are only a few remaining places, in the mountainous regions of North Africa, where typical Quercus ilex forest still exists. Elsewhere the trees are cut down every 20 years, while still young, and they regenerate by means and (sic) shoots from the old stump. This leads to the formation of a maqui, consisting of bushes the height of a man. Maqui is also encountered on slopes where the soil is too shallow to support tall forest. Sclerophyllous species, usually shrub-like in form, may develop into big trees in a suitable habitat and can achieve a considerable age. Imposing old specimens of Quercus ilex can be seen in gardens and parks. In places where the young woody plants are cut every six to eight years and the areas regularly burned and grazed, the trees disappear entirely and open societies called garigue are formed (phrygana in Greece, tomillares in Spain, batha in Palestine)....If cultivation or grazing is stopped then successions tending towards the true zonal vegetation take over

Mediterranean regions have long been impacted by humans especially through the use of fire and the grazing of livestock. The Mediterranean proper, we know from classical Greek literature, was formerly forested with live oaks, pines, cedars, wild carob and wild olive. The shrublands of California, likewise, are believed much more extensive today than before aboriginal burning and Spanish livestock grazing. ...

The Mediterranean proper--Europe, North Africa, and Asia Minor: around the Mediterranean Sea, which penetrates deeply into the Old World land masses, the biome reaches its maximum extent. Much of the formation is considered a subclimax developed on degraded and eroded soils and maintained in part by fire and goats. It is from this region that many culinary herbs associated with Italian cuisine originate. The shrublands are known locally as maquis.

The maquis and garrigue vegetation has evolved over thousands of years in an environment of heavy grazing and frequent cutting and burning

..the outlines of the story of how the prehistoric Mediterranean woodland forest was destroyed has begun to come to light. This story begins with mention of the burgeoning evidence for the beginnings of agriculture in the Near East having occurred in the Mediterranean forests of the Southern Levant. The discovery of forest-dwelling Epipalaeolithic cultures associated with this achievement in the Hisban Region is consistent with other findings that point to the existence of a Mediterranean Woodland Forest here during Early Holocene and Neolithic times.

Has the frequency of fire produced the presence of the shrublands or has the existence of the shrublands allowed the occurrence of repeated wildfires? Is this type of vegetation due to wildfires or does the vegetational type induce wildfires? Or is it a question of both processes acting synergetically? ... Another question: why, throughout the area without fire disturbance, has a progressive dynamics not followed its "natural" process, with a reversion to primeval forest? With or without fire, communities and landscapes have not reached a stable equilibrium.

Most Mediterranean countries regard themselves as ruined landscapes, "degraded" through thousands of years of misuse of the land, which might be "restored" to the forests supposed to have existed in an idealized past.

Chaparral in the American Tradition

A different impression is conveyed in American literature. In this tradition, chaparral is described as one of the "climax" formations that develops in Mediterranean climate rigimes under slope, edaphic, and fire conditions that give it the competitive advantage over oak park and woodland, mixed woodland, California prairie, or coastal sage/soft chaparral. This is not to overlook the anthropogenic impacts in Mediterranean ecosystems, but the premise is that the formation itself is a natural element of the landscape.

For example, in a common American introductory physical geography textbook, Essentials of Physical Geography, 3rd ed. (1987), by Gabler, Sager, Brazier, and Wise, the flavor of this perspective comes through (p. 276):

The general look of the vegetation is a thick scrub, called chaparral in the western United States and maquis in the Mediterranean region... Wherever moisture is concentrated in depressions or on the cooler north-facing hills slopes, deciduous and evergreen oaks occur in groves. Drought-resisting needle-leaf trees, especially pines, are also part of the overall vegetation association. Thus the vegetation is a mosaic related to site characteristics and microclimate.

The typical vegetation structure of the Mediterranean biome includes a mosaic of valley forests, open woodlands, shrublands, and grassland. ... The distribution of woodland, shrubland, and grassland can reflect a number of factors, including regional rainfall differences, slope aspect, substrate, and disturbance. In regions where annual precipitation is less than 40 cm there is often insufficient deep percolation of water to support deep-rooted shrubs In these areas small shrubs, annual plants, and grasses predominate. Fire is common during the long dry summers and can restrict shrub and tree dominance. In addition, it is thought that some of the extensive shrublands around the Mediterranean Sea are the result of overgrazing by goats and other livestock, followed by erosion of the topsoil.

Mediterranean regions are found in the countries of Europe, Africa, and Asia that border the Mediterranean Sea; in southwest Australia and South Africa; and in Central Chile, Mexico, and the State of California. The climate is characterized by hot, dry summers and wet, moderate winters, Rainfall ranges from about 10 inches (250 mm) to above 32 inches (800 mm). The mixtures of plant species within these areas are determined by such factors as aspect and steepness of slope, soils, elevation, fire frequency, and local climate.

Major plant communities form broad zonal belts that increase in elevation southward into Baja California. Grasslands and coastal sage scrub in lower coastal valleys are replaced by chaparral on mesic coastal slopes of the mountains. Mixed evergreen forest and mixed conifer forest occupy the highest mountains and grade into pinyon and juniper forests and various scrub communities on the east slope of the mountains adjoining the Sonoran and Mojave deserts.... Grassland, coastal sage scrub, and chaparral, in which nearly all the burning detectable by Landsat imagery occurs, are divergent in terms of physical appearance, rooting structure, phenology, drought stress, fuel, and fire response.

There are many misconceptions about the relation between California chaparral and fire. One is that primeval forests were open and park-like, and brushy areas were small and insignificant until white men (sic) settled California. (p. 29)

The successional status of chaparral has been debated for years, some botanists even questioning whether chaparral is a climax association. Clements' (1916) early writing considered the California chaparral a deflected or altered vegetation.... Other botanists have rejected the hypothesis that chaparral is a fire subclimax, proposing that it is a true climatic vegetation (Cooper 1922, Bauer 1936, Munz and Keck 1959). (p. 30)

In Clements' later writings (Allred and Clements 1949) he also recognized chaparral as a true climax that persisted after recurrent fires (p. 31).

A Shifting European Perception of the Human Rtle in Mediterranean Scrublands

As seen in the Trabaud and Galtii and Rackham excerpts, there is a new skepticism within the European tradition towards the rigidity of interpretation of the Mediterranean scrub. A factor driving this re-examination is the increase in large fires coonciding with the abandonment of Mediterranean agropastoralism with the globalization of economic competition and the increase in home construction in fire-prone amenity areas.

Rackham (2003) puts it:

There is abundant reason why fire should have increased. There is now much more to burn than when the countryside was densely populated and used. Abandoned farmland or neglected pasture turn into forest or shrubland. They are invaded especially by pines and Cistus, which happen to be among the most fire-promoting genera in the European flora. Moreover, natural vegetation used to be interspersed with fields and vineyards which acted as fire-breaks. When these are overgrown, fire can spread much farther before it meets an obstacle.... Foresters promote fire in another way, when they exclude browsing animals and thus allow native vegetation (especially grasses and shrubs) to grow up and accumulate fuel.

In countries on the northern Mediterranean basin, the collapse of the age-old agrosilvipastoral system is leading to deep changes in the structure and architecture of forest and pre-forest communities of plants and animals and, in general terms, to an aging of forest populations (Barbero et al., 1990). ... Although the ecological and socio-economic processes vary from region to region, the resulting ecological consequences are very similar: i) disruptions in the natural cycles of disturbances and ecological imbalances, causing large-scale climatic catastrophes; ii) a homogenization of the structure and architecture of plant communities; iii) a marked loss in biological diversity and the banalization of flora; and iv) the spread of immigrant species through "artificialization" of environments that pose competition to indigenous plants in the undergrowth as well as in upper storeys.

The maquis and garrigue vegetation has evolved over thousands of years in an environment of heavy grazing and frequent cutting and burning but agricultural land use in the Mediterranean has changed considerably in the last 20 - 30 years. Records show that grazing of semi-natural Mediterranean vegetation by sheep and goats has virtually ceased in several European countries where marginal land has been abandoned. This has lead (sic) to the rapid succession to woodland and accumulation of biomass. This in turn then affects the frequency and intensity of fires. Abandonment of traditional land management will result in dramatic changes to the landscape.

Despite conducting this study based on pollen data we have identified ecologically plausible trends in the abundance of traits along climatic gradients. Plant traits other than the usual life form, leaf type and leaf phenology carry strong climatic signals. Generally, combinations of plant traits are more climatically diagnostic than individual traits. The qualitative and quantitative relationships between plant traits and climate parameters established here will help to provide an improved basis for modelling the impact of climate changes on vegetation and form a starting point for a global analysis of pollen-climate relationships.

The American Debate over Chaparral Fire Dependency Heats up

The European literature is not alone in re-assessing its assumptions. In the American literature, however, the focus is not on the naturalness of chaparral but on the rtle fire plays in vegetation succession. The oldest writings on California chaparral followed European disparagement of the scrublands, giving way to a more empirically-grounded view as early as the 1920s. Much attention began to focus on adjusting the climax vegetation concept to accommodate the kind of seral mosaic landscape produced by this vegetation that adapts to and exploits fire disturbances associated with the summer drought climate.

An entire school of thought grew up around the reconceptualization of chaparral as pyrogenic, not just adapted to fire but actually dependent on it and capable of producing the conditions that enable fire. Examples of writings in this vein include:

Hanes (1971), for example, concludes:

Chaparral fires are both natural and inevitable. A fire-exclusion policy does not prevent fire, it only forestalls fire. In chaparral stands where fire has been excluded for decades, the threat of fire is greatest. ... It is possible that, in terms of preserving the chamise-chaparral of southern California, long-term fire exclusion might be the least desirable practice.

Stands as old as 20 years contain little dead fuel and are thus relatively nonflammable ... Stands older than 30 years show signs of stagnation owing to diminished nutrient cycling..., leading to increased dead fuel content in the canopy, litter, and duff (50 to 70 percent of biomass). Chaparral therefore becomes especially flammable after 30 to 50 years, depending on climate and local fuel accumulation rates (p. 1290).

The present regime of large, intense conflagrations in southern California chaparral appears to be an artifact of fire suppression. The great achievement of suppression is the extinguishing of small fires....Thus prevention efforts by a few forest rangers and settlers between 1880 and 1910 may have interrupted burning enough to erase some of the presuppression mosaic. Since 1910, small fires have been replaced by ever-larger ones, with numerous conflagrations since the 1950s despite increased suppression investment. Indeed, the present mosaic in southern California is capable of supporting even more enormous fires, possibly as large as 100,000 ha...(p. 1293).

The steady accumulation of fuel is the mechanism by which chaparral creates a condition on which it depends. As a result of this accumulation, the longer the period since a fire, the greater both the probability and the magnitude of the next fire.

This view has recently been challenged. A number of studies have directly questioned whether fire hazard in chaparral is dependent on the age of the stands and whether large fires have, in fact, actually increased in frequency in the wake of fire suppression.

Paleoecological records reveal that these large fires driven by Santa Ana winds were a prominent feature of the landscape long before European settlement. ...The contemporary fire regime in southern California shrublands mirrors the natural fire regime much more closely than is generally credited. ...As is the case today, the natural fire regime was likely characterized by many small fires and a few large fires that consumed the bulk of the landscape. ... The primary change in the fire regime has been the marked increase in fire frequency in areas of high population density such as southern and central coastal California. ... Today, fire suppression is required just to maintain some semblance of the natural fire regime.

Large fires in chaparral-dominated shrublands of southern and central California are widely attributed to decades of fire suppression. Prehistoric shrubland landscapes are hypothesized to have exhibited fine-grained age-patch mosaics in which fire spread was limited by the age and spatial pattern of fuels. In contrast, I hypothesize that fires during extreme weather conditions have been capable of burning through all age classes of the vegetation mosaic. ... Exposure to extreme fire weather therefore appears to override the sensitivity of a fire regime to fuels characteristics at the landscape scale. ... Findings contradict the assertion that, in the absence of fire suppression, large fires would be constrained by more complex age-patch mosaics on the landscape.

It also entails a massive social subsidy: The firefighting taxes and insurance assigned risk pools represent the socialization of household-level risk assumption.

As Rodrigue (1993) puts it:

Consideration of chaparral fire hazard in the Santa Monica Mountains suggests that the benefits of an amenity view are privatized, while the private hazard costs to the household are reduced by the socialization of fire hazard mitigations. Household benefits seem higher than household costs, thus encouraging action on environmentally dysfunctional landscape values if households have the resources to act on them.

SIAM assesses the potential for structure ignitions from wildfires burning in vegetation and other structures. SIAM is based on the premise that structure survival is the essence of the W-UI fire problem, but structure ignition is the critical element for survival. Thus, the model specifically addresses the potential for structure ignition rather than the potential for structure survival (p. 21).

Additionally, experiments and model results indicate that flames are an ignition threat only at close distances to a structure. ...This finding suggests that nearby landscape vegetation and neighboring structures are important factors in structure ignitions. However, structures commonly ignite when fires are at distances too great for flame-heated ignitions, suggesting that firebrands are an extremely important source of ignition on and adjacent to a structure. Vegetation management beyond the structure's immediate vicinity has little effect on structure ignitions (p. 22).

Conclusion: Toward Reconciliation?

First, the European tradition needs to resituate Medterranean scrub as a natural formation as validly present in the Mediterranean borderlands as woodland and forest but adapted to dominate different specific situations: areas of steep slope, unstable soil, and recurrent fire.

Second, the anthropogenic rtle in altering the landscapes of the Mediterranean is not diminished by recognizing that it works through altering the relative areas suitable for dominance by the oak-dominated woodlands/forests and by the various scrub formations. Deforestation and overgrazing resulted in accelerated erosion and that increased the areas of steep and unstable slope suitable for expansion of the natural scrublands.

Third, European scholars and many others need to reframe what exactly is "natural." How far back does one have to go to get to a "pristine" nature, one not "sullied" by human activities, as a goal for landscape restoration? In the Mediterranean borderlands, agriculture and animal husbandry and their transformations of the landscape go back 10,000 to 11,000 BP. The millenia just before that comprised the colder Younger Dryas (~13,000 - 11,500 BP) and before that the warm Late Glacial Interstadial of ~15,000 - 13,000 BP. It is hopeless romanticism to hearken back to a pristine nature in the Mediterranean borderlands and possibly in California as well, given human settlement here sometime after 15,000 BP.

Fourth, agriculture and animal husbandry may well have produced the kind of mosaicking in the Mediterranean landscape that really could prevent or reduce massive conflagration by reducing the ground cover, particularly the highly flammable ground covers of maquis, garrigue, and grassland. The rural depopulation and abandonment of agropastoralism in the European Mediterranean has ironically been accompanied by an increase in landscape-consuming fires. The goats might not have been so bad, after all! This counterintuitive effect might be explicable in terms of Cohen's findings about fire behavior and ignition potential. The low cover of crop plants and fodder deny wildfire ladders into the crown through prevention of brand-formation and amplified temperatures.

Fifth, California researchers need to settle the balance between fuel accumulation, stand age, meteorologic effects, and ignition sources to understand wildfire dynamics in California chaparral, coastal sage, and grassland.

Sixth, no matter how the California "Fire Wars" work out, the message for urban planning in the Wildland-Urban Interface is clear: Discourage residential development in the W-UI and reprivatize vulnerability to the household level to encourage firewise home modification to promote structural survival in the worst California firestorms.

I wish to acknowledge the field projects in Malibu, the Santa Monica Mountains, and the Orange County South Coast Wilderness conducted during the Geoscience Diversity Enhancement Project at CSULB (NSF Grant # GEO- 0119891) for inspiring my interest in this literature.

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© Christine M. Rodrigue, Ph.D., 2004
last revised: 12/12/04