Presentation on theme: "The Construction of Scrub in California and the Mediterranean Borderlands: Climatic and Edaphic Climax Mosaic or Anthropogenic Artifact? B41B-0113 There."— Presentation transcript:
The Construction of Scrub in California and the Mediterranean Borderlands: Climatic and Edaphic Climax Mosaic or Anthropogenic Artifact? B41B-0113 There is a marked difference in the representation of Mediterranean scrub vegetation (e.g., chaparral, maquis) in North American and European literature in biogeography and ecology. Authors discussing this vegetation in the California context accept that it is a natural response to the Mediterranean climates, with their late summer and fall fires, and steep terrain. Debate here focusses on the extent to which humans have modified or, indeed, can modify "natural" fire regimes. European authors frame this vegetation instead as a secondary successional formation in a landscape that "should" be dominated by oak woodland and forest. The widespread presence of Mediterranean scrub is cast as an artifact of human disturbance over thousands of years, mediated through overgrazing, deforestation, accelerated erosion, and anthropogenic fire. This poster will present a content analysis of the Mediterranean scrub literature, in order to engage both traditions in the construction of a unified framework for these pyrogenic formations. THE LITERATURE OF THE MEDITERRANEAN SCRUB American Geophysical Union, San Francisco, 16 December 2004 Christine M. Rodrigue, firstname.lastname@example.org, http://www.csulb.edu/~rodrigue/ 1 Department of Geography, California State University at Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840-1101 INTRODUCTION There is a marked difference in the representation of Mediterranean scrub vegetation (e.g., chaparral, maquis) in North American and European literature in biogeography and ecology. Authors discussing this vegetation in the California context accept that it is a natural response to the Mediterranean climates, with their late summer and fall fires, and steep terrain. Debate here focusses on the extent to which humans have modified or, indeed, can modify "natural" fire regimes. European authors frame this vegetation instead as a secondary successional formation in a landscape that "should" be dominated by oak woodland and forest. The widespread presence of Mediterranean scrub is cast as an artifact of human disturbance over thousands of years, mediated through overgrazing, deforestation, accelerated erosion, and anthropogenic fire. This poster will present a content analysis of the Mediterranean scrub literature, in order to engage both traditions in the construction of a unified framework for these pyrogenic formations. ABSTRACT The two literatures agree on the basic characteristics of the Mediterranean scrub. They disagree in interpreting the functions of such scrub in the seral stages of succession. There are also differences in the debates in each literature about the rôle of wildfire in Mediterranean landscapes. Smithson, Addison, and Atkinson, Fundamentals of the Physical Environment: In all Mediterranean regions much of this woodland has been replaced by agricultural land, …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. Walter, Vegetation of the Earth in Relation to Climate and the Eco-Physiological Conditions : 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. …. 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 Woodward, an American author and student of a European biogeographer, takes a European stance in her biogeography course web page: 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.... Much of the formation is considered a subclimax developed on degraded and eroded soils and maintained in part by fire and goats. Mazzoleni, Legg, and Mueltzelfeldt, “ModMED”: The maquis and garrigue vegetation has evolved over thousands of years in an environment of heavy grazing and frequent cutting and burning. LaBianca, et al., research report to National Geographic:...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. A skeptical note is expressed by Rackham, Arid Lands Newsletter: 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. Gabler, Sager, Brazier, and Wise, Essentials of Physical Geography: 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. MacDonald, Biogeography: Introduction to Space, Time, and Life: 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. …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. Minnich, "Fire mosaics in Southern California and northern Baja California“: 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. The European view of Mediterranean scrub did affect early perceptions of California chaparral until regional ecology and biogeography matured with fieldwork in the area. Hanes, "Succession after fire in the chaparral of Southern California": 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.…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). Clements' later writings (Allred and Clements 1949) he also recognized chaparral as a true climax that persisted after recurrent fires. CONCLUSION: RECONCILIATION? First, the European tradition needs to resituate Mediterranean scrub as a natural formation adapted to steep, unstable slopes and recurrent fire Second, the anthropogenic rôle works through extending areas suitable for dominance by scrub: accelerated erosion increased areas of steep, unstable slopes in which scrub species can outcompete woodland species Third, all of us need to reframe exactly what we mean by “natural” – how far back do we have to go to get to a “pristine” nature? Before agriculture/pastoralism (10-11,000 BP) to the Younger Dryas? It is hopeless romanticism to hearken back to a pristine Mediterranean given the depth of human occupation Fourth, agropastoralism may have produced the kind of moasaicking in the Mediterranean that really could prevent or reduce massive conflagrations by reducing the mass of the ground cover and the heat emissivity and brand generation it creates, as seen in Cohen’s Structure Ignition Potential Model. Fifth, no matter how the California “Fire Wars” work out, the message for land-use planning in the Wildland-Urban Interface is clear: Discourage residential development in the W-UI and encourage the re-privatization of vulnerability to the household level so that homeowners will modify their structures to make it possible for them to survive fire without social subsidy 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.