poster - California State University, Long Beach

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The Construction of Scrub in California and the Mediterranean Borderlands:
Climatic and Edaphic Climax Mosaic or Anthropogenic Artifact? B41B-0113
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 # GEO0119891) for inspiring my interest in this
literature.
American Geophysical Union, San Francisco, 16 December 2004
Christine M. Rodrigue, [email protected], http://www.csulb.edu/~rodrigue/
1
Department of Geography, California State University at Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840-1101
Succession in Mediterranean
Landscapes in the European Tradition
ABSTRACT
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.
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.
THE LITERATURE OF THE
MEDITERRANEAN SCRUB
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.
Chaparral in the American Tradition
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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
The regional "climax" vegetation is characterized as oakdominated forests and woodlands, which hang on as relict
stands in a few scattered areas.
Excerpts illustrating this literature follow
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.
Changing European View of the
Human Role in Mediterranean Scrub
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American literature conveys a different impression
Chaparral is described as one of the “climax”
formations that develops in Mediterranean climate
régimes 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.
Anthropogenic impacts in Mediterranean
ecosystems are not overlooked, but the premise is
that the formation itself is a natural element of the
landscape.
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.
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Large fires brought by the end of Mediterranean
agropastorlaism has led to new skepticism
Rackham: Abandoned farmland or neglected pasture
turn into forest or shrubland…. Moreover, natural
vegetation used to be interspersed with fields and
vineyards which acted as fire-breaks.
Mazzoleni, Legg, & Muetelfeldt, “ModMED”: 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 led to the rapid succession
to woodland and accumulation of biomass. This in turn
then affects the frequency and intensity of fires.
The American Debate over Chaparral
Fire Dependency Heats up
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Americans, too, are questioning their assumptions about
chaparral and fire
Chaparral has been seen as pyrogenic, not just fireadapted, for the last few decades: “The present re-gime of
large, intense conflagrations in southern California
appears to be an artifact of fire suppression” (Minnich)
Recent writings argue that weather trumps all agedependency: “I hypothesize that fires during extreme
weather conditions have been capable of burning through
all age classes of the vegetation mosaic” (Moritz)
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
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