Biodiversity and Conservation Biology of Coastal Transition Zones from Mediterranean to Desert Ecosystems: An Interconti
Comparative research on Mediterranean-type ecosystems over the past several decades has largely focused on evergreen, sclerophyllous vegetation. Little attention has been given to comparative research on ecological structure and community diversity in the
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12.1 Introduction Comparative research on Mediterranean-type ecosystems over the past several decades has largely focused on evergreen, sclerophyllous vegetation. Little attention has been given to comparative research on ecological structure and community diversity in the coast al transitions from mediterranean climate zones to winter rainfall deserts. This has been a particularly important oversight by the MEDECOS research community, since the Mediterranean desert transition zones are potentially as diverse as their related "true" Med iterranean counterparts. These ecotonal areas appear to support a large diversity of plant taxa, many of which are endemic (e.g. Raven and Axelrod 1978; Shmida 1985; Cowling and HiltonTaylor, in press). It is clear that the vege tation in each of these zones is under increasing pressure as population numbers rise, and the demand for economic security increases. Threats are diverse and include tho se associa ted with the mining industry, as well as overgrazing by small livestock (goats and sheep ), agriculture and urban development. Lack of research in these arid are as has not encouraged good land use practices and all three areas discussed here are poorly conserved. As pressure on these marginal farming area s increases, so should the efforts to improve, sustain and restore them. These efforts should be based on a scientific understanding of the dynamics of the vegetation, an understanding of the processes leading to degradation as well as those involved in the rehabilitation and restoration of vegetation. This requires both theoretical inve stigations into vegetation dynamics as well as the development of practical procedures by which to evaluate such theory. The comparison of the characteristics of different systems is one of the oldest approaches in ecology, and one which is very familiar to researchers in mediterranean-type ecosystems. Comparisons between Californian chaparral and Chilean m atorral (e.g. Mooney 1977; Miller 1981), and Ecological Stud ies, Vol. 136 Run del et al. (eds.) Landscape Degradation and Biodiversity in Mediterranea n-Type Ecosystem s © Springer-Verlag Berlin Heidelberg 1998
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Australian kwongan and South African fynbos (Mileski 1983; Cowling and Witkowski 1994) have provided a large body of support for the theory of convergence. They have also highlighted the unique features of each of these systems, thus providing a focus for research questions and variety of research opportunities. More recently, comparative studies have contributed towards an understanding of the potential effects of global change. In order to predict patterns of vegetation response to global change, it is useful to examine areas with outwardly similar climatic conditions to see where the differences lie (Cowling and Midgley 1996). These differences can provide important insights into how global change might influence species composition over evolutionary time. Finally, a comparison of the effects of landscape degradation in similar systems can provide us with
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