The biodiversity of Mediterranean-climate ecosystems is of particular interest and concern, not only because all five of these regions (the Mediterranean basin, California, central Chile, Cape Province of South Africa, western and southern parts of Australia) are among the thirty-four hotspots of species diversity in the world (Mittermeier et al. 2004), but they are also hotspots of human population density and growth (Cincotta and Engelman 2000). This relationship is not surprising because there is often a correlation between the biodiversity of natural systems and the abundance of people (Araùjo 2003; Médail and Diadema 2006) and this, inevitably, raises conservation problems. Within the larger hotspot of the Mediterranean basin as a whole, ten regional hotspots have been identified. They cover about 22 per cent of the basin’s total area and harbour about 44 per cent of Mediterranean endemic plant species (Médail and Quézel 1997, 1999), as well as a large number of rare and endemic animals (Blondel and Aronson 1999). A key feature of these Mediterranean hotspots as a whole is their extraordinarily high topographic diversity with many mountainous and insular areas. Not surprisingly this results in high endemism rates and they contain more than 10 per cent of the total plant richness (see the recent synthesis of Thompson 2005). However, of all the mediterranean-type regions in the world, the Mediterranean basin harbours the lowest percentage (c.5%) of natural vegetation considered to be in ‘pristine condition’ (Médail and Myers 2004; Chapter 7). With an average of as many as 111 people per km2, one may expect a significant decline in biological diversity in the Mediterranean basin—a region that has been managed, modified, and, in places, heavily degraded by humans for millennia (Thirgood 1981; Braudel 1986; McNeill 1992; Blondel and Aronson 1999; Chapter 9). There are two contrasting theories that consider the relationships between humans and ecosystems in the Mediterranean (Blondel 2006, 2008). The first one is the ‘Ruined Landscape or Lost Eden’ theory, first advocated by painters, poets, and historians in the sixteenth and seventeenth centuries, and later by a large number of ecologists.
Climatic Uncertainty in the Mediterranean Basin and Its Possible Relevance to Important Economic Sectors
