Karst Geomorphology and Environmental Change

Whilst about 12 per cent of the earth’s dry and ice-free land is covered by carbonate rocks (limestone, marble, and dolomite), the proportion is significantly higher in the landscapes that border the Mediterranean Sea. These rock types are especially widespread in the northern part of the region and limestones in particular reach great thicknesses in Spain, southern France, Italy, the Balkan Peninsula, and Turkey and in many of the Mediterranean islands. Abundant precipitation in the uplands of the Mediterranean has encouraged solutional weathering of these carbonate rocks for an extended period. The region contains some of the deepest karst aquifers in the world, with many extending deep below present sea level (e.g. Bakalowicz et al. 2008). The regional fall in base level associated with the Messinian Salinity Crisis allowed the formation of very deep, multiphase karst systems in several parts of the Mediterranean basin (e.g. Mocochain et al. 2006). Thus, karst terrains and karstic processes are very significant components of the physical geography of the Mediterranean basin. Indeed, along with the climate and the vegetation, it can be argued that limestone landscapes (including limestone bedrock coasts) are one of the defining characteristics of the Mediterranean environment. Much of the northern coastline is flanked by mountains with bare limestone hillslopes (Figure 10.2) drained by short and steep river systems whose headwaters commonly lie in well-developed karst terrain. Karst terrains are also well developed in the Levant and in the Atlas Mountains of Morocco and Algeria, while relict karst features can be identified in the low-relief desert regions of Libya and Egypt (Perritaz 2004) (Figure 10.1). Mediterranean karst environments are also associated with distinctive soils, habitats and ecosystems as described in Chapters 5, 6, and 23. The nature and evolution of the karst landscapes across the Mediterranean region displays considerable spatial variability due to contrasts in relief, bedrock composition and structure, climatic history, and other factors. The karst geomorphological system is distinguished from other systems (e.g. glacial, fluvial, coastal, and aeolian) because of the dominant role of dissolution which results in water flowing in a subterranean circulation system rather than in surface channels (Ford 2004).