There is no unequivocal definition of the Mediterranean Basin. More often, this area is understood in terms of its climatic pattern; namely, an area with a low annual precipitation, over two-thirds of which occurs during the mild winter months, whereas the summers are dry and often hot. Places sharing this climatic regime have distinctive semi-arid plant communities, known locally as ‘monte bajo’ in Spanish, ‘garrigue’ in French, ‘macchia’ in Italian and ‘xerovumi’ in Greek.

According to Quézel (1981), the distribution of these sclerophyllous scrub communities is mainly coastal and much more restricted geographically than the Mediterranean bioclimatic region as defined by Emberger et al. (1962). There is thus a considerable discrepancy between botanical and climatological maps, depending mainly upon geomorphology (Figure 17.1). In places where an elevated mountain range rises steeply from the sea, as in France, Italy and parts of the Balkans and Turkey, the extension of Mediterranean habitats is greatly reduced and both botanical and climatological limits more or less overlap. This is not the case, however, in North Africa, Iberia and the Middle East.

In North Africa, hereafter called Maghreb, the Mediterranean climate ends with the 150 mm isohyet, thereby including the pre-desertic mountains known as the Saharan Atlas (Emberger et al., 1962). Unlike the map of Emberger et al., Quézel's map does not expand the Mediterranean region farther south than the main Atlas range, but includes the Sous plain and the Draa valley (Atlantic Morocco), home of several tropical species of mammal, such as Mastomys, Xerus and three species of Crocidura.

In Spain and the Balkans, Mediterranean shrublands are absent from the northernmost portions of these peninsulas, although they experience a mediterranean-type climate.