The Mediterranean Basin represents the largest area of MTEs in the world, covering a complex landscape with a large amount of topographic and climatic heterogeneity. The total area of the region is about 2.3 x 103 km2, nearly 10 times greater in size than any other MTE region. This area includes more than20 nations arrayed on both sides of the Mediterranean Sea. While coastal areas are extensive because of the large archipelagos and islands within the Mediterranean, much of this area consists of mountainous terrain with many areas above 2000 m elevation and peaks reaching as high as 4500 m.
The geographic position of the Mediterranean Basin is also an important factor in understanding the biodiversity of this region. Lying at the juncture of three continental landmasses, it holds a geologic history
with dynamic changes associated with plate tectonics, mountain uplift, and active vulcanism. Strong
climatic shifts that took place during the Plio-Pleistocene period, most notably major glacial episodes,
resulted in a telescoping of many communities into the Mediterranean Basin and provided for opportunities
for geographic isolation and speciation. In contrast to other MTEs, the great majority of the Mediterranean Basin is underlain by limestone. Local areas of volcanic or siliceous parent material are present, however.
The climatic features of the Mediterranean Basin are often used to define this region, but the range of dominant and widespread woody species such as holm oak (Quercus ilex) and olive (Olea europea) also are used as bioindicators of the region. To the north, the mediterranean-climate region grades into more mesic regions with summer or year-round patterns of rainfall. To the south, the Mediterranean region intergrades with the winter rainfall desert of the northern Sahara. Climates of the mediterranean Basin are notable for their high interannual variation in both rainfall and temperature extremes.
The large area of the Mediterranean Basin, coupled with its topographic and climatic heterogeneity, make for complex assemblages of vegetation types. There are extensive woodlands dominated by both evergreen and deciduous species of oak and evergreen sclerophyllous shrublands of many forms. These shrublands are often differentiated into types depending on the height of the vegetation. Tall sclerophyllous shrublands that may include small evergreen trees are termed maquis. Several species of mediterranean pine may be present in this community. A middle height shrubland, generally occurring on calcareous substrates, is termed garrigue. Finally, low semiarid evergreen shrublands in the eastern Mediterranean Basin are commonly termed phrygana in Greece and batha in Israel. A long history of human impacts on the natural landscape has strongly impacted community structure and diversity.