The Mediterranean Basin is characterized by its climate, where cool wet winters alternate with long hot dry summers. In some parts of the region (coasts of Libya and Egypt) annual rainfall can be as low as 50 millimeters (mm) per year, whereas in the well-watered regions, such as the Adriatic coast of the Balkan countries, rainfall is over 1000 mm. While much scientific work has been done to characterize the nature and extent of the Mediterranean ecosystem, this publication takes a pragmatic and relatively loose definition of the Mediterranean Basin, combining a geographic focus on states (as recognized by the United Nations) with a pragmatic cut off point to the north and west in Europe and Turkey, and in the Sahara Desert to the south.
The Mediterranean-rim countries hold around 400 million people, and 135 million of them live on the Mediterranean coast. A steady historical and continuing migration towards coastal areas, and specifically in the south and east of the Mediterranean, is causing pressure on the coastal environment and, more importantly, on its biodiversity. The Blue Plan estimates that the population of the northern-rim nations will grow by around 4 million between 2000 and 2025; the population of the southern- and eastern-rim nations will grow by around 98 million over the same period. Mediterranean countries are also an international travel destination for nearly 200 million visitors per year, the majority of whom visit the coastal zone. It is therefore not surprising that species inhabiting coastal sand dune systems are especially vulnerable in consequence, although a series of conservation measures have been put in place and in some countries (e.g. in France, Portugal and Spain) around 30% of the linear coastline is under some form of protection. According to the Blue Plan, between 1985 and 1995 the area of coastal protection in the region tripled to around 1,200,000 hectares.
For many countries, water resources are a key issue, except perhaps in the more water-rich Balkans. For example, of the 12 southern and eastern Mediterranean countries, the Blue Plan estimates that eight now annually use more than 50% of their renewable water resources; two of them (the Palestinian Territories and Libya) are already using more than their renewable water resources. By the year 2025 the Blue Plan estimates that 10 of the 12 countries may be consuming more than 50% of their renewable water resources, with eight of them using more than 100%. Some 70% of Mediterranean water is used for agriculture. Many wetlands have been lost through drainage and diversion (e.g. 65% in Greece, 28% in Tunisia) with implications for amphibian and aquatic reptile populations.
Low rainfall combined with unsustainable farming practices has also led to desertification and land degradation in many areas, with for example 30% of Greece being declared “threatened” and 60% of Portugal facing a moderate risk of desertification. In semi-arid areas, many years of unsustainable farming techniques have led to erosion, salinization and land degradation. Forests have always played, and still play, an important role in the daily life of the Mediterranean peoples. Although Mediterranean forests provide low direct economic returns on wood products in comparison to the Northern European forests, they play a crucial role in maintaining key ecosystem components for securing human welfare and life in the region. Previously, exploitation of the natural landscape was long, slow and relatively sustainable. In the past decades, that balance between nature and humankind has been lost. The forests are now fragile and under threat. Agricultural intensification, fires, overgrazing, and climate change are some of the major threats to Mediterranean forests and have helped lead to forest loss and degradation in many countries in recent decades. Having said that, it is also recognized that the natural cycle of forest, fire and regeneration leads to transition habitats that can be of significant biodiversity value.
With almost 5000 islands and islets the Mediterranean comprises one of the largest groups of islands in the world. There are some 4,000 islands of less than 10km2 in area in the Mediterranean, and 162 islands that are at least 10 km2. The nine Mediterranean islands of over 1,000km2 account for 83% of the total island area. The islands are of high value to global biodiversity due to their wealth of species, relatively high levels of endemism, long history of isolation, and tolerance of many kinds of disruptions, as well as their role as a natural laboratory for evolutionary studies.