The Tertiary–Quaternary Environmental History of the Mediterranean Basin: The Background to Mediterranean Island Environments

Abstract

The Mediterranean Sea was once part of a much larger ocean which encircled the Earth. This was the Tethys Ocean which existed c.200 × 106 years ago and which subsequently diminished in extent due to the convergent movement of the African and Eurasian plates. By c.65 × 106 years ago Tethys had contracted to become the Mediterranean Sea. Since then there have been episodes of drying and flooding, low and high salinity, low and high sea levels, and cold and warmth, as well as volcanic activity and earthquakes. Many of these events are linked with climatic change and/or tectonic activity. This dynamism is reflected in the ecological changes within the sea itself and in its encircling landmasses as well as its many islands. The environment of the last 65 × 106 years has thus been anything but uniform or stable. A particularly turbulent period of environmental change occurred during the last 2 × 106 years, approximating to the Quaternary period. As high latitudes experienced major advances of ice sheets and glaciers interspersed with warm interglacial stages, the Mediterranean Basin experienced substantial temperature changes on a similar cyclical basis. Forests, grasslands and shrublands, with associated fauna, underwent continual reassembly as temperatures rose and fell. As the present interglacial, the Holocene, opened c.12 ×103 years ago, temperatures ameliorated and the ecosystems which characterize the present began to assemble. However, the Holocene is unique insofar as a new agent of environmental change began to transform landscapes. The population of modern humans (Homo sapiens) was expanding from ice-age refugia (Sykes 2001) and appropriating the resources of the Mediterranean Basin first as huntergatherers and later as agriculturalists. The environment and ecosystems of this region hardly had time to reassemble their interglacial characteristics before there was an onslaught by this new, cultural driver of environmental change. This onslaught continues today as agriculture, industry, tourism, pollution, urbanization, rural depopulation and introduced plants and animals exact their tolls. All of these natural and cultural factors have affected the Mediterranean Islands to some degree.