Sea Life

Mediterranean Biodiversity

The Mediterranean is a sea that is defined by the fact that it is almost totally surrounded by land. Hence the name Mediterranean which is derived from the Latin medi/middle and terra/earth. The Mediterranean covers the entire southern edge of the European Union. With a surface area of 2.5 million km², it is one of the largest seas bordering Europe. It contains numerous islands, which add 19000 km of coastline to the 27000km of its continental shores. The average depth of about 1500m conceals major disparities. A relatively narrow continental shelf (with the exception of certain areas such as the North of the Adriatic Sea, the Strait of Sicily and the Aegean Sea) contrasts with great depths: over 3000m in the large basins, with records of over 5000m in some trenches.

There is geological evidence that throughout the history of our planet the Mediterranean has completely dried out and been refilled about three times due to seismic activity that has opened and closed the Atlantic gateway.

The Mediterranean is a unique ecosystem. Although it covers only 0.7% of the worldwide marine surface area, it holds 9% of its biodiversity. But it is a closed sea, bordered by heavily populated and industrialised coastlines that are visited by millions of tourists, crossed by intense maritime traffic and fed by urbanised river basins that are industrialised and farmed intensively (Ebro, Rhone, Po, Arno, Tiber, Nile).

Tourism is the number one economic activity. Nearly 250 million people visited the Mediterranean countries in 2005, in other words 30% of tourists worldwide. These figures are reflected in the vast number of beach, sailing and cruise activities. The Mediterranean is the second most popular area worldwide for cruises, with 1 million cruise passengers.

The sea in the Catalan/Balearic area receives virtually all of the great water mass of the western Mediterranean. That is the water that comes from the sea’s basin itself and that which comes through, via the Strait of Gibraltar, from the Atlantic. Atmospheric circulation is responsible for wave and current generation whilst the (very slight) tides depend upon the gravitational pull of the heavenly bodies.

In the summer the surface temperature of the Mediterranean rises due to the calm meteorological conditions. As the surface becomes warmer thermoclines are formed. A state that sees a marked vertical slope in temperatures. This summer stratification of water masses prevents their mixing vertically. In the winter unstable meteorological conditions allow the water masses to mix and thus break up the stratification. From these seasonal movements and balances coupled with the fact that the Mediterranean is an enclosed sea, the temperature at the bottom never drops below 12C.

Despite its clarity, which creates the blue colour and good visibility that we divers enjoy, the Mediterranean sea has a very rich biodiversity, with a total of 10000 to 12000 recorded marine species, and new species still being discovered.

The shallow coastal zones that support seagrasses like Posidonia oceanica are particularly productive as they are the breeding habitats for many species, including those of commercial importance. Despite legislation, sadly Posidonia seagrass beds are in decline in most parts of the Mediterranean Sea.

The majority of Mediterranean waters are under the high seas regime. Territorial waters, established by coastal States over a width of 12 nautical miles (6 nautical miles for Greece) represent 16 % of the total surface area. Few states have asked for an exclusive economic zone, but some have declared new types of zones, which are not covered by the law of the sea, such as fishing zones or ecological protection zones. These specific zones cover 31% of the surface of the Mediterranean.

Each State manages fishing in its waters. The European Union manages the fishing grounds of its Member States in the framework of the Common Fisheries Policy, consulting the Mediterranean Fisheries Regional Advisory Council. Migratory stocks or stocks which regularly move from one national area to another are managed by two regional fisheries management organisations: the International Commission for the Conservation of Atlantic Tunas for tuna, swordfish and sharks, and the General Fisheries Commission for the Mediterranean for other species.

The Mediterranean is the area of competence of two marine environmental conventions:

• The Barcelona Convention or Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean and the Mediterranean Action Plan (MAP) which is linked to it.
• The Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and contiguous Atlantic Area, of which the European Union is not a member.

History of the Mediterranean

Home to the ancient cities of Egypt, Crete, Mycenae, Greece and Rome, the Mediterranean is the birthplace of European civilisation. The Mediterranean saw the expansion of the ancient maritime powers. In the end Rome controlled the entire sea (Mare Nostrum) until the destruction of its fleet by the Vandals at Cape Bon (468). In the Middle Ages, the gradual weakening of the Byzantine Empire favoured new maritime actors: the Arabs (8th century), the Berbers (9th-10th century), the Normans of Sicily (11th century) and the Italian city-states (11th-12th century). Genoa and Venice became Mediterranean thalassocracies through their control of the trade routes to the East. This domination ended in the 15th and 16th centuries, following the expansion of two rising powers: Aragon to the West and the Ottoman Empire to the East. The Battle of Lepanto (1571) put an end to Turkish expansion. But the Mediterranean lost its commercial leadership following the development of Atlantic trade.

In the 18th and 19th centuries, the Mediterranean came under the control of the United Kingdom which took over its strategic points in order to control the route to India, which was rendered entirely maritime when the Suez Canal was completed (1869). France, on the other hand, colonised the Maghreb. During the First World War, violent battles aimed at controlling the Strait of Otranto, gateway to the Austrian Adriatic, and the Dardanelles, gateway to the Ottoman Empire. The fall of the latter allowed the United Kingdom and France to take control of the eastern and southern shores. During the Second World War, the Mediterranean was the setting for decisive maritime battles, such as the landings in Sicily and Provence. In the post-war years, the Near-Eastern and North African States gained an often turbulent independence.