The Mediterranean sea and the (tropicalizzazione) The Mediterranean sea Mare Nostrum reached its present conformation between five and six millions of years ago It is a residual of the old sea called tetide which started to close with the start of the movement of collision between the African and Eurasian crostali plates

It is connected at the west to the Atlantic ocean through the straits of Gibraltar at the east it reaches the Marmara sea and the Black sea and the Suez canal. At south east it is connected to the Red sea. It is the biggest European sea and it washes twenty two countries

The Mediterranean sea is relatively poor of nutritive substances both due to its particular geomorphological climatological and hydrological characteristics and because the deep counter stream coming out from Gibraltar towards the Atlantic takes out the waters richest of nourishment, creating like this a continuous loss of organic matter

The fishes… In spite of this the Mare Nostrum is one of the temperate seas richest of varieties of fish and wild life with more than five hundred and forty species of fish Altogether it gives hospitality to eight thousand and five hundred species of macroscopic sea organisms

All this mainly due to the presence of different habitats, which favour the onset of very different ecological niches.

Unfortunately at the moment the mare nostrum doesn’t enjoy good health, and the long series of data analysed from 1900 until today confirm a progressive increase of its temperature and salinity. This process has accelerated especially from 1990, clearly in coincidence with the increasing phase of general climatic heating. (STAZIONI DI RILEVAMENTO in SPAGNA e LIVELLI DI SALINITA’ DAL 1999)

These changes have brought to the appearance and settling in the Mediterranean of foreign organisms, which generally live in warmer seas. It is a tropicalisation, which can modify the biodiversity and the delicate balance in the ecosystems.

The grassland of oceanic posidonia, already damaged by bottom trawling, now are threatened by a tropical alga too, the Caulerpa, which produces toxic substances that make it inedible by other organisms. Besides producing high amounts of oxygen, the posidonia contributes to the consolidation of the sea bottom and beaches protecting them from the erosion, and it sets up an ideal environment for the feeding and growth of fish, shellfish and other forms of life. POSIDONIA OCEANICACAULERPA TAXIFOLIA

Other damage is been provoked by new species: the triggerfish, for example, which is eaten bycorals and molluscs in the original countries, has recently attacked and destroyed the mussels in Apulia, while the pufferfish and parrot fish, which eat invertebrates, have caused a strong decrease of the species that populate our seas. TRIGGERFISH PARROTFISH

But the global heating has negative effects in other forms too. For example, the high temperatures are causing the death of impressive quantities of corals and madrepores, which can’t survive this thermal change.

The migrations don’t concern again only exotics species: there exists in fact a phenomenon by which some species of the southern Mediterranean are coming north. The bluefish, for example, is now found at more northern latitudes. As a predatory species, it can upset the usual food chain of the northern Mediterranean.

The Mediterranean is at risk for the climatiechanges due to urbanization and pollution… and consequently the biodiversity of the “mare nostrum” is in danger too. The European commission has recently proposed the “Horizon’s plan 2020”, an environmental strategy for the protection of Mediterranean sea. The central points are: To reduce the levels of pollution in the region; To promote the sustainable use of the sea and of the coasts zones; To encourage the coastal countries to cooperate on environmental themes; To help the partner countries to develop effectives politics to protect the environment; To involve the civil society into environmental decisions that concern them.

The Mediterranean is precious; it is up to our sense and at our rationality to stop its decline and safeguard its biodiversity in the future.