The Mediterranean, which surface area represents only 0.7% of the planet's surface sea water, is distinguished by its relatively large specific diversity; this is particularly true for marine plant species. Indeed, over one thousand macroscopic marine plant species have been observed in the Mediterranean.

Endemism is one of the main features of marine fauna and flora in the Mediterranean, as  20% of recorded species of algae are endemic.

The role of these species in maintaining the balance of marine ecosystems is primordial. The direct and indirect consequences of their decline are many, at the ecological and even the economic level (primary production, spawning grounds, nurseries, stability of coasts...).

The filling-in of sea or lagoon areas, the enlargement of beaches as well as various works undertaken on the coast (harbors, marinas...) cause harms to the meadows which, sometimes, are irreversible. In the marine areas affected by pollution there is often either the total disappearance of plant populations, or the excessive proliferation of only one or some species; what follows is an erosion of biological diversity.

Thus the Action Plan for the conservation of marine vegetation in the Mediterranean Sea is part of a series of Action Plans adopted by the Mediterranean countries within the MAP framework, devoted to the conservation of species or groups of species.