They are places with some extreme conditions with a great strength for the developing of communities of vegetation. Habitats which must stand extreme conditions like sunstrokes, droughts and high salinity with a very poor substrate (especially in nutrients) which suffers constant changes and movements due to the winds and the lightness of the sun. These characteristics require a high specialization for the species living here. They are distributed in the communities of vegetation and in stripes depending on the distance to the sea.
Dune systems like Melide and Canexol (in the south) have a great botanic importance, they are places where the sand is placed and the wind transport them (from the sea to the land) from the high part of the beach to the inland. If there are any obstacles, like vegetation or rocks, the win loses speed and lets the sand fall.
