Calvados ensures the transition between the Massif Armoricain and the Bassin Parisien. In addition to the region's wide coastline, a great diversity of natural spaces extends along the Orne and has an ecological and landscape interest. The river is the cradle of the migration of Atlantic salmons and sea trouts that come to breed there. Clearing operations restore open natural environments such as the moors of the little Norman Switzerland and limit the growth of afforestation.