The Seine Valley is home to an exceptional natural heritage, both from the point of view of species and spaces. From the gates of Paris to the mouth, amultitude of environments have developed and interact with each other. Each is home to habitats and species with high ecological value, often rare and threatened, and sometimes unique.The islands of the Seine are part of the systems of softwaters and the environments that one encounters are noticeable for Normandy, but more broadlyfor the European Union. Some habitats constitute habitats protected under the Habitats-Faune-Flore Directive, such as mowing meadows, arborescent sausages, mudslides and megaphorbiaes. These spaces are home to many rare and threatened plant and animal species, some of which are protected.The Seine Islands, on the other hand, have many reservoirs of biodiversity (aquatic, wet and wooded), linked together by ecological corridors belonging to several sub-trames.Although this natural heritage is now recognised, it is still threatened and severely degraded.