Many frontier regions have been inaccessible and have not been developed or urbanised, and have therefore largely preserved their natural characteristics and landscapes. Increased transfrontier co-operation should help preserve these natural ecosystems, which constitute both a natural and a cultural heritage. The conservation of a large number of plant and animal species depends on whether they have sufficient opportunities to move around and to migrate, in transfrontier areas, which are proper ecological corridors, as well as in "interterritorial areas", which serve as "stepping stones".