The extended concept of littoral active zone considering soft sediment shores as social-ecological systems, and an application to Brittany (North-Western France)

This paper applies and extends the concept of Littoral Active Zone (LAZ) of sandy beaches as a relevant dimension to observe and manage this socio ecological system. The LAZ is a dynamic zone where exchanges across land and sea occur, and this concept was initially proposed on a geomorphological background only. However, to achieve full relevance and timely address management choices tied to the functioning of soft sediment shores, it became appropriate to extend its consideration to both the ecological and social templates co-existing on the same physical unit. Current paradigms around the concept of LAZ were used as a background to organize information from different disciplines and extend the concept to different soft sediment shores (mostly sandy beaches and salt marshes), towards a global, integrated relevance of the concept. As a test for this approach, we 1) structured information on the biophysical and social templates around the concept of LAZ, 2) extended it to salt marshes and 3) applied it to the case of the Breton coast for a practical test on information organization. Such an exercise highlighted key characteristics of the LAZ using a multidisciplinary approach, but also gaps to be filled when targeting research, perception, communication, sustainable use and management of the LAZ as a functional unit.