La course contre la montre face à l’érosion : la stratégie développée en Médoc (Gironde, France)

International audienceThe sandy coastline of Aquitaine is subject to severe erosion that is accelerating under the effect of climate change. In the Médoc, this phenomenon has led to the discovery of ancient levels of estuarine marshes containing an exceptionally well-preserved archaeological and natural heritage, long sealed under the dune mass and in an anaerobic environment that preserves the organic remains. These characteristics make this region an ideal laboratory for studying the relationships between societies and their environment. An interdisciplinary team has therefore set itself the goal of cross-referencing data on human occupations and the major phases of landscape evolution, in order to reconstruct the history of societies' adaptation to environmental changes, from the Neolithic to the end of Antiquity.Working on the foreshore nevertheless presents strong constraints. The legibility of the soil and the accessibility of the remains is uncertain, depending on the movement of the sandbanks and the baïnes. Winter is the best time to work because the beach is cleared of sand. The periods of high tides must be favored in order to have a maximum of working time. The presence of various types of remains, especially eco-facts, requires significant resources in terms of analysis and conservation. Finally, the management of the operation schedule may not be adapted to the needs.Faced with these constraints, over the years a strategy has been developed in the Médoc, both in terms of intervention and data acquisition methods and partnerships. Regular monitoring through surveys and the elaboration of an archaeological map using GIS allows us to prioritize excavations according to the degree of vulnerability of the remains. The excavation mainly concerns the wooden structures which are surveyed using photogrammetry, dismantled in several phases, and then restored in the form of 3D models. Geoarchaeological investigations and paleoenvironmental analyses are carried out at the same time as the archaeological operations.The success of the research project owes everything to the institutional and administrative framework that was gradually put in place. We first benefited from several collaborative projects within the Laboratoire d'Excellence Sciences Archéologiques de Bordeaux, which were then relayed by the Ministry of Culture, then by the Communauté de Communes Médoc-Atlantique and finally by the Région Nouvelle-Aquitaine, through the current ESTRAN project.While it is to be welcomed that research is benefiting for the moment from satisfactory conditions, it is nonetheless a question of local and temporary solutions. To ensure the conservation through study of a coastal archaeological heritage doomed to disappear, it is urgent to develop an institutional framework and permanent funding, the only ones able to respond to the scientific and heritage issues related to climate change.Le littoral sableux aquitain est soumis à une érosion sévère qui s’accélère sous l’effet du dérèglement climatique. Ce phénomène entraîne la mise au jour d’anciens niveaux de marais estuariens recelant un exceptionnel patrimoine archéologique et naturel. Une équipe interdisciplinaire s’est fixé pour objectif de croiser les données relatives aux occupations humaines et aux grandes phases d’évolution du paysage, afin de restituer l’histoire des trajectoires d’adaptation des sociétés aux changements environnementaux, du Néolithique à la fin de l’Antiquité. Travailler sur l’estran présente néanmoins des contraintes fortes en termes d’accessibilité au terrain, de temps de travail contraint par les marées, d’investissement humain et financier, et de cadre administratif. Au fil des années, une stratégie a été élaborée en Médoc, tant en ce qui concerne les méthodes d’intervention et d’acquisition des données que les partenariats. S’il convient de se féliciter que les recherches bénéficient pour l’instant de conditions satisfaisantes, il n’en reste pas moins qu’il s’agit de solutions locales et temporaires. Pour assurer la conservation par l’étude d’un patrimoine archéologique littoral voué à disparaître, il est urgent de développer un cadre institutionnel et des moyens pérennes, seuls à même de répondre aux enjeux scientifiques et patrimoniaux liés au changement climatique