Brigitte Poulin, Tour du Valat (FR)
The Man and Biosphere Unesco Reserve of Camargue comprises most of the geomorphological delta of the Rhône river in southern France. Located within the Mediterranean biodiversity hotspot, it covers 193000 ha, including 145000 ha inland. The MAB reserve comprises one natural regional park, two national nature reserves (highest protection status in France), two regional nature reserve, and eleven Natura 2000 sites, yet only 15% of its area is publicly owned. The most widespread natural habitats are lagoons, brackish/freshwater marshes with emergent or aquatic vegetation, salt marshes, and halophilous scrubs and steppes. These ecosystems are intermingled with agro-systems dominated by rice, an irrigated crop. Through a complex network of irrigation and drainage channels, 730 millions of cubic meters of water are pumped from the Rhône on average each year to compensate for river embankment. This water, primarily pumped for rice farming, is also used for flooding marshes used for nature conservation, wildfowl hunting and reed harvest, as well as for irrigation of pasture meadows. Half of this water is returned to the Rhône through drainage channels, the other half being evacuated to the Vaccarès lagoon. Camargue wetlands offer a range of regulating ecosystem services such as climate regulation, flood mitigation, water purification and nutrient cycling. They also provide important provisioning and cultural services through agriculture, salt production, fishing, cattle grazing, wildfowl hunting and bird watching. Each ecosystem type has a different dependency on water management, and resilience to fluctuations in water levels and salinity. In semi-permanent and brackish environments, seasonal variations in water levels are particularly crucial for the maintenance of emerged and submerged macrophytes and their associated fauna. External factors influencing agricultural land use (e.g. CAP reform, global market evolution for rice or biofuels) or hydrological conditions (increased salinity in the Rhône estuary, reduced rainfall due to climate change) will affect these ecosystems, with potential tradeoffs among provisioning, regulating and cultural services. For instance, wetland management for wildfowl hunting has resulted in the imposition of hydrological conditions opposed to natural cycles. This affects the native Mediterranean flora and fauna adapted to seasonal brackish wetlands, and increases vulnerability to invasive plant species. Flooding of hunting marshes and pasture meadows in summer further increases mosquito abundance with deleterious effects on ecotourism. Inadequate grazing pressure can lead to proliferation of unpalatable species, but also to habitat shift when in combination with hydrological management. Over larger time scales, reduction in freshwater availability and quality due to changes in land use, water allocation, or climate is also likely to threaten the functions, biodiversity and human uses of these wetlands. Within the Ecopotential project, the main objective is hence to make the best use of remote-sensing tools to document the evolution in the state of Camargue wetlands and the services they can deliver within a context of global changes, integrating feedback processes occurring at local scale through stakeholder management.