A REVIEW OF HABITAT CHANGES IN THE CAMARGUE - AN ASSESSMENT OF THE EFFECTS OF THE LOSS OF BIOLOGICAL DIVERSITY ON THE WINTERING WATERFOWL COMMUNITY

For the last 50 years, drastic changes have occurred in the Camargue. The loss of c. 40,000 ha of natural areas (33,000 ha of wetlands) was related to the extension of agriculture, salt exploitation and industry. On most of the remaining wetlands (mostly private hunting estates), management involved division of the marshes into smaller dyked units and large inputs of freshwater, resulting in a decrease in mean water salinity and an increase in duration of flooding. The original unpredictable variations in water level and water salinity, a characteristic of Mediterranean seasonal marshes, has been replaced by a tendency towards predictable permanent freshwater marshes. Consequently the species composition of aquatic habitats has changed from diversified Mediterranean to monospecific continental-type communities. The higher plant biomass favours use by wintering waterfowl which are, in turn, probably limited by high hunting pressure. These changes result in losses of biological diversity at the intra- and inter-habitat, as well as at the Mediteranean and continental, levels. New concepts of conservation should be proposed which take into consideration the biodiversity of the delta as a whole, including private properties, instead of isolated management plans for reserves only.