Long-term anthropogenic and ecological dynamics of a Mediterranean landscape: impacts on multiple taxa.

摘要

Mediterranean landscapes resulted from the complex and ancient interaction of ecosystems and societies. Today they represent one of the world's biodiversity hotspots. These landscapes have a fine-grained mosaic and a high resilience to disturbances. However, during the last century, human pressures have led to new landscape structures and dynamics and an overall decrease in biological diversity. Within a Mediterranean landscape from southern France, we assessed the effects of land use changes on land cover and biodiversity over the last 60 years. The major land use changes involved a substantial decrease in sheep grazing and wood cutting corresponding to the abandonment of 70% of the study area. This resulted in a reduction in land use diversity which was usually high in the Mediterranean. Although land cover in the study area changed gradually (2.2% per year), over 74% changed between 1946 and 2002. This habitat shift had a subsequent impact on species distribution. Apart from amphibians and insects, most species of birds, reptiles, orchids and rare plants that responded positively to these changes were associated with woodlands, while species that responded negatively were associated with open habitats. In the Mediterranean, most rare and endemic species are associated with open habitats and are thus threatened by land abandonment. As a result, land abandonment is contributing to a decrease in local species richness and a decrease in rare and endemic species. Since similar patterns of change have been observed over most of the north-western Mediterranean, land abandonment represents a major threat for biodiversity in the Mediterranean.