Dryness is accelerating degradation of vulnerable shrublands in semiarid Mediterranean environments

Semiarid Mediterranean regions are highly susceptible to desertification processes. This study investigated the influence of increasing climate aridity in explaining the decline in vegetation cover in highly vulnerable gypsum semiarid shrublands of the Mediterranean region. For this purpose, we have used time series of percent cover of vegetation obtained from remote sensing imagery (Landsat satellites). We found a dominant trend toward decreased vegetation cover, mainly in summer and in areas affected by the most severe water stress conditions (low precipitation, higher evapotranspiration rates, and sun-exposed slopes). We show that past human management and current climate trends interact with local environmental conditions to determine the occurrence of vegetation degradation processes. The results suggest that degradation could be a consequence of the past overexploitation that has characterized this area (and many others in the Mediterranean region), but increased aridity, mainly related to global warming, may be triggering and/or accelerating the degradation processes. The observed pattern may be an early warning of processes potentially affecting more areas of the Mediterranean, according to the most up-to-date climate change models for the 21st century.