Article

Global change is frequently considered a major conservation threat. The Earth's c1imate has already warmed by 0.5 °C over the past century and Global Climate Models (GCM) have suggested a generai pattern of global warming over the next century or two. Some features of this warrning include a maximum warming in high latitudes, a displacement ofthe subtropical belt, in each hemisphere, a greater temporal and spatial variability in both temperature and precipitation, with stronger and more frequent violent storms and a reduced predictability of weather patterns. Recent studies show that it is possible to detect the effects of a changing climate on ecological systems. Most of approaches are based on models but experimental also exists. In order to know the vulnerability of specie s, climatic and biological boundaries are criticai data. For instance, plants in the Mediterranean region are mainly limited by moisture, so it is expected that a increase in atmospheric CO2 has a high effect on biodiversity in those biomes. Respect to vegetation types if their main structural elements have wide tolerance limits, they may be in the least danger of breakup. Vulnerability may also be reduced by greater diversity in main structural elements of a community. Models have shown that Quercus ilex s.l. community seems to be one of the most vulnerable vegetation types under a warming scenario. However the lack of knowledge concerning boundaries, i.e. the upper temperature limits of species and communities, may be important under global warming conditions. Finally, loss of biodive ~s ity in Mediterranean scenarios along the present century will be due not only to atmospheric changes in CO2 , but also to other scenarios such us land use (habitat fragmentation) or easily establishment of invasive species, coming from warrner climates, due to the largely isolation of mediterranean floras and extensive convergent evolution they suffered.