On the installation of the Mediterranean climate

In the western Mediterranean the reconstruction of the Holocene climate must take into account the heterogeneity of vegetation, the specificity of summer drought and the respective roles of climate, soils and historical hazards in the plant distribution. Moreover the anthropisation of nature, which was initiated in the mid-Holocene and ended in various ways during historical times, was characterised by the extension of sclerophyllous oaks to the detriment of deciduous oaks. A reverse development has taken place over the last 50 years in parts of the Mediterranean region where human impact (cultivation, grazing and forest exploitation) has markedly decreased. All these data show that the variations of the sclerophyllous/decidous pollen ratio throughout the Holocene sequences (Jalut et al., 1997) are only the complex result of both a dominant artefact, namely the anthropisation, and the natural evolution of the postglacial climate, this evolution being established only from indicators independent of these artefacts. ((C) Academie des sciences / Elsevier, Paris.).