Climate changes in the central Mediterranean and Italian vegetation dynamics since the Pliocene

Pollen records and pollen-based climate reconstructions from the Italian peninsula (central Mediterranean) show clear signals of vegetation change linked to variations in water availability in the Mediterranean basin over the past 5 million years. Profound vegetation changes occurred in four major steps from the Pliocene to the present. The subtropical taxa that dominate Pliocene assemblages declined and then disappeared between 3–2.8 and 1.66 Ma (at around 2.8 Ma in the North and later in the South), progressively being replaced by temperate Quercus forests at mid altitude. In the south Italy, Quercus expanded more at around 1.4–1.3 Ma and Fagus proportions increased after 0.5 Ma. Conifer forest (first mainly composed of Tsuga then by Abies and Picea) began to expand at 2.8 Ma, probably rather at high altitude, beginning at 2.8 Ma. Mediterranean-type forest, rare during the Early Pleistocene, developed and increased in diversity during the Middle Pleistocene. Open landscapes, with higher abundances of steppic taxa, became more frequent and extensive at the onset of Glacial/Interglacial (G/I) cyclicity around 2.6 Ma and gradually expanded with more and more marked glacials. Climate reconstructions done on selected pollen records from southern Italy suggest a decline in winter temperature and annual precipitation from the early Pleistocene to the Holocene. Specifically, both precipitation and winter temperature reconstructions show changes in interglacial maxima and glacial minima at around 3–2.8 Ma, 2 Ma, 1.3–1.4 Ma and 0.5 Ma. This critical review provides evidence that the North–South precipitation gradient, with drier conditions in the South, has been a consistent feature of the Italian peninsula since the beginning of the Pleistocene.