Palynology for the Mediterranean vegetation history: human-environment interactions in a changing climate

The Mediterranean basin has always featured, and still has, extremely rich environmental biodiversity. This natural richness and variety has been enriched and conditioned by the development of several cultures. A huge set of biological archives provides evidences of flora and vegetation changes in the Mediterranean regions along time. These changes have occurred not only during the distant past, but also in the recent one. Altogether they determined the shape of the present-day plant landscape. Palynology has been extensively used to reconstruct different scenarios through the geological times. Besides many expected results, some surprises were found. It is not surprising that a consistent contingent of subtropical taxa was still present in the Italian Pliocene flora (Bertini and Martinetto 2011, Palaeogeography, Palaeoclimatology, Palaeoecology, 304: 230-246; Sadori et al. 2010, Quaternary International, 225: 44–57) and that steppe and grassland formations covered in most occasions the Mediterranean lands during glacial times (Bertini 2010, Quaternary International, 225: 5-24). On the contrary, the presence of dense oak forests in central Sicily around 9000 years ago (Sadori and Narcisi 2001, The Holocene, 11: 655-671), the expansions of Abies alba woods along the central Tyrrhenian coast until mid Holocene (Bellini et al. 2009, The Holocene, 19: 1161-1172), and the persistence of pine forests in central Spain until the last millennia (Carrión et al. 2010, Review of Palaeobotany and Palynology, 162: 458–475) could be puzzling. If we consider the vegetation changes occurred in the last millennia we have to admit they are the results of interlaced environmental and cultural changes (Mercuri and Sadori 2013, chapter 30, The Mediterranean Sea: its history and present challenges. Springer, Dordrecht; Sadori et al. 2010, Plant Biosystems, 144: 940 – 951). Mediterranean habitats have been continuously transformed by climatic changes occurring at a global scale. In the meantime, the environment has been exploited and the landscape shaped by different human groups and societies (Mercuri et al. 2011, The Holocene, 21: 189-206; Kouli 2013, Vegetation History and Archaeobotany, 21: 267-278; Mercuri et al. 2013, Quaternary International 303: 22-42). Joint actions of increasing dryness, climate oscillations, and human impact are hard to disentangle, and this becomes particularly true after the mid-Holocene (Roberts et al. 2011, The Holocene, 21: 3-13; Sadori et al. 2011, The Holocene, 21: 117-129). Important changes in Mediterranean vegetation seem to have coincided either with marked increases in social complexity or with enhanced aridity during the Holocene, or with both of them