Palynology of islands: A new Holocene record of landscape evolution and sea-level change from a dynamic coast of Sardinia

This study presents a high-resolution reconstruction of environment modifications of the Tirso coastal plain, the largest in Sardinia (western Mediterranean). Pollen and non-pollen palynomorphs analyses, complemented by new sedimentological and sea-level data allowed us to reconstruct changes in the coastal landscape over the last seven millennia. We documented a long-term transformation from an early estuarine open wetland to a semi-enclosed lagoon and eventually to a deltaic backswamp system under combined sea-level fluctuations and fluvial dynamics. Between 6900 and 6000 cal BP, the floodplain region, possibly frequented by humans for hunting and stockbreeding, was dominated by meadows and open semi-arid Mediterranean vegetation, with Erica maquis as natural woodland baseline. From around 6000 cal BP, the deceleration of sea-level rise and the formation of sandy barriers triggered the establishment of a sheltered lagoon with swamps hosting Alnus woodlands. Between 6000 and 4200 cal BP, the dominant evergreen thermo-mediterranean elements represented by Quercus and Erica show stability coupled with regular fire activity. This site-specific pattern, which occurred under limited human activity, contrasts with the forest dynamics observed at other sites in Sardinia and Corsica, where evergreen Quercus expanded while Erica and fire activity declined. A high-energy alluvial depositional event around 4200 cal BP indicates delta progradation that led to the isolation of a backswamp environment rapidly covered by Amaranthaceae-dominated saltmarshes. During the Bronze Age, limited pollen evidence of local farming likely reflects geomorphological instability, which prevented the southeastern Tirso floodplain from experiencing the demographic growth documented in the surrounding sectors of western Sardinia.