Holocene environmental history of a small Mediterranean island in response to sea-level changes, climate and human impact

The aim of this study is to investigate human-climate-environment interactions in a small Mediterranean island. Comparison between palynological and palaeoentomological data from the Greco pond (Cavallo Island, southern Corsica) reveals that the island was first covered by a more-or-less open Erica arborea pasture-woodland from ca. 7000 to 6100 cal. yr B.P. Grazing animals from 7000 to 6200 cal. yr B.P., followed by a spreading of Ficus carica (marked by the bark beetle Hypoborus ficus) from ca. 6100 to 5750 cal. yr B.P., suggest that human activities could be implicated in the E. arborea forest opening. From ca. 5500 cal. yr B.P., a regional expansion of Q. ilex was recorded, but an open landscape with thermophilous and drought-tolerant plants locally took place from ca. 4700 cal. yr B.P. onward. Pastoral and agricultural biomarkers (pollen, NPP and insect) together with archaeological evidence indicate that human activities were involved in the installation of a lasting open vegetation. Simultaneously, the effects of the Holocene relative sea-level rise on the coastal wetland are recorded: (1) freshwater conditions prevailed in the Greco pond since 7000 cal. yr B.P. at least, (2) the first evidence of salt marsh development dates back to ca. 4500 cal. yr B.P., (3) a strong increase of salinity with marine intrusions were recorded at ca. 3700 cal. yr B.P. while a decline in aquatic insect diversity occurred and (4) a phase of sand dune formation was recorded from ca. 2000 cal. yr B.P. onward. Our results suggest that if large-scale climatic trend such as the Holocene relative sea-level rise could affect coastal ecosystem, effects of human activities could play the leading role in vegetation and terrestrial beetle assemblage changes in a small island context.