Vegetational markers of climatic and hydrological impact vs. human resilience in coastal subsiding plains: present pattern and historical trajectories for a future management

This PhD thesis reconstructs past environmental changes in the Sibari Plain (Calabria, southern Italy) over the last ca. 9750 years, examining the interplay between climate change and human activity as main forces on vegetation changes. This coastal plain, as a delta plain sub-environment, is characterized by a highly dynamic braided channel system. The degree of drainage from the surrounding slopes, as well as local base level changes, further influences the development and morphology of alluvial channels within the delta plain. These processes contribute to the complex mosaic of landforms typical of deltaic systems. Furthermore, subsidence affects the plain, primarily attributed to the progressive compaction of fine-grained, water-rich sediments. The water stagnation frequently favoured the spread of malaria, as attested during the Medieval period. The research investigates Holocene vegetation dynamics and the complex interplay between the environment and climate using paleopalynology. Indeed, as a transitional environment, the alluvial plain has been sensitive to water variations recorded in the sedimentary record and in the pollen record, during the last millennia. Pollen is widely recognized as a reliable proxy for reconstructing past environments and identifying anthropogenic impacts, through the analysis of high-resolution palynological sequences, integrated with multidisciplinary studies. Palynological data revealed high forest cover during the Holocene climate optimum, punctuated by climate oscillations toward wetter and drier conditions throughout the Middle and Late Holocene. Landscape opening becomes pronounced from 3100 cal yr BP, as modern Mediterranean climate established. While human presence in Calabria is documented from the Neolithic onwards, the Sibari Plain's evolution is primarily driven by climate. Human impact is mainly associated with pasture and deforestation, with limited evidence of agriculture. Wetter and drier phases, reflected in sedimentary records and associated floodplain or swampy environments, highlight the dominant climatic influence. Paleo-fluvial channels (sandy and gravelly deposits) indicate several flood events, obscuring the major Holocene dry events at 8.2 and 4.2 ka in the palynological record.