Human–environment interactions in the ancient Venetian lagoon (NE Italy): Palynological evidence from Altinum (Bronze Age–Roman period)

High-resolution palynological analyses from the ancient city of Altinum (∼4300–1500 cal yr BP; 2350 BCE–450 CE) illuminate how Bronze Age to Roman communities in the Lagoon of Venice experienced and responded to rapid Holocene climate variability and environmental changes. Two sedimentary archives from the archaeological context capture a sequence of environmental instabilities, including the 4.2 and 3.7 ka events, revealing their cascading effects on lagoonal ecosystems and human settlements. The 4.2 ka event led to cooler and wetter conditions in NE Italy, lowering altitudinal tree lines and reshaping wetland habitats, while a subsequent cooling pulse at 3.7 ka BP disrupted hydrological balances and compressed saltmarsh landscapes. In the study area, these shifts coincided with changes in land use and localized cultivation signals during the transition from the Early to Middle Bronze Age and again in the Final Bronze Age. Between the Bronze and Iron Ages, Altinum's emergence as a proto-urban centre unfolded against a backdrop of renewed climatic instability, amplifying vegetation sensitivity to land-use intensification. The introduction of cultivated taxa, such as Citrus during the Iron Age and Cucumis sativus during the Roman period, attests to growing commercial networks over time. The settlement experienced a period of prosperity between the 1st–2nd centuries CE but entered a marked decline around 300 CE, likely associated with cooling episodes and socio-political turbulence. Together, these records demonstrate how Altinum's trajectory was shaped by the persistent interplay between environmental change and socio-political dynamics in a vulnerable lagoonal setting.