The Encroaching Dunes of the Portuguese Coast. A Geohistorical Perspective

Late Holocene dunes migration is intricately linked to climate change and anthropogenic actions. Along the Portuguese coast, large-scale sand drifts occurred between the sixteenth and nineteenth centuries, sometimes associated with the Little Ice Age (LIA) period, characterised by long-term cooling across the north Atlantic region. Primary historical sources, coupled with scientific data about paleoenvironmental conditions and OSL ages were used to analyse the spatial and temporal extent of the sand drift occurrences and explore their impact on coastal communities. Covering the period of the past millennium, the study describes the main drivers for drift events in Portugal. The results show the intensification of sand drift episodes after 1500 AD, which can be attributed to both natural forcing factors and human activities (e.g., agriculture and intensive deforestation). It is also clear that human pressure on dunes was dominant after 1800, when dunes fixing strategies through afforestation programmes were seen as the best solution to control sand encroachment. The negative impact of the drift-sands was an important trigger for the management of coastal areas and determinant for the implementation of a set of environmental policies in Portugal. Through a geohistorical perspective, the paper discloses the human-nature interactions over time, and the long-term efforts of governments to control natural processes, contributing to large-scale landscape transformation of the Portuguese coastal dunes.