Pollen-based landscape reconstruction and land-use history since 6000 bc along the margins of the southern tunisian desert

Abstract

In south-eastern Tunisia, the role of human societies in current desert margin degradation is assumed to have involved the modification of woodland vegetation over the past 2000 years, leading to the current sparse herbaceous vegetation. In this paper, we present key results of a study based on a new multiproxy record (14C dates, pollen and clay mineralogy) from Sebkha Boujmel, Tunisia which reconstructs climate and human/landscape interactions over the past eight millennia. These new data emphasize the central role played by a Middle- to Late Holocene climate aridity trend that shaped landscapes by driving a gradual decline of Mediterranean woodland vegetation and the establishment of present-day semi-desert landscapes. The anthropogenic impacts of Neolithic pastoral societies remained limited, however human-mediated environmental change became more pronounced during the historical period and took place in a herbaceous landscape through agricultural activities during the Carthaginian-Roman periods. An abrupt environmental change is recorded during the 20th century. This significant change was related to socio-economic modifications in the way of life of the local populations, leading to over-exploitation of limited and fragile arid land resources through intensive agriculture and pastoral activities. Overall, the Holocene landscape history of southern Tunisia highlights the fragility of desert margins to both climate change and human impacts. The latter seems relatively limited during periods of pastoral subsistence characterized by high levels of mobility. However, sedentism associated with intensive grazing and agriculture has disrupted the delicate human/landscape equilibrium. These results highlight the importance of: (i) the socio-economic organization of the population; and (ii) historical events, in the exploitation and shaping of the landscape, while a direct link between climate and human activities is not evident.