Human communities in a drying landscape. Holocene climate change and cultural response in the central Sahara

Dagge and Hamad (2008) report that Syria is in the midst of an environmental emergency occasioned by a drought that has affected the region since 2006. Massive crop failure with harvests down by a half has produced conditions where famine and even societal collapse might be expected. Fortunately, the Syrian government has been able to ameliorate the problem with imports of food and potable water. In the distant past disasters could not have been avoided in this way, and famine would have resulted in the disaggregation of the community or at least would have forced a drastic change in survival strategies. Episodes similar to those now affecting Syria have caused societal crises throughout prehistory and history, with climate change and human abuse of landscape and natural resources playing crucial roles (Diamond 2005). Of course, local differences need to be understood and treasured. The reaction of the physical environment (the landscape) to stress is not uniform across the globe, regardless of whether we consider climate change, the impact of grazing, or any other human activity. The present day South Mediterranean arid environments (the subtropical arid belt) offer the opportunity to investigate the human-landscape relationships for the last 10 millennia. During the Holocene, the region experienced a major change in landscape: the shift from desert to savannah and back again. The environmental effects of this cycle are comparable to the ecological change which affected the mid-latitudes at the time of the waning of the Pleistocene glaciers. For instance, in the Saharan region environmental conditions favorable for animal and plant life promoted a high human concentration since the beginning of the Holocene. Consequently, the later aridification affected a densely populated landscape. The case study analyzed in this chapter deals with the effect of drought on the landscape and human communities in the central Sahara. We report and discuss the environmental changes that occurred in SW Fezzan (Libya; Fig. 5.1), by considering three different physiographic units: the Tadrart Acacus massif and the two adjoining regions lying at the opposite sides of the mountain range, the Erg Uan Kasa, and the fluvial valley of the Wadi Tanezzuft (Fig. 5.2). Furthermore, we will analyze how in the same geographic and hydrologic ecosystems, different geomorphologic units react to climate change. In addition and subsequent to environmental modifications, the human dwellers gave rise to different and complex social dynamics and adaptive strategies.