Protection and enhancement of the « Geodiversity » of Beni Ghedir Valley (Tataouine, south-east Tunisie)

During last years the IUGS (International Union for Conservation of Nature and Natural Resources) and UNESCO has suggested to start projects with the idea of integration of the protection of geodiversity with sustainable economic development (Projects Geosites, Natural Monuments, etc). A better understanding of the links between cultural identity and geodiversity can help people appreciate the relevance of geodiversity in their everyday lives. In particular these links can be used to make local communities aware of their local resources and to encourage them to participate in promoting and conserving them. The research conducted in the last two years in the area of Tataouine (south-east TUNISIE) between IGRG- University of Bologna and AAMTT- Tataouine, have helped to identify in the valley of Beni Ghedir an important witness of geologic, landscape, cultural and socio- economic values, that the local authorities are keen to preserve. The overall objective of the project for the development of this valley being the exploitation of natural and anthropic benefit of sustainable development in taking specific objective the rehabilitation and development. The Béni Ghedir valley develops in the most southern sector of the «Chain of Matmata», a prominent monoclinalic structure with elevations of about the 300-600 m, characterized by the widespread presence of geomorphologic evidences of the type of "cuestas" or other forms of modelling of slopes linked to selective erosion . Particularly the chain is heavily dissected by a dense hydro-graphic network system where water erosion has configured a very dissected landscape valleys, gullies and badlands. Late Jurassic – Early Cretaceous exposed strata mainly consist of an alternation of coastal to shallow-carbonatic marine deposits. Furthermore, a variety of fossil remains (primarily terrestrial and marine vertebrates, fishes, invertebrates, megaplants and remains of dinosaurs) support intervals dominated by terrestrial sediment supply and deposition. Such beds are fundamental to the reconstruction of ancient ecosystems as well as in the reconstruction of the complicated palaeogeographic setting of the area. From a geomorphological and landscape point of view the Beni Ghedir valley show a typical arid climate, somewhat very aggressive because rainfall is highly irregular and usually intense and causing intense erosion (annual average rainfalls range between 200 and 300 mm, but daily intensities may reach 150 mm). Similarly, the accentuated topography promote the rapid concentration of runoff water thus increasing their faculty erosive. The water management is dominated by a complex system of “jessour”, a very ancient typical hydraulic system at small scale used to bank the runoff from the mountain chain. The jessour (plural of a “jesr”) are hydraulic units made of three components: the impluvium, the terrace and the dike: 1) the impluvium is the area destined for collecting and channelling of the meteoric water; 2) the terrace, formed progressively by the decantation of the carried sediments, is the area where the agricultural activities are carried out (generally olive, fig, almond, date palm, legumes etc); 3) the dike (local called “tabia”) is a barrier intended to block the sediments and run-off. The jessour influence and control almost completely the traditional agroforestry farming of the area (trees such as date palms, olives, figs, almonds, etc). Maintenance of traditional methods can reduce the negative impacts caused by modern activities and support their positive characteristics The territorial and environmental framework is completed by the presence of a typical "Ksar of mountain", the oldest form of rural housing in the area. It is a hilltop collective granary with single or multi-level long barrel vaulted storage rooms («ghorfas») which are stacked and walled to form a fortified ksar The Ksar was conceived to protect its residents and secure subsistence from ...