Controlled grazing of sheep on a fenced parcel of land some 50 km west of Gabes. This demonstration will show the extent to which vegetation is degraded by grazing. The sheep are marked to indicate their weight. - - Integrated Research and Development of the Pre-Sahara Region.. The aims of this three-year project, established jointly by the Government and UNDP with FAO as executing agency, include the perfecting and demonstrating of rational methods of agricultural development in the arid zones of Tunisia, the seeking of ways to stop the present advance of the desert from the south, the establishment of areas where flora and fauna can be protected, and the introduction of training for Tunisian scientists and technical experts. The desert is at present advancing by several thousand hectares every year throughout the arid zones of North Africa, due to the uncontrolled expansion of cereal cultivation, overgrazing, and the uprooting of woody plants for firewood. These environmental problems are seen to have been brought about by the increasing population growth. It was decided that the most efficient way of combating these problems was to set up an integrated, inter-disciplinary research and demonstration programme, located in an appropriate pilot zone.