Inside a barrier around stabilized sand dunes, palm and tamarisk trees have been planted and are growing well. - - Fight Against Sand Dune Encroachment. This FAO project aims at assisting the Government of Morocco in the fight against sand dune encroachment of palm plantations in the Draa and Ziz Valleys, in the south of Morocco. The new methodology of sand dune fixation is being applied in order to assist in the rural development of areas affected by desert encroachment.