A modern technique to halt desertification in the Libyan Jamahiriya

Abstract

Although the Sahelian region of northwestern Libya receives less than 300 mm of rain per year, it is suitable for raising crops with low moisture requirements because the soil moisture is augmented by heavy depositions of dew brought in by humid winds from the sea. But if this region is to remain productive and not be converted to desert, it must be protected from encroaching dunes. Trees planted to stabilize dunes cannot survive unless surface movement of sand is halted before planting. Recently the customary method of stopping sand movement by erecting low barriers has been replaced in parts of this region by spraying a thin mulch of bitumen over the sand to prevent its movement and to conserve the maximum amount of moisture in the soil. Bitumen is applied in a layer about 2–3 mm thick immediately after a good rain. Species adapted to arid climates, such as some eucalypts and acacias, are then planted over the treated area. Once established these trees not only break the force of the winds, but through deposition of leaves prevent evaporation and sand movement. Survival of trees in mulched areas has been about 20–30% greater than on comparable areas using traditional methods.