 Loss of ground cover in the Sahelian Zone had driven animals and people southward in search of food and water and had given rise to new fields of sand dunes.The advancing dunes threatened to engulf wells, villages, and roads; they had even invaded Nouakchott on their march to the sea.The government secured international help to stabilize the dune field around Nouakchott and planted 250,000 palm trees to create a barrier against the encroaching desert.