About one-third of the world’s land surface is desert or semidesert. Deserts are dry areas, with high temperature, little vegetation and scanty or no rainfall. The greatest deserts are the Sahara and the Kalahari Desert in Africa. Now question arises — why have the deserts not always been the same and why are they spreading day by day? Paintings of animals like giraffes and elephants have been found in prehistoric caves in the middle of Sahara Desert. Evidences show that the early Romans grew wheat in some areas of North Africa, which is now a desert. This indicates that these areas were transformed from fertile land to desert over a period of time. Strong winds shift the sand dunes further to cover adjacent neighbouring areas, which is a common phenomenon in deserts. The action of strong winds on bare surfaces of the desert reduces loose topsoil to fine particles of sand. This sand is deposited in mounds and is called sand dunes. The strong winds shift the sand dunes, gradually, causing the expansion of the desert. Moreover, due to very hot and dry atmosphere and also in absence of any vegetation, the process gets accelerated. Other prime reasons for soil degradation and formation of desert is poor farming practices. If a piece of land is not cultivated for long and if the trees are cut down, the topsoil will become loose and will get blown away. Too much grazing by animals like cows, sheep or goats in a semi-desert area may also lead to the expansion of deserts. Boring too many wells and pumps for water lower the underground water level and this also affect the soil, resulting in the formation of new deserts. In modern arid-zone research techniques, several measures have been undertaken to control the spread of deserts. Various methods such as preventive fencing, plantation of suitable grasses or plants are some of the techniques adopted to arrest the advance of deserts. In some areas, parts of deserts have been transformed to agricultural lands for limited cultivation. This is, however, still in the experimental stage.