It has been said that forests came before human beings, deserts followed them. Desertification is becoming a major problem as more and more of the world's land surface is turned into desert.
Desertification is a process of soil erosion and land degradation. Deserts are typically areas covered in sand but desertification extends to mean any areas where land can no longer sustain plant and animal life.
Soil is made up of millions of active, living microrganisms and bacteria. The process of decomposition and the production of humus gives life to plants and animals which in turn provides food for other plants and animals - including humans.
When a land's soil is no longer fertile enough to allow plants to grow the land is effectively dead - it becomes dry, dusty and arid.