Tropical forests are decreasing at the rate of 12 million hectares per year due to burning of fuels,commercial deforestation and the loss of top soil amounting to 28billion tones a year. Elements such as unstable rainfall added to over-cultivation on sterile land,due to the pressures of population growth,as well as pasturing and excessive consumption of trees of firewood or charcoal,are aggravating soil,reducing farmland and promoting desertification. Six million hectares of new desert are created every year.