Deforestation is the clearing the land of forest or trees. Many people do not even know that this problem exists, although it may be occurring right in their own neighborhoods. The causes of deforestation are broad. It used to be thought that the lumber industry was much to blame, when in fact the industry is very low. Most of the land was used for various other reasons such as building and agricultural expansion. The land is used for growing crops and livestock grazing. In many cases the "Slash and Burn" method is used. This is where the farmers cut down and burn forests to get to the land that is feasible for farming. Most of the tropical soils are very poor in nutrients and can only support crops for a few years. When the soil has been exhausted it is either abandoned or turned over for livestock grazing.