population from rural to urban areas due to overall economic growth and the expansion of nonagricultural jobs. It should be noted, however, that because of industrialization, acid rain and other air pollutants are a serious threat to forests in some temperate areas (World Resources Institute, 1985).
On the other hand, deforestation in many developing countries is believed to be increasing. As shown in Figure 27.2, recent estimates of tropical deforestation are larger than the 1981 to 1985 projection of the U.N. Food and Agriculture Organization. As indicated in both this figure and Figure 27.1, deforestation estimates very tremendously; it is not clear whether estimation techniques have changed or the rate of deforestation has increased. Table 27.1 shows the rate of deforestation for a number of developing tropical countries (World Resources Institute, 1990).
Recently, a number of tropical forestry experts met to discuss the causes of tropical deforestation and what could be done to slow deforestation. They arrived at a number of conclusions, some of which are summarized below (Smithsonian Institution/International Hardwood Products Association, 1990):