Forests and Trees

The world's forests are retreating rapidly in response to the expansion of human activities, driven in large part by population growth. An estimated 59,500 million square miles of tropical forest, nearly equivalent in size to the state of Florida, disappeared each year during the 1980s,1 and the pace is probably similar in this decade.2 The world's tropical forests have already lost anywhere from one-fifth to one-third of their original size. 

Analysts have long argued about whether deforestation results more from landless farmers clearing trees for subsistence production or from the timber industry's logging for profit. Both activities relate to population growth, although logging for profit is also tightly linked as well to high levels of per capita wood consumption in wealthier countries. The balance of recent opinion is that farmland extension and fuelwood collection now contribute more than commercial logging to deforestation, and this proportion is probably increasing.3 Some countries, such as Thailand and the Philippines, have restricted logging as their forested area has shrunk, but it is more difficult to balance the needs of forests with those of landless farmers.

The amount of forested land in wealthier countries is also responding to changes in consumption patterns and in economic activity as well as in population size. In some areas of the eastern United States, for example, tree cover is returning to land that was once farmland but became unprofitable for agriculture decades ago. Rising demand for paper and wood products of all types nonetheless is contributing to the loss of forests in western North America and elsewhere. And air pollution‹including acid rain, ozone smog and heavy metals‹is also threatening the health of forests in North America and Europe.4 As with other environmental trends, no single cause explains deforestation. Population growth increases the scale of a host of human activities that result almost inevitably in the loss of trees. While newly planted trees can replace those that disappear, reforestation is not remotely keeping up with the retreat of forests today, nor are regrown and managed forests likely to harbor the wealth of plant and animal species that natural forest ecosystems shelter. The pressure of further population growth is likely to challenge all countries with remaining tropical forest. About 60 percent of the population growth occurring in this decade is taking place in such countries, and an even higher percentage of the world's projected population will live in them by 2025.5