Deforestation

From earliest times to the present, the global extent of deforestation has been about 12%. This loss included a 19% loss of closed forest in temperate and boreal latitudes, and a 5% loss of tropical and subtropical forests.

However, in recent decades the dynamics of deforestation have changed greatly. The forest cover in wealthier countries of higher latitudes has been relatively stable. In fact, regions of western Europe, the United States, and Canada have experienced an increase in their forest cover as large areas of poorer-quality agricultural land have been abandoned and then regenerated to forest. Although these temperate regions support large forest industries, post-harvest regeneration generally results in new forests, so that ecological conversions to agriculture and other non-forested ecosystems do not generally occur.

In contrast, the rate of deforestation in tropical regions of Latin America, Africa, and Asia have increased alarmingly in recent decades. This deforestation is driven by the rapid growth in size of the human population of these regions, with the attendant needs to create more agricultural land to provide additional food, and to harvest forest biomass as fuel. In addition, increasing globalization of the trading economy has caused large areas of tropical forest to be converted to agriculture to grow crops for an export market in wealthier countries, often to the detriment of local people.

In 1990, the global area of forest was 4.23 billion acres (1.71 billion ha), equivalent to 91% of the forest Deforestation in the jungle in Brazil. Photograph by Ulrike Welsch. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. area existing in 1980. This represents an annual rate of change of about -0.9% per year, which if projected into the future would result in the loss of another one-half of Earth's remaining forest in only 78 years. During this period of time deforestation (indicated as percent loss per year) has been most rapid in tropical regions, especially West Africa (2.1%), Central America and Mexico (1.8%), and Southeast Asia (1.6%). Among nations, the most rapid rates of deforestation are: Côte d'Ivoire (5.2%/year), Nepal (4.0%), Haiti (3.7%), Costa Rica (3.6%), Sri Lanka (3.5%), Malawi (3.5%), El Salvador (3.2%), Jamaica (3.0%), Nicaragua (2.7%), Nigeria (2.7%), and Ecuador (2.3%).

These are extremely rapid rates of national deforestation. A rate of forest loss of 2% per year translates into a loss of one-half of the woodland area in only 35 years, while at 3%/year the half-life is 23 years, and at 4%/year it is 18 years.

Past estimates of global deforestation have been criticized as unreliable. These surveys of forest changes, compiled by the United Nations Food and Agriculture Organization (FAO), have been considered to be problematic because of inconsistencies in the collection methodology. Problems included potentially biased information (frequently from agencies within the country itself), inconsistent definitions of land use, and data gathering techniques that changed from survey to survey. These issues are being addressed through the use of remote sensing techniques. Satellite imaging of the forests is now being used to produce consistent and verifiable information on a global scale. Scientists and policy-makers involved with the issue of deforestation rely on dependable and accurate data. This reliable information permits them to monitor changes and accurately determine the extent of the forest.