Deforestation is the long-term or permanent conversion of forested land to another use. Deforestation can be a natural phenomenon: floods, hurricanes, wildfires, landslides, and droughts, for example, can all cause widespread damage and destruction to a forest. However, deforestation is frequently anthropogenic. Such anthropogenic deforestation results from destructive logging; the transformation of forest to cropland, pasture, or developed areas; and overutilization of forest resources past the point where the ecosystem can recover. Road building, oil extraction, mining, and hydroelectric dam construction also involve deforestation.

Humankind has cleared forests since its earliest days to build shelter, obtain fuel, and make way for crops and livestock. Deforestation has inevitably accompanied human settlement, development, and commerce. Rates of forest loss are highest in developing nations, where trees are harvested in response to an international demand for wood products. They are also cut down to meet domestic needs for fuel, as wood and charcoal are still widely used for cooking and heating. Tropical forests are eliminated and the land reworked to provide more profitable, exportable commodities such as beef cattle, biofuel crops, sugar, palm oil, rubber, tea, and coffee.

In its 2005 Global Forest Resources Assessment, the Forestry Department of the United Nations Food and Agriculture Organization (FAO) reported a global deforestation rate of about 13 million hectares per year between 2000 and 2005. Although forest restoration efforts, afforestation (establishing forest plantations in historically unforested areas), and natural forest expansion offset part of the destruction, the net loss remained substantial: Every year during the study period, an estimated 7.3 million hectares of forest--an area roughly the size of Panama--disappeared. (This represents an improvement over the years from 1990 to 2000, when the annual net loss was 8.9 million hectares.) Forests in Africa and South America were hardest hit; North and Central America and Oceania also experienced a net loss. Europe showed a slow expansion of forested area, and China reported a net gain due to large-scale afforestation. As of 2005, the total global forested area was just under 4 billion hectares and covered about 30 percent of the planet's land area.

Living plants take in carbon dioxide (CO2) during photosynthesis and retain, or sequester, it. The carbon is returned to the atmosphere when the plant decomposes or burns. The FAO's 2005 Global Forest Resources Assessment estimates that forests worldwide store 283 billion metric tons of carbon in their biomass alone; the carbon stored in that biomass, together with that in forest deadwood, litter, and soil, is about 50 percent more than the amount of carbon in the atmosphere.

Because of the role trees and other forest plants play in the carbon cycle, deforestation is regarded as a major source of greenhouse gas (GHG) emissions. When a forest's trees are harvested or cleared, they can no longer pull carbon from the atmosphere. Furthermore, as they burn or decompose, they release their stored carbon to the atmosphere. The FAO reports that global carbon stocks retained in forest biomass dropped by 1.1 billion metric tons annually between 1990 and 2005 in response to deforestation and forest degradation.

According to Land Use, Land-Use Change, and Forestry (2000), a report by the Intergovernmental Panel on Climate Change (IPCC), an estimated net release of 121 billion metric tons of carbon resulted from the expansion of agriculture through conversion of forest and grasslands during the 140-year period between 1850 and 1990. Approximately 40 percent of that was emitted from middle- and high-latitude areas in the Northern Hemisphere, primarily before the middle of the twentieth century; the remaining 60 percent came from low-latitude tropical forests, mostly during the latter half of the twentieth century. The IPCC attributes more than 90 percent of net carbon emissions during the1980's to land-use changes (chiefly deforestation) in the tropics.

It was during the 1980's that international concern about the widespread liquidation of forests mounted. At the 1992 United Nations Conference on Environment and Development in Rio de Janeiro, Brazil, the nonbinding Statement of Forest Principles was developed and made several recommendations for responsible and sustainable forestry. Since then, most of the world's countries have adopted forestry laws and policies that integrate environmental, economic, and social considerations. Some countries, including Paraguay, Costa Rica, China, Thailand, the Philippines, and much of Europe, have implemented deforestation bans or moratoria.

Deforestation is largely driven by economic considerations: The financial advantages of harvesting or clearing a forest are clear, while the benefits the forest provides in terms of carbon storage, biodiversity, water purification, and erosion control are less evident. Tax credits, subsidies, incentive programs, and carbon trading have been proposed to encourage forest conservation and preservation. In Costa Rica, forest loss has been halted through a combination of tax incentives and a program of payment for environmental services. In 2008, the United Nations launched the Reduced Emissions from Deforestation and Forest Degradation (REDD) Program, in which developed nations will pay developing nations to slow climate change by protecting and planting forests.

References:

1)         Food and Agriculture Organization of the United Nations. State of the World's Forests, 2007. Rome: Karen N. Kahler, 2007.

2)         Gay, Kathlyn. Rainforests of the World: A Reference Handbook. 2d ed. Santa Barbara, Calif.: ABCCLIO, 2001.

3)         Williams, Michael. Deforesting the Earth: From Prehistory to Global Crisis. Chicago: University of Chicago Press, 2003.

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