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Deforestation

Deforestation

THE EXTENT OF DEFORESTATION

TROPICAL DEFORESTATION

CONTROLLING DEFORESTATION

BIBLIOGRAPHY

Deforestation can be defined as the conversion of forested areas to something that is different. Net deforestation accounts for afforestation (the establishment of forests on land that has not been recently forested), reforestation (the reestablishment of forests on land that was recently forested), and the natural expansion of forests. While the calculation of net deforestation is comparatively easy on a small scale, it is difficult on a global scale, despite modern technology such as extensive satellite surveillance. There are several reasons for this difficulty.

First, there is no universally agreed-upon definition of forest. The first Global Biodiversity Outlook (2001) defines forests as ecosystems in which trees are the predominant life forms but it also notes that a more precise definition is surprisingly elusive (p. 91). The Food and Agricultural Organization of the United Nations (FAO) has a more liberal definition, classing forests as ecosystems dominated by trees (defined as perennial woody plants taller than 5 meters at maturity), where the tree crown cover exceeds 10% and the area is larger than 0.5 hectares (a half of a hectare is about 1.2 acres) (FAO 2001, p. 365). This definition thus embraces areas that some investigators think too lightly wooded to be considered a forest.

The FAO definition of forest also includes tree plantations established for the production of timber or pulp-wood (used for paper) while excluding orchards. Critics point out that the inclusion of biodiversity-poor plantations in the definition of forests understates the loss of qualities that many people associate with the word forest. These qualities are found in woodland areas that retain a significant natural element and provide habitat for varied species, including trees of different species and ages. More controversially, the FAO includes in its definition forests that are temporarily unstocked, such as areas that have been cleared and burned. Because the duration of clearance and the certainty of restocking are unclear, inclusion of such temporarily cleared land complicates estimates of the extent and trend of current deforestation.

Other problems arise in determining the extent and trend of global deforestation. The aggregate data on which the FAO relies is supplied by its member states (as is the case with all global data used by the UN). The survey and statistical resources in many poor countries are weak, and often declining. The greatest disagreement over the extent of deforestation concerns the biodiversity-rich tropical forests. Yet such areas are disproportionately concentrated in countries where statistical resources are weak. Remote sensing methods have been increasingly used to try to compensate for these deficiencies. However, data obtained by these methods are also imperfect, for reasons such as persistent cloud cover and the problem of ground-truthing on a global basis (comparing satellite data with data observed on the ground).

THE EXTENT OF DEFORESTATION

About 8, 000 years ago, forests are estimated to have covered about 15 billion acres, almost half of the earths land surface. Since then human populations and fire have had a significant impact on these forests. This impact is roughly proportional to the increase in human population and its environmental impact. In the near future there is a risk that these effects may be multiplied by climate change.

A review by the Millennium Ecosystem Assessment the most authoritative assessment of the causes, composition, and consequences of global deforestationconcluded that the worlds global forest area has shrunk by over 40 percent in recent centuries. The area of global forest in 2000 is thought to include from 9.6 to 10.9 billion acres.

The pattern of current deforestation shows two trends. At higher latitudes the boreal and temperate forest areas have either stabilized or are now expanding in size (by about 7.4 million acres per annum, of which about 2.5 million acres are plantations). However, in tropical regions, forests continue to decline in both area and quality (by about 30 million acres per annum).

Compared to the decade 1980-1990, net deforestation slowed in the following decade, from minus 30 million acres to minus 20 million acres per year. According to the Global Biodiversity Outlook 2 (2006), this trend in reduction in forest clearance has continued since 2000, with a loss of about 18 million acres per year in the five years to 2005. This decrease is mostly the result of expansion in plantations (including almost 5 million acres per annum in tropical regions). Thus, despite this slowing, the rate of loss of natural (primary) forests in the last two decades is thought to have remained about the same. Many forests are also declining in quality. Forest fragmentation, most commonly by the incursion of roads and agricultural settlements, leaves forests vulnerable to further disturbance, including drying, fires, and the invasion of exotic species.

TROPICAL DEFORESTATION

Tropical rainforest is the most extensive forest type in the world, constituting 26 percent of global forest area. Almost 60 percent of existing tropical forests are rain forest; the remainder are mostly sparse forests in dryland areas and degraded forests. In tropical forests, biodiversity, including of trees, is very high, with often more than 100 tree species per hectare. Tropical forests (both moist and dry) harbor from 50 percent to 90 percent of the earths terrestrial species.

Most tropical forests are mainly in South America (1.4 billion acres), Africa (670 million acres), and Asia (490 million acres). From 1980 to 1990 about 25 million acres of tropical forest was cleared, of which about 15 million acres were of moist forests. In the following decade, total tropical forest clearance is thought to have increased to about 37 million acres per annum (about 1.2 percent of the global tropical forest total). While some of this loss is compensated for by tropical forest plantations, plantations are much lower in biodiversity.

CONTROLLING DEFORESTATION

Deforestation has largely occurred because of the expansion of agricultural land. Increasing populations and increasing demand for products that can be grown on land that is currently forested land (such as palm oil, a source of biofuel) will drive ongoing tropical deforestation. Climate change may worsen this, though it may also allow the expansion of some high-latitude forests, even if warmer winters allow increased populations of insect pests.

While there is considerable discussion of sustainable forest management, this is not yet having a significant mitigative effect. Until population growth substantially abates, the loss of quantity and especially of quality of forests in the tropics is likely to continue. And, because of climate change, tropical deforestation could continue even after population peaks.

SEE ALSO Agricultural Industry; Boserup, Ester; Fertility, Human; Human Ecology; Population Growth; Resource Economics; Resources

BIBLIOGRAPHY

Achard, Frédéric, Hugh D. Eva, Hans-Jürgen Stibig, et al. 2002. Determination of Deforestation Rates of the Worlds Humid Tropical Forests. Science 297 (August 9): 999-1002.

Cox, Peter M, Richard A Betts, Chris D. Jones, et al. 2000. Acceleration of Global Warming Due to Carbon-Cycle Feedbacks in a Coupled Climate Model. Nature 408 (November 9): 184-187.

Food and Agricultural Organization of the United Nations. 2001. Global Forest Resources Assessment 2000Main Report. FAO Foresty Paper 140. http://www.fao.org/forestry/site/fra2000report/en/.

Hoare, A. 2005. Irrational Numbers: Why the FAOs Forest Assessments Are Misleading. London: Rainforest Foundation. http://www.rainforestfoundationuk.org/files/RF_Irrational%20numbers.pdf.

Secretariat of the Convention on Biological Diversity. 2001. Global Biodiversity Outlook. Montreal, Canada.

Secretariat of the Convention on Biological Diversity. 2006. Global Biodiversity Outlook 2. Montreal, Canada. http://www.cbd.int/doc/gbo2/cbd-gbo2.pdf.

Shvidenko, Anatoly, Charles Victor Barber, Reidar Persson, et al. 2005. Forest and Woodland Systems. In Ecosystems and Human Well-Being: Current State and Trends, Vol 1, eds. Rashid Hassan, Robert Scholes, and Neville Ash, 585-621. Washington, DC: Island Press.

Colin Butler

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deforestation

deforestation The extensive cutting down of forests for the purpose of extracting timber or fuel wood or to clear the land for mining or agriculture. Forests are often situated in upland areas and are important in trapping rainwater. Deforestation in these areas, particularly in India and Bangladesh, has resulted in the flooding of low-lying plains; it has also led to an increase in soil erosion and hence desert formation (see desertification), resulting in crop loss and economic problems for local communities. The felling and burning of trees releases large amounts of carbon dioxide, thereby increasing global carbon dioxide levels and contributing to the greenhouse effect. Rainforests, particularly those of South America, are rich in both fauna and flora; their removal leads to an overall decrease in biodiversity and the loss of plant species that have potentially beneficial pharmaceutical effects. Despite movements to reduce deforestation, economic pressures ensure that the process still continues.

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Deforestation

Deforestation

Deforestation occurs when the trees in a forested area are cut or destroyed faster than they can replace themselves. When too many trees are cut or destroyed, a very important element is taken from nature, making it difficult for the forest ecosystem to maintain a healthy balance in its natural cycle. The imbalance of the natural forest cycle threatens the humans, plants, and animals that depend on the forest for food, shelter, and protection. The loss of trees also causes negative effects on the natural cycles that affect water, soil, atmosphere, and weather.

Why Does Deforestation Occur?

Deforestation can be a natural or manmade process. Natural deforestation is caused by changes in weather patterns during glacial periods, fires started by lightning, windstorms, floods, and volcanic eruptions. Forests often recover from natural deforestation.

Deforestation caused by humans often results in permanent deforestation. Even when humans were living as small bands of hunters and gatherers they were deforesting areas for hunting animals or to practice swidden agriculture , planting areas they had cleared and moving on after the soil was spent. Over time, population levels grew and areas of permanent agriculture were established, around which civilizations began to grow. These civilizations began intensely farming fields to meet the growing demand for food. As civilizations expanded, more land had to be cleared for fields and forests had to be cut to meet the demand for wood products. The stress on forested areas grew as pressure was exerted from both swidden and permanent agriculture. These stresses intensified in times of conflict as people were forced to use more marginal areas or to overcut forests to meet their needs.

The Industrial Revolution and the technology that came with it has allowed the world population to grow at an exponential rate and has helped bring about a different lifestyle, one based on consumerism and sustained economic growth. The end result is that the last remaining areas that still have extensive forest cover, especially tropical forests, are being cut to satisfy unsustainable human consumption patterns and economic growth models. At the turn of the twenty-first century, more than one-half of the forests that once covered the globe were gone, with much of the cutting occurring over the last decades of the twentieth century.

Effects of Deforestation

The effects of deforestation can be both local and global. In the local forest ecosystem, trees, water, soil, plants, and animals are all dependent on one another to keep healthy. When trees are cut this natural balance is upset and the important functions that trees perform such as holding the soil in place, protecting groundwater, and providing food and shelter for plants and animals cannot take place. Overcutting forests and the disruption of the forest ecosystem are causing erosion of soil, the drop in water tables , loss of biodiversity as plant and animal species become extinct, loss of soil fertility, and the silting up of many water bodies. When the process continues for a long period of time or over a large area there can be total environmental collapse. Parts of the world that are now desert, such as Syria, Iraq, and Lebanon, were once covered with healthy forests.

Globally the effects of deforestation are more difficult to see. Forests play an important part in the greater natural cycles that make and affect the weather and that clean the air in our atmosphere. They keep the hydrological cycle healthy by putting water back into the atmosphere through transpiration , making clouds and rain. They also capture carbon dioxide produced by the burning of fossil fuels from the atmosphere, replacing it with oxygen and thus reducing the risk of global warming. If too many forests are cut these important functions cannot be carried out. The result could be less rain, higher temperatures, and more severe weather patterns in many regions of the world.

Local and global effects of deforestation are beginning to have devastating consequences. Some areas in West Africa, for example, are already feeling the effects of lost precipitation , higher temperatures, and increased desertification . Other areas, like Venezuela, have experienced devastating floods due to treeless slopes being unable to catch the rain from heavy storms, sending it rushing into valleys. All of these problems impact the environment, but they also take a heavy toll on humans.

Alternative Strategies to Deforestation

There are several things that can be done to decrease deforestation and to offset its negative effects. Many communities are trying to reduce the burden placed on forests by instituting recycling programs and by using alternative materials like plastics in place of wood. In business, companies have begun to use wood products that come only from certified renewable forests that are carefully managed to ensure that they are cut in a sustainable way. Alternative methods of agriculture, such as agroforestry and permaculture , promote the use of trees and the diversification of crops to reduce the stress placed on forests by large-scale agriculture. Protecting forests by creating parks and reserves is another strategy to keep forest resources intact. For those areas that are already devastated, great efforts are being made to replant once-forested lands with native species.

Other efforts are aimed at changing our ideas about the value of forests. Economists are now trying to calculate the true value of the forest as an ecosystem and the benefits it gives as a whole, not only the value of cut logs. This reevaluation will help us make more informed choices about how we use forest land. All of these efforts have helped reduce the burden on the forests, but cutting continues unsustainably. Without the cooperation of all humans to create alternative strategies to deforestation, it will continue with terrible results for the health of our planet.

see also Biome; Coniferous Forests; Deciduous Forests; Desertification; Ecosystem; Forestry; Human Impacts; Rain Forests.

Thomas Minney

Bibliography

Bryant, D., D. Nielsen, and L. Tangley. The Last Frontier Forests: Ecosystems and Economics on the Edge. Washington, DC: World Resources Institute, 1997.

Eisenberg, E. The Ecology of Eden. New York: Vintage Books, 1998.

Global Forest Watch. Forests of the World. [Online] Available at http://www.globalforestwatch.org.

Hodge, I. Environmental Economics: Individual Incentives and Public Choices. London: MacMillan Press Ltd., 1995.

New Forests Project. [Online] Available at http://www.newforestsproject.com.

Ponting, C. A Green History of the World: The Environment and the Collapse of the Great Civilizations. New York: Penguin Books, 1991.

Timberlake, L. Only One Earth. New York: Sterling Publishing Company, Inc., 1987.

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deforestation

deforestation (disafforestation)
1. The permanent clear-felling of an area of forest or woodland. On steep slopes this can lead to severe soil erosion, especially where heavy seasonal rains or the melting of snow at higher levels cause sudden heavy flows of water. In the humid tropics it may also lead to a release of carbon dioxide from the soil (owing partly to the loss of gases as soil structure deteriorates and partly to the decomposition of organic material, including tree roots).

2. A legal process whereby an area of forest land ceases to be regarded as forest under the terms of forest law.

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deforestation

deforestation(disafforestation)
1. The permanent clear-felling of an area of forest or woodland. On steep slopes this can lead to severe soil erosion, especially where heavy seasonal rains or the melting of snow at higher levels cause sudden heavy flows of water. In the humid tropics it may also lead to a release of carbon dioxide from the soil (due partly to the loss of gases as soil structure deteriorates and partly to the decomposition of organic material, including tree roots).

2. A legal process whereby an area of forest land ceases to be regarded as forest under the terms of forest law.

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deforestation

deforestation Clearing away of forests and their ecosystems, usually on a large scale, by humans. It may be done to create open areas for farming or building, or for timber. There is an immediate danger that the vital topsoil will be eroded by wind (such as the dust bowl, USA) or, in hilly areas, by rain. Proposals to clear whole regions of the Amazonian rainforests, which play a key role in maintaining the oxygen balance of the Earth, could cause an environmental catastrophe.

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