Slash-and-burn agriculture (Encyclopedia of Environmental Issues, Revised Edition)
Slash-and-burn agriculture has been practiced for many centuries among people living in tropical rain forests. Initially, this farming system involved small populations. Therefore, land could be allowed to lie fallow for many years, leading to the full regeneration of secondary forests and hence restoration of the ecosystems. During the second half of the twentieth century, however, several factors led to drastically reduced fallow periods. In some places the use of such fallow systems ended, resulting in the transformation of forests into shrub and grasslands, negative effects on agricultural productivity for small farmers, and disastrous consequences for the environment.
Among the factors responsible for reduced or nonexistent fallow periods during the 1980’s and 1990’s were increased population in the Tropics, increased demand for wood-based energy, and, perhaps most important, increased worldwide demand for tropical commodities, especially products such as palm oil and natural rubber. These factors helped industrialize slash-and-burn agriculture, which had been practiced for centuries by small farmers. Ordinarily, when small farmers engage in slash-and-burn farming, they are able to control their fires, which might be compared in size to small forest fires triggered by lightning in the northwestern or southeastern United States. However, the continued reduction in fallow periods, coupled with increased burning by subsistence...
(The entire section is 277 words.)
Habitat Fragmentation (Encyclopedia of Environmental Issues, Revised Edition)
One of the most easily recognizable results of slash-and-burn agriculture is habitat fragmentation, which leads to significant loss of the vegetation needed to maintain effective gaseous exchange in tropical regions and throughout the world. For every hectare of land lost to slash-and-burn agriculture, ten to fifteen times that amount of land is fragmented, resulting in the loss of habitat for wildlife, plant species, and innumerable macro- and microorganisms yet to be identified. This also creates problems for management and wildlife conservation efforts in parts of the world with few or no resources to feed their large populations. The recognition of the problems caused by habitat fragmentation led to intensive discussions on global warming. While slash-and-burn agriculture by itself is not completely responsible for global warming, the industrialization of the process could make it a significant component of the problem, as more and more vegetation is fragmented.
(The entire section is 146 words.)
Human Health (Encyclopedia of Environmental Issues, Revised Edition)
The impacts of slash-and-burn agriculture on human health and the environment are best exemplified by the impacts related to the 1997 Asian fires that resulted from such practices. Monsoon rains normally extinguish the fires set by farmers, but a strong El Niño weather phenomenon delayed the expected rains in 1997, and the fires burned out of control for months. Thick smoke caused severe health problems. It has been estimated that more than twenty million people in Indonesia alone were treated for asthma, bronchitis, emphysema, and eye, skin, and cardiovascular problems as a result of the fires. Similar problems have been reported for smaller agricultural fires.
Three major problems are associated with air pollution: particulate matter, pollutant gases, and volatile organic compounds. Particulate compounds of 10 microns or smaller that are inhaled become attached to the alveoli of the lungs and can result in severe illness. Research conducted by the U.S. Environmental Protection Agency (EPA) and the University of Washington found that death rates associated with respiratory illnesses increase when fine-particulate air pollution increases. Pollutant gases such as carbon monoxide, nitric oxide, nitrogen dioxide, and sulfur dioxide become respiratory irritants when they combine with vapor to form acid rain or fog. Until the Asian fires, air pollutants stemming from the small fires of slash-and-burn agriculture that occur every...
(The entire section is 244 words.)
Soil and Water Quality (Encyclopedia of Environmental Issues, Revised Edition)
The loss of vegetation that follows slash-and-burn agriculture causes an increased level of soil erosion. The soils of the humid tropics create a hard pan underneath a thick layer of organic matter. Therefore, upon the removal of vegetation cover, huge areas of land become exposed to the torrential rainfalls that occur in these regions. The result is severe soil erosion. As evidenced by the impact of Hurricane Mitch on Honduras during 1998, these exposed lands can give rise to large mudslides that can lead to significant loss of life. While slash-and-burn agriculture may not be the ultimate cause of sudden mudslides, it contributes to the problem by predisposing the land to erosion.
Associated with erosion is the impact of slash-and-burn agriculture on water quality. As erosion continues,sedimentation of streams increases. This sedimentation affects stream flow and freshwater discharge for catchment-area populations. Mixed with the sediment are minerals such as phosphorus and nitrogen-related compounds that enhance algal growth in streams and estuaries, which depletes the supply of oxygen that aquatic organisms require to survive. Although fertility is initially increased on noneroded soils, nutrient deposition and migration into drinking-water supplies continues to increase.
(The entire section is 191 words.)
Controlling Slash-and-Burn Agriculture (Encyclopedia of Environmental Issues, Revised Edition)
Given the fact that slash-and-burn agriculture has significant effects on the environment, not only in regions where it is the mainstay of the agricultural system but also in other regions of the world, environmental activists and scientists have encouraged the exploration of different approaches to agriculture in the regions using the slash-and-burn system. Because slash-and-burn agriculture has evolved to be a socioculturally accepted way of making a livelihood, to be successfully implemented any recommended changes to this practice must be consistent with the ways of life of peoples who have minimal resources for extensive agricultural systems.
Among the alternatives are new agroecosystems, such as agroforestry systems and sustainable agriculture systems, that do not rely so much on the slashing and burning of forestlands. These systems allow for the cultivation of agronomic crops and livestock within forest ecosystems, thus protecting soils from being eroded. Another approach involves the education of small rural farmers, absentee landlords, and big agribusiness concerns in developing countries so that they understand the environmental impacts of slash-and-burn agriculture. Small rural farmers do not have the resources to renovate forestlands that have been slashed and burned for farming, but the big businesses that profit from such farming can organize restoration of the original ecosystems; this...
(The entire section is 221 words.)
Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Dean, Warren. With Broadax and Firebrand: The Destruction of the Brazilian Atlantic Forest. Berkeley: University of California Press, 1997.
Mazoyer, Marcel, and Laurence Roudart. A History of World Agriculture: From the Neolithic Age to the Current Crisis. New York: Monthly Review Press, 2006.
Palm, Cheryl A., et al., eds. Slash-and-Burn Agriculture: The Search for Alternatives. New York: Columbia University Press, 2005.
Terborgh, J. Diversity and the Tropical Rain Forest. New York: Scientific American Library, 1992.
Vandermeer, John H. The Ecology of Agroecosystems. Sudbury, Mass.: Jones and Bartlett, 2011.
(The entire section is 83 words.)
Background (Encyclopedia of Global Resources)
Also referred to as swidden agriculture or shifting cultivation, slash-and-burn agriculture is perhaps the simplest method employed by farmers. In its most basic form, slash-and-burn agriculture refers to a method of clearing land for cultivation by burning off the existing wild vegetation. The ash from the burned underbrush and standing timber provides a quick infusion of nutrients into the soil. Generally no other fertilizer is applied, so the soil may be exhausted quickly, forcing farmers to move on to a new site. As the yields from crops become progressively smaller, additional farmland is cleared through burning while the depleted area is allowed to lie fallow, or unused. As long as the number of people practicing slash-and-burn agriculture in a given area remains relatively constant, any damage done to the environment tends to be both localized and temporary. As populations grow, however, larger areas must be cleared while the depleted land is allowed to rest for shorter and shorter periods of time.
(The entire section is 161 words.)
Slash-and-Burn Techniques (Encyclopedia of Global Resources)
In general terms, slash-and-burn agriculture refers to the practice of moving garden sites periodically to allow depleted soil to lie fallow and rejuvenate itself naturally. Although slash-and-burn evokes an image of forestlands being burned over, the term also refers to the practice of burning off grass or other native vegetation as a way to prepare soil for gardening or farming. Swidden agriculture has been practiced in many different regions of the world, ranging from northern Europe to the tropical rain forests of South America. Shifting cultivation was common, for example, in the Scandinavian nation of Finland until the early twentieth century. Shifting cultivation remains a key method of farming throughout much of Africa, Asia, and Latin America.
In the simplest form of slash-and-burn agriculture, a fire is set and is allowed to burn the vegetation on a tract of land. After the fire has died down, food crops are planted in the burned-over area. More typically, the farmers will cut the brush and trees growing on the garden site and pile them for burning. Large trees may be left standing to be felled later as needed for firewood, or they may be cut and burned along with the brush. After the stacked brush is burned, the ashes are raked to distribute them evenly over the garden site. Crops will be planted as quickly as possible following the burn so that weeds will not have a chance to sprout. Slash-and-burn...
(The entire section is 264 words.)
The Yanomami (Encyclopedia of Global Resources)
Anthropologists and cultural ecologists once believed that soil depletion was the primary reason farmers practicing slash-and-burn would move their fields. However, studies of the indigenous peoples of South America, such as the Yanomami in the Amazonian basin, have revealed a more complex picture. The Yanomami and other rain-forest farmers follow a regular pattern in rotating their gardens through the forest. Scientists learned that a typical village, which generally had a population of about two hundred persons, moves its fields every five or six years. Studies of both the soil and the crop yields indicated that a lack of nutrients in the soil was not the probable cause for the move. Rather, the farmers would move their gardens in response to thorny weeds springing up in the field. A lack of efficient tools for weeding, combined with the light or nonexistent clothing favored in the tropical climate, made it less work to clear a new garden site than to attack the nuisance plants invading the existing one. By the fourth or fifth year after clearing an area by burning, the new brush springing up made it impractical to continue gardening in that location. This discovery has led some agronomists to suggest that the rotation of garden sites from one location to another in tropical climates could be slowed through the relatively simple means of training indigenous peoples in the use of metal hoes and scythes.
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Environmental Debate (Encyclopedia of Global Resources)
Slash-and-burn agriculture has sparked a fierce debate within the environmental movement. Many environmentalists believe that slash-and-burn agriculture is ecologically more sound than what some analysts term “industrialized agriculture,” or farming using chemical fertilizers; they are consequently opposed to encouraging farmers in developing nations to shift to other farming methods. While it is true that slash-and-burn does not pollute in the same way that farming with chemicals does, other analysts argue that growing populations that depend strictly on swidden farming will require more and more land to be cleared for use as cropland. Swidden farming may cause the least direct pollution, but through the deforestation of critical watersheds it can lead to other serious environmental problems, such as flooding. In addition, because there are generally no nutrients added to the soil other than the ashes of the burned vegetation, yields per hectare are considerably lower than those of farmland fertilized with chemicals. Consequently, slash-and-burn requires more hectares of cleared land than does chemically fertilized farming to produce the same amount of food.
(The entire section is 171 words.)
Further Reading (Encyclopedia of Global Resources)
Chagnon, Napoleon A. Yanomamö: The Fierce People. 3d ed. New York: Holt, Rinehart and Winston, 1983.
Food and Agriculture Organization of the United Nations. Improved Production Systems as an Alternative to Shifting Cultivation. Rome: Author, 1984.
Garrity, Dennis P., and Asmeen Khan, comps. Alternatives to Slash-and-Burn: A Global Initiative. Nairobi, Kenya: International Centre for Research in Agroforestry, 1994.
Haney, Emil B. The Nature of Shifting Cultivation in Latin America. Madison, Wis.: Land Tenure Center, University of Wisconsin, 1968.
Palm, Cheryl A., et al., eds. Slash-and-Burn Agriculture: The Search for Alternatives. New York: Columbia University Press, 2005.
Peters, William J., and Leon F. Neuenschwander. Slash and Burn: Farming in the Third World Forest. Moscow: University of Idaho Press, 1988.
Stewart, Omer C. Forgotten Fires: Native Americans and the Transient Wilderness. Edited by Henry T. Lewis and M. Kat Anderson. Norman: University of Oklahoma Press, 2002.
Wojtkowski, Paul A. Introduction to Agroecology: Principles and Practices. New York: Food Products Press, 2006.
(The entire section is 151 words.)
Slash-and-Burn Agriculture (Encyclopedia of Science)
Slash-and-burn agriculture refers to the process of cutting down a forest, burning the trees, and then using the cleared land to grow crops. This agricultural approachsed mainly in tropical countriess the leading cause of tropical deforestation.
Usually, some type of slash-and-burn system is used when vast areas of tropical rain forest are converted into large-scale, industrial farms. However, slash-and-burn is more often used by individual, poor farmers who migrate to the forest frontier in search of land on which to grow food. Poor farmers operate on a smaller scale, but since there are many such people, huge areas are ultimately affected. Slash-and-burn is an often permanent conversion of the tropical rain forest into farmland, leading to severe environmental problems.
Failures of slash-and-burn agriculture
Although many species of trees and other plants grow in mature tropical rain forests, the soil of many forested sites is actually quite infertile. This poor fertility is a direct result of the climate in which tropical rain forests exist. The warm, wet tropical climate is a perfect breeding ground for bacteria and other microorganisms, which decompose or break down much of the organic matter in tropical soils. Heavy tropical rains leach (dissolve) much of the remaining organic matter or soil nutrients.
(The entire section is 437 words.)