Slash-and-burn agriculture
Slash-and-burn agriculture is a farming practice primarily found in tropical regions, where forest land is cleared and burned to create space for crop and livestock production. Historically, this method allowed for fallow periods during which the land could regenerate, supporting ecological balance. However, in recent decades, increased demand for commodities such as palm oil and natural rubber has led to shorter fallow periods and intensified agricultural practices, resulting in significant environmental impacts like habitat fragmentation, soil erosion, and air pollution.
The practice can contribute to severe air quality issues, as seen during the 1997 Asian fires, which caused widespread health problems for millions due to increased particulate matter and toxic gases. Environmental degradation from slash-and-burn agriculture not only threatens biodiversity but also affects water quality and the livelihoods of local communities.
To address these challenges, there is a growing interest in alternative agricultural methods that prioritize sustainability, such as agroforestry and education about the environmental consequences of slash-and-burn practices. Transitioning to these systems could help mitigate the adverse effects while respecting the cultural contexts of communities that rely on this traditional farming method.
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Slash-and-burn agriculture
DEFINITION: Practice in which forestland is cleared and burned for use in crop and livestock production
Among the negative environmental impacts of the widespread use of slash-and-burn agriculture are habitat fragmentation, air pollution, and soil erosion.
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 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 farmers and large agribusiness, especially in Asia and Latin America, resulted in increased negative impacts on the environment.
Although slash-and-burn agriculture seldom takes place in temperate regions, some agricultural burning occurs in the Pacific Northwest of the United States. As of 2023, the practice was legal, but regulated, in Washington State.
Habitat Fragmentation
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 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.
Although slash-and-burn agriculture can have a negative environmental impact through deforestation and erosion, a 2023 study by researchers at Ohio State University found that moderate, targeted slash-and burn techniques can lead to greater plant diversity.
Human Health
The impacts of slash-and-burn agriculture on human health and the 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 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, gases, and volatile 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 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 planting season often went unnoticed. Thus it is likely that millions of people in the Tropics experience environmental health problems because of slash-and-burn agriculture that are never reported.
Soil and
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 is the impact of slash-and-burn agriculture on water quality. As erosion continues, sedimentation of streams increases. This affects stream flow and freshwater for catchment-area populations. Mixed with the sediment are minerals such as 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, deposition and migration into drinking-water supplies continues to increase.
Controlling Slash-and-Burn Agriculture
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 kind of restoration has been undertaken in many of the world’s developed nations.
Bibliography
Dean, Warren. With Broadax and Firebrand: The Destruction of the Brazilian Atlantic Forest. Berkeley: University of California Press, 1997.
Grabmeier, Jeff. "Slash-and-Burn Agriculture Can Increase Forest Biodiversity." Phys.org, 28 Nov. 2023, phys.org/news/2023-11-slash-and-burn-agriculture-forest-biodiversity.html. Accessed 23 July 2024.
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.