RESEARCH FINDINGS/ RELATED STUDIES
What is Slash-and-Burn?
Slash-and-burn is an agricultural technique which involves cutting and burning of forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. It is typically part of shifting cultivation agriculture, and of transhumance livestock herding. (Tony Waters, 2007) Slash and burn agriculture is the process of cutting down the vegetation in a particular plot of land, setting fire to the remaining foliage, and using the ashes to provide nutrients to the soil for use of planting food crops. (Colin Stief, 2008)
Older English terms for slash-and-burn include assarting, swidden, and fire-fallow cultivation. Today the term slash-and-burn is mainly associated with tropical rain forests. Slash-and-burn techniques are used by between 200 and 500 million people worldwide. (Slash and burn, Encyclopedia of Earth)
Slash-and-Burn Process
Generally, the following steps are taken in slash and burn agriculture: 1. Prepare the field by cutting down vegetation; plants that provide food or timber may be left standing. 2. The downed vegetation is allowed to dry until just before the rainiest part of the year to ensure an effective burn. 3. The plot of land is burned to remove vegetation, drive away pests, and provide a burst of nutrients for planting. 4. Planting is done directly in the ashes left after the burn. Cultivation (the preparation of land for planting crops) on the plot is done for a few years, until the fertility of the formerly burned land is reduced. The plot is left alone for longer than it was cultivated, sometimes up to 10 or more years, to allow wild vegetation to grow on the plot of land. When vegetation has grown again, the slash and burn process may by repeated. (Colin Stief, 2008)
History of Slash-and-Burn
In 2004 it was estimated that, in Brazil alone, 500,000 small farmers were each clearing an average of one hectare of forest per year. The technique is not sustainable beyond a certain population density because, without the trees, the soil quality soon becomes too poor to support crops. The farmers have to move on to a virgin forest and repeat the process. (Martin Skegg, 2011)
In heavily forested areas, or those with little usable soil for farming, natives often turn to slash-and-burn deforestation to feed their families. (Bambi Turner, 2011) People in many parts of the world have relied on slash-and-burn farming for thousands of years, and some estimates suggest it’s used on half of all land in tropical areas (Virginia Tech). Although this practice can serve as a successful method of agriculture in the short term, it also leads to significant problems on both local and global scales. Some scientists believe that even the mighty Mayan empire succumbed to the effects of slash-and-burn farming. For years, the Mayans relied on this technique to survive in the tropical region now known as Guatemala. Scientists have determined that just before the Mayan empire fell — around A.D. 900 — widespread deforestation had resulted in a complete absence of tree pollen. The lack of trees in the area led to a temperature increase of roughly 6 degrees, which eventually brought about widespread drought. The drought signaled the end for the Mayans (NASA).
Geography of Slash-and-Burn Agriculture
Places where open land for farming is not readily available because of dense vegetation are the places where slash and burn agriculture is practiced most often. These regions include central Africa, northern South America, and Southeast Asia, and typically within grasslands and rainforests.
Slash and burn is a method of agriculture primarily used by tribal communities for subsistence farming (farming to survive). Humans have practiced this method for about 12,000 years, ever since the transition known as the Neolithic Revolution, the time when humans stopped hunting and gathering and started to stay put and grow crops. Today, between 200 and 500 million people, or up to 7% of the world’s population, uses slash and burn
agriculture.
When used properly, slash and burn agriculture provides communities with a source of food and income. Slash and burn allows for people to farm in places where it usually is not possible because of dense vegetation, soil infertility, low soil nutrient content, uncontrollable pests, or other reasons. (Colin Stief, 2008)
Negative Aspects of Slash-and-Burn
Deforestation: When practiced by large populations, or when fields are not given sufficient time for vegetation to grow back, there is a temporary or permanent loss of forest cover. (Colin Stief, 2008) Erosion: When fields are slashed, burned, and cultivated next to each other in rapid succession, roots and temporary water storages are lost and unable to prevent nutrients from leaving the area permanently. (Colin Stief, 2008) Nutrient Loss: For the same reasons, fields may gradually lose the fertility they once had. The result may be desertification, a situation in which land is infertile and unable to support growth of any kind. (Colin Stief, 2008) Biodiversity Loss: When plots of land area cleared, the various plants and animals that lived there are swept away. If a particular area is the only one that holds a particular species, slashing and burning could result in extinction for that species. Because slash and burn agriculture is often practiced in tropical regions where biodiversity is extremely high, endangerment and extinction may be magnified. (Colin Stief, 2008) Carbon Dioxide Accumulation: Each acre of land subject to slash-and-burn deforestation releases 180 metric tons of carbon into the atmosphere (MIT). This carbon eventually reaches the Earth’s ozone layer, where it contributes to the greenhouse effect and global warming. After this initial carbon release, slash-and-burn deforestation then packs a secondary punch to the planet, as these burned trees are no longer available to convert carbon into oxygen through photosynthesis. (Bambi Turner, 2011) Pollution: Forest fires and the resulting smoke also contribute to air and water pollution, and can often rage out of control, threatening the lives of people and animals. (Bambi Turner, 2011)
The negative aspects above are interconnected, and when one happens,
typically another happens also. These issues may come about because of irresponsible practices of slash and burn agriculture by a large amount of people. Knowledge of the ecosystem of the area and agricultural skills could prove very helpful in the safe, sustainable use of slash and burn agriculture. (Colin Stief, 2008)
Solutions
A strict implementation of Revised Forestry Code (P.D. 705) is needed to halt the use of slash-and-burn in the Philippines.
Methods such as Inga alley farming have been proposed as an alternative to this ecological destruction. (Daniel Elkan, 2004)
Inga alley cropping refers to planting agricultural crops between rows of Inga trees. It has been promoted by Mike Hands. (David Adam, 2006) Using the Inga tree for alley cropping has been proposed as an alternative to the ecological destruction of slash and burn cultivation. The technique has been found to increase yields. It is sustainable agriculture as it allows the same plot to be cultivated over and over again thus eliminating the need for burning of the rainforests to get fertile plots. (Daniel Elkan, 2004)
Inga trees are native to many parts of Central and South America. Inga grows well on the acid soils of the tropical rainforest and former rainforest. They are leguminous and fix nitrogen into a form usable by plants. (rainforestsaver.org: What is Inga alley cropping?) Mycorrhiza growing within the roots (arbuscular mycorrhiza) was found to take up spare phosphorus, allowing it to be recycled into the soil. (Bunny Guinness, 2004) Others benefits of Inga include the fact that it is fast growing with thick leaves which, when left on the ground after pruning, form a thick cover that protects both soil and roots from the sun and heavy rain. It branches out to form a thick canopy so as to cut off light from the weeds below and withstands careful pruning year after year. (rainforestsaver.org: What is Inga alley cropping?)
As the crops grow, so does the Inga. When the crops are harvested the Inga is allowed to grow back. Once more it closes the canopy, is pruned, and the cycle is repeated, time and again. Leaves pruned from the tree decompose on the ground releasing phosphorus for crops. Fungi take up phosphorus to repeat the cycle.
ANALYSIS AND DISCUSSION
Slash-and-Burn system has been used by our natives way back in early civilizations. Cultivation of crops must be done in clear fields, so natives have to clear out forests and turn them into agricultural lands. Slash-and-burn method, compared to logging, proved to be an easy solution to clear out trees, since it only requires burning them instead of cutting them down individually.
Natives relied on the seemingly easy and fast system of slash-and-burn deforestation to cultivate crops and feed their families. This could solve the problem of food, but for how long? The system is not sustainable. Though it may be the easy solution at first, its positive outcome only lasts temporarily. In the long run, it is not as good a solution as it seemed.
Slash-and-burn method, when done multiple times by a lot of communities in different parts of the world, could bring about massive deforestation. Consequently, when habitats are destroyed, there would be loss of biodiversity. Soil degradation is also a negative result of slash-and-burn. Erosion could happen as well, since the trees that keep the soil strong and intact are destroyed.
Slash-and-burn system also poses threat to air quality. The smoke brought about by the combustion of trees could cause air pollution. Trees, which are naturally rich in carbon, emit a large amount of carbon dioxide when burned. The accumulation of carbon dioxide contributes to greenhouse effect and global warming.
With all the negative effects it inflicts, slash-and-burn system could be
labeled a non-sustainable method of land cultivation. Revised Forestry Code (P.D. No. 705), the law that prohibits the use of slash-and-burn method, must be strictly implemented. Also, use of alternative methods such as Inga Alley farming are encouraged to prevent further ecological destruction and to restore the environment. REFERENCES
Tony Waters, The Persistence of Subsistence Agriculture, p. 3. Lexington Books (2007)
Slash and burn, Encyclopedia of Earth
Martin Skegg, True Stories: Up In Smoke, The Guardian, 24 September 2011.
Daniel Elkan, Slash-and-burn farming has become a major threat to the world’s rainforest, The Guardian, 21 April 2004
David Adam, Earthshakers: the top 100 green campaigners of all time, The Guardian, 28 November 2006
Elkan, Daniel. Slash-and-burn farming has become a major threat to the world’s rainforest, The Guardian, 21 April 2004
rainforestsaver.org: What is Inga alley cropping?
Accessed on Sep 29, 2013
“Slash and Burn Can Contribute to Environmental Problems” By Colin Stief, 2008
Accessed on Sep 29, 2013
http://geography.about.com/od/urbaneconomicgeography/a/slashburn.htm
“What is Slash-and-Burn?”
Bambi Turner, 2011
http://curiosity.discovery.com/user/bambi-turner/answers
