Joseph D. Cornell currently is a Postdoctoral Research Associate at Idaho State University where he is the Ecologist/Applied Mathematician for the Sanak Island Biocomplexity Project.
- The United Nations Environment Programme (UNEP)
- Imagery of slash and burn in Brazil from NASA’s Earth Observatory
- The Food and Agriculture Organization of the United Nations
- USAID Success Story: Slashing “Slash-and-Burn” Agriculture
- Science Daily Reference: Slash and burn
- From Forest to Field: How Fire is Transforming the Amazon
Also known as “shifting cultivation”, “swidden agriculture”, or simply “jhum”, slash and burn is an ancient form of agriculture practiced by between 200 and 500 million people around the world today (2006). The two key components of slash and burn agriculture are the use of fire to prepare fields for cultivation and the subsequent abandonment of those fields as productivity declines. The inevitable decline in productivity is a result of the depletion of soil nutrients and also a result of the invasion of weed and pest species. Once abandoned however, fields are allowed to return to a more natural state as native plant and tree species reclaim the field. As a result, over time soil nutrient levels can recover to predisturbance levels, although the resulting ecosystems often retain a preponderance of plant species used by humans. While recovering, abandoned fields (also known as “swiddens”), typically are used by humans as a source of fruits, nuts, fibers, medicinal plants, and game. Once ecosystem recovery is sufficiently advanced, the field may be used again for cultivation.
Characteristics of Slash and Burn
Although the food crops used varies with location, the sequence of events in slash and burn agriculture are very similar around the world. Farmers begin to prepare a field by cutting down many of the trees and woody plants in an area. Trees that provide fruits, nuts, building materials or other useful products may be spared. The downed vegetation or “slash” is allowed to dry until right before the rainiest part of the year, at which time the slash is burned converting biomass into nutrient-rich ash. Burning also temporarily eliminates most pest and weed species. Seeds and cuttings are planted directly into the ash-covered soil. Farmers may add additional slashed vegetation from offsite as mulch which further enhances soil fertility while protecting the soil from erosion. Mulch made from the cuttings of plants which contain natural insecticides such as Piper nigrum may also be used to protect crops from pest species. Fields may be weeded one or more times, but inevitably, weed and pest species take their toll on productivity. Depending upon location, fields may be cultivated for three to five years, and again, depending upon location, be allowed to recover for as little as five to over twenty years before being cut and burned again.
Slash and Burn Agriculture Today
Slash and burn agriculture is particularly important throughout the tropics where, when done properly, it can provide people with a secure source of food and income and has been shown to be sustainable over long periods of time. Many critics point out however that when done improperly, slash and burn agriculture can quickly degrade large areas of forest which do not recover. This realization has led to a great difference in opinion between advocates and critics of the proper role, if any, of slash and burn agriculture in development. This difference in opinion may be explained by an examination of how slash and burn agriculture is being used today. In those areas of the tropics which have experienced the rapid influx of settlers such as the states of Acre and Rondonia in Brazil, slash and burn agriculture has contributed to the rapid loss of forest cover. The problem here (and in most places throughout the tropics) however is not slash and burn agriculture itself, but the rapid increase in the number of people cutting and burning the forest in order to produce food for themselves and their families. In addition, new settlers ofter lack several key resources and skills needed to successfully and sustainably use slash and burn agriculture. These include (1) a lack of detailed knowledge of local soils, climate, and ecosystems, (2) a lack of agricultural knowledge and skills (3) a lack of credit and technical support, and (4) poor integration with local and regional economies. To these problems may be added the issues of secure land tenure and access to sufficiently large areas in which to practice slash and burn agriculture. All too often, settlers enter an area, clear the forest, cultivate crops for a short period of time, and then are forced to abandon their farms because they cannot produce enough food and income to support themselves. The result is that these settlers may be forced to sell their land to larger landowners, move on to another location and start over cutting and burning new forest lands.