Slash and burn agriculture, a practice also known as shifting cultivation, is one of the oldest farming methods used across the tropical regions. This traditional system involves rotating crop fields across a large territory rather than farming the same plot continuously. Determining if shifting cultivation is an intensive or extensive system requires a clear understanding of how these two fundamentally different approaches to farming are defined.
Defining Agricultural Systems
The distinction between intensive and extensive agriculture centers on the relationship between inputs, land area, and output. Intensive farming aims to maximize yield from a relatively small land area through the application of high inputs. These inputs typically include substantial capital investment, machinery, synthetic fertilizers, pesticides, and a high concentration of labor per unit of land. It is a system characterized by high productivity per hectare, making it common in regions with high population density and limited available land.
Extensive agriculture, by contrast, is characterized by low inputs of capital, labor, and technology relative to the large land area utilized. While the total output can be significant due to the vast acreage, the yield per unit of land is comparatively low. This method relies more on natural resources and is generally practiced in regions where land is abundant and population density is low. The core metric distinguishing the two is the amount of resource input required to produce a unit of output from a unit of land over time.
The Mechanics of Slash and Burn Agriculture
Slash and burn agriculture is an ecological cycle of land use that begins with the selection of a forested plot, which is then cleared by cutting down the vegetation. The felled plant material, or “slash,” is left to dry for a period. This dried biomass is then burned, which serves the primary purpose of clearing the land efficiently and providing a temporary boost of nutrients to the thin tropical soils. The resulting ash is rich in minerals like phosphorus, potassium, and calcium, creating a fertile seedbed for crops.
Cultivation on the cleared and burned plot, called a swidden, is short-lived, usually lasting only one to three years. During this brief period, crop yields are sustained by the temporary fertility provided by the ash. However, the nutrient supply quickly depletes, and the invasion of fast-growing weeds accelerates, which necessitates the abandonment of the field. The land is then left fallow, allowing the natural forest vegetation to regrow and restore soil fertility over a period that can range from five to over twenty years.
Why Slash and Burn is Extensive
Slash and burn agriculture is classified as an extensive farming system because its defining characteristic is the requirement for a large total land area to maintain the cycle. Although the small cultivated plot itself may see concentrated labor during clearing and planting, the overall input of labor and capital per hectare of the entire system is low. The total system includes not only the small area under cultivation but also the much larger surrounding area in various stages of long-term fallow. The system depends on the long fallow period to naturally regenerate the soil’s fertility, rather than relying on external inputs like synthetic fertilizers. This reliance on natural processes over a vast tract of land confirms its extensive nature.
Drivers and Implications of Shifting Cultivation
The sustainable function of shifting cultivation depends primarily on low population density. The extensive nature of the system requires a large land base to support the necessary long fallow periods. When the population remains sparse, the land has sufficient time to recover its nutrient content and biomass, ensuring the practice is ecologically balanced. Population growth, however, acts as a primary driver of change that threatens the sustainability of this system. As the number of people relying on the land increases, the fallow period is shortened, preventing the forest from fully regenerating the soil’s fertility and leading to a breakdown of the ecological cycle. The result is soil degradation, reduced yields, and an accelerated need to clear primary forest, which turns a historically sustainable system into a driver of deforestation.