Shifting cultivation, also known as “slash-and-burn” agriculture or swidden farming, is a traditional land-use system characterized by the cyclical pattern of clearing, cultivating, and abandoning plots of land. Shifting cultivation is defined by FAO (1) as "a farming system in which relatively short periods of cultivation are followed by relatively long periods of fallow." Practiced for many years, particularly in tropical regions, it remains a vital livelihood strategy for millions. It is estimated that about 300-500 million people globally carry out this type of system (2). Farmers typically cultivate a plot of land for a relatively short period, usually ending when the soil becomes depleted, or the land is overwhelmed by weeds. Once this point is reached, the land is left fallow for a significantly more extended period to allow natural processes to restore its fertility.
Core principles of shifting cultivation - in steps
At its core, shifting cultivation is a system of resource management that seeks to balance human needs with the regenerative capacity of ecosystems.
- The shifting cultivation cycle begins by selecting the site for cultivation.
- Then, the site is cleared by cutting and subsequent burning, mulching, or their combinations, such as in slash-and-burn or slash-and-mulch methods. Burning the cleared vegetation releases nutrients into the soil, creating fertile ground often called milpa or swidden.
- Farmers then plant high-yielding crops on this prepared land. The land stays cultivated for a relatively short period, usually 2-3 years, when the crop yields decline due to soil exhaustion.
- After cultivation, the land is left idle for an extended fallow period, allowing natural vegetation to restore soil fertility and structure. This fallow period can range from 10 to 20 years or even longer. Cultivators move to new plots as soil fertility declines, repeating the cycle.
Shifting cultivation systems: key characteristics
Shifting cultivation systems are marked by high diversity and complexity, involving the simultaneous growing of ten or more crops in combination with trees (agroforestry) and livestock (mixed farming). These systems are labor-intensive, relying on minimal use of purchased off-farm inputs, with soil fertility restoration based on nutrient cycling, lengthy fallow periods, biological nitrogen fixation, and compatible species selection. Typically practiced by small landholders, these operations are managed by family labor.
Shifting cultivation's core practice is intercropping. Intercropping maximizes soil nutrient utilization while ensuring diverse food production for the farming family. This practice also helps control pests, diseases, and soil erosion, common challenges in tropical regions. Farmers can maintain a consistent food supply throughout the year by staggering crop planting. Additionally, existing trees are often preserved for their various benefits, including medicine (Neem tree, Azadirachta indica, whose leaves have been used traditionally for the treatment of inflammation, infections, fever, skin diseases, and dental disorders ), food, and shade for crops. (3)
Common crops and areas
The specific crops cultivated in shifting systems vary widely depending on regional agroecological conditions, cultural preferences, and market demands. However, some common crops include:
- Cereals: Maize (corn), rice, millet, sorghum
- Legumes: Beans, peas, soybeans
- Root crops: Cassava, yams, sweet potatoes
- Other crops: Vegetables, fruits, and cash crops like coffee or cocoa
Shifting cultivation is primarily practiced in tropical and subtropical regions with abundant rainfall, such as the Amazon Basin, Central America, and Southeast Asia. These regions experience consistently warm temperatures, with average monthly temperatures exceeding 18°C year-round. The growing season is lengthy, with daily temperatures consistently above 20°C for over 180 days. Additionally, these areas receive heavy rainfall throughout the year. While the Amazon basin enjoys relatively steady precipitation, sub-Saharan Africa experiences a distinct dry season lasting one to two months.
Benefits and challenges
Shifting cultivation offers several advantages, particularly in regions with low population density and abundant land. The fallow period allows natural processes to restore nutrients in the soil, improve soil structure, and control pests and diseases. By maintaining diverse landscapes with varying stages of vegetation, shifting cultivation can support high levels of biodiversity. It also provides a reliable food source and other resources for many rural communities, supporting subsistence livelihoods.
However, the system faces challenges, especially in areas with high population pressure or insecure land tenure. Shortened fallow periods due to population growth can lead to soil degradation, nutrient depletion, and decreased productivity. Expanding agricultural frontiers can contribute to deforestation and loss of biodiversity. Additionally, the increasing demand for cash crops can disrupt traditional practices and lead to unsustainable land use.
The future of shifting cultivation
To address these challenges and enhance the sustainability of shifting cultivation, several strategies can be implemented:
- Prolonged fallow periods: Encouraging more extended fallow periods to allow for complete soil recovery.
- Agroforestry integration: Incorporating trees and shrubs into the system improves soil fertility, provides additional products, and enhances biodiversity.
- Crop diversification: Growing various crops to reduce the risk of crop failures and maintain soil health.
- Improved land management techniques: Adopting conservation practices such as terracing and contour planting to reduce erosion.
- Secure land tenure: Providing farmers with secure land rights can incentivize sustainable management practices.
- Market integration: Supporting the development of value-added products from shifting cultivation systems can increase farmers' incomes and reduce pressure on the environment.
Shifting cultivation is a complex and dynamic system that has sustained human populations for many years. By understanding its principles and challenges, strategies can be developed to promote sustainability and resilience in changing environmental and socioeconomic conditions.
References
- https://www.fao.org/home/en
- Li, P., Feng, Z., Jiang, L., Liao, C., & Zhang, J. (2014). A review of swidden agriculture in Southeast Asia. Remote Sensing, 6(2), 1654-1683.
- Subapriya R, Nagini S. Medicinal properties of neem leaves: a review. Curr Med Chem Anticancer Agents. 2005 Mar;5(2):149-6. doi: 10.2174/1568011053174828. PMID: 15777222.