Ready for the next shift?
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CTA. 2001. Ready for the next shift?. Spore 96. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/46346
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore96.pdf
Trees and multistorey agriculture in Africa
Is shifting cultivation (slash-and-burn) just inefficient, and destructive of the soil and local biodiversity? Or does it offer promising models? For thousands of years, shifting cultivation has fed many, and it continues to support the livelihoods of 300 million people worldwide. And that is a conservative estimate. It can be defined in numerous ways but it is best described as a practice whereby farmers clear a patch of forest or savanna, often using fire to release the nutrients for growing crops, and then alternate periods of cultivation with periods of fallow, during which the forest and soil fertility are allowed to be restored, while the farmers shift to a new patch. Besides having many names, milpa in Belize, swidden on Niue or chitemene in southern and central Africa this way of farming has many faces, which for a long time were not recognised but lumped together. The general belief has been that in cases of low population densities and abundant forests, the periods of fallow were long enough to make this method of farming sustainable. Steady population growth during the twentieth century was assumed to have increased the pressure on the forest, unacceptably shortening fallow periods. This also led to soil depletion and shrinking forests and forced farmers to move to more marginal lands. Combine this with agriculture being modernised and intensified, and needing to meet growing demands for food, and it seems not so strange that shifting cultivation was denounced as irrational and destructive. This has certainly been true in part but research in the 1990s found that it might be a pity to throw out the baby with the bathwater. Limiting their shifts The lessons were not slow in coming. The Alternatives to Slash-and-Burn Programme, coordinated by the International Centre for Research in Agroforestry (ICRAF), was established in 1992 on the basis of assumptions similar to those described above. They did not entirely hold true. Case studies around the world indicated that although more than 15 million ha of tropical moist forests disappeared each year due to slash-and-burn farming, only 17% of the shifting cultivators cleared actual primary forest and an even smaller percentage eventually brought about a permanent treeless form of land use. Increased deforestation is more likely to be the result of civil war, drought, market mechanisms and government policies than of slash-and-burn. For instance, changes from communal to private ownership of land is giving way to loggers, miners, plantation farmers and cattle ranchers, at the same time literally stopping the shifting cultivators in their tracks. This applies less to central Africa, where deforestation in the forest fringes of the Congo basin is indeed largely caused by smallholder agriculture. Yet there are other reasons for farmers to abandon shifting cultivation and to adopt a sedentary way of farming: the vicinity of markets, schools and infrastructure also encourages people to settle. Low yielding but stable No two farmers are the same, and shifting cultivation is not one uniform way of farming. The Overseas Development Institute, a UK based research body, points out that indigenous communities, who often live in remote areas, have developed their way of farming over generations and apply long fallow periods and complex farm management practices. Each decision is carefully taken on the basis of sound agronomic criteria, resulting in a low yielding but stable and sustainable food production. On the other hand there are the new settlers, often nearer to urban areas, who focus on short-term gains from cash crops, use short fallow periods until the soil is depleted, or just move on and on. In between these two extremes, there isa continuum of farming men and women who shift part of their operations once in a while but return later. In forests, which can sustain the existing population of shifting cultivators, the practice even contributes positively to the system s biodiversity. In these cases it is crucial that the mosaic of patches in different stages of fallow, forest cover and cultivation does not get too fragmented and threaten any of the natural tree species in their survival. Where the shifting cycle cannot be maintained, a conversion to sedentary agro-forestry cultivation systems can be an option too. The central issue here is to maintain soil fertility more effectively. In recent years a whole spectrum of viable alternatives to expensive chemical fertilisers has become available. For instance improved fallow techniques which enrich the natural fallow vegetation through the planting of nitrogen-fixing and multipurpose trees to improve soil productivity. Applying manure from livestock, green manuring, mulching, planting cover crops for inter-cropping and alley farming are other examples. Agroforestry systems can be good alternatives too, such as multi-storey cultivation, systems that allow natural tree species to rejuvenate alongside annual crops and economic trees. It would not harm to lend an ear to the traditional shifting cultivators themselves or, as Paul Sillitoe of the University of Durham in England argues, to combine anthropological research with soil science. His work explained how the Wola of Papua New Guinea have developed their own sustainable system while avoiding their traditionally long fallow periods. They grow non-perennial crops semi-permanently by incorporating compost from grassy fallows into soil mounds, with sweet potato as a staple crop. Where there s a will, there s a way. [caption to illustrations] In Guinea (top), people grow the restorative Pueraria to shorten the fallow period after the cycle of slashing, burning and growing rice. Mixed cropping here in Seychelles is another option Trees and multistorey agriculture in Africa H Dupriez & Ph de Leneer CTA / Terre et Vie. 1998. 280 pp. ISBN 92 9081 1781 CTA number 860. 40 credit points