A simple definition of shifting swidden cultivation would be :
an agricultural system in which patches of forest are cleared by fire and not cultivated continuously, i.e. implying periods of fallow longer than the periods during which a plot is cultivated. (see CONKLIN, 1957)
In areas where average rainfalls are high, clearing is not followed by burning though agriculture is still based on shifting cultivation. One then speaks of 'slash and mulch' : the dead leaves provide a compost in which crops are planted, an alternative to the fertilizing ashes produced by burning ;
Example : on Siberut Island in Sumatra ; in Ok and Ankave territory in Papua New Guinea, Darien (Panama, Colombia) in tropical America.
Swidden cultivation on swampland ought to be mentioned separately ; it is quite common in Asia (especially in Borneo).
The swamp forest is cleared and wet rice is planted in the field. After two or three crops, the plot is left fallow. The forest does not take as long to regenerate as on dry land.
The fundamental aspect of shifting cultivation is the absolute necessity of a fallow period : regeneration of the forest canopy is an integral part of such an agricultural system. To achieve this, the tree stumps are usually left in place while clearing, and crops are planted between them ; this prevents the soil from being packed down, airs the ground and allows water to circulate between the roots of the trees that have been felled.
There are three types of agriculture, depending on the kind of crops that are planted :
- plants that vegetatively regenerate themselves, perennial, continuous growth ; harvesting is not seasonal;
Tubers : manioc, yam, taro, sweet potato ; fruits (that need cooking) : plantain ;
- cereals or seed plants, annual ; they ripen simultaneously and must then be harvested ;
Maize, mountain rice (in dry land areas), irrigated rice (in swampland areas, rice paddies) ;
- combination of both ;
The most common combination in Africa and America is maize intercropped with tubers or bananas. In Asia, the field of mountain rice may be used for manioc after the rice harvest ; many rice growing populations have irrigated rice fields and swidden plots on which they grow tubers (e.g. in the Philippines or in Borneo).
Main staple crops :
Amazon Basin : manioc combined with maize, and plantain in some places; sweet potato and yam are common but always minor crops.
Equatorial Africa : manioc, plantain, yam, combined with maize in varying proportions.
Asia (Peninsular Malaysia and the islands of South-East Asia) : rice (mainly mountain rice) is the most important plant and rice cultivation is spreading more and more, gradually replacing tubers and bananas. In Borneo, the latter crops have already been replaced by rice, and it is gradually spreading in the Moluccas and in the Philippines. But usually, rice and tubers continue to co-exist. Sago cultivation in some places. In New Guinea, sweet potato, taro, yam and plantain in varying proportions and sago in places.
In any case, traditional agriculture is based on 'crop combination' : each plot is planted with many different sorts of plants, all intercropped (different species and different varieties).
The number of different plant species within one field can be counted by the dozen. For example : there are 50 different sorts of plants on a Kenyah swidden plot in Sarawak, at least 40 on a Ngbaka swidden in Central Africa ; the Hanunóo in the Philippines grow 413 different plants (species and cultivars) on their swiddens. The number of different cultivars for each species used by any single ethnic group is also impressive : the same Hanunóo grow 92 varieties of mountain rice ; the New Guinea Yafar grow 20 clones of taro, 30 of banana trees and 24 varieties of sugar cane, while the Wayãpi in French Guiana grow 32 clones of manioc, 11 of banana and 12 of yam.
Such diversity is the result of the history of how these populations mastered agriculture, and is also an irreplaceable gene pool.
Shifting swidden cultivation and permanent agriculture do not necessarily exclude one another, especially in South-East Asia, and one must therefore distinguish between complete and partial systems of swidden agriculture.
In areas where sedentary cultivators specialize in irrigated rice cultivation (e.g. in the Philippines or in Borneo), they often supplement rice crops with vegetables grown on swidden plots ; the forest is essential as a water regulator for irrigation and its management is therefore carefully planned. The same can be said for the upper reaches of the Amazon Basin where populations combine cultivation on the land left clear after the water has subsided and swidden agriculture on the high terraces.
Another important distinction is between the different types of vegetation cleared for the swidden plots : pioneer swiddening (clearing old primary forests that have reached their climax[2]) or cyclical swiddening (clearing secondary forests). This implies a further distinction between fallow land that has been abandoned (friche) and land that is only left fallow on a temporary basis (jachère) (rotation). This has specific implications for the forest ecosystem and its regeneration, but also for human populations : habitat and the type of mobility involved are very different, being linear in one case and cyclical in the other.
SPENCER (1966) set up a complex typology for South-East Asia, combining the parameters of both cultivated plants and mobility into four categories and 18 sections.
We have thus seen that engaging in swidden agriculture presents a whole variety of different characteristics depending on 1) which type of forest is cleared (primary forests or old fallows), 2) the movement followed when choosing a new plot for clearing (random, linear, cyclical), and 3) the type of habitat mobility associated with clearing new plots.
What is more, the amount of time any single plot will be cultivated for varies from one ethnic group to another depending on the type of plants that are grown on it.
Deciding to abandon a plot, the number of plots cultivated simultaneously and their age, and having fallow periods of different lengths, all these factors imply that there will be very different types of agricultural systems and that they will vary from area to area and from one ethnic group to another.
In shifting swidden agriculture, there are always at least three plots being worked on at the same time : one plot under full cultivation, the previous year's plot producing tubers or bananas, and the new plot that is being prepared (cleared and planted) and which will only yield the following year.
clearing with fire is largely used by new settlers or cattle breeders searching for new land and aims at occupying the land on a permanent basis.
- A so-called harmonious fallow allows for complete regeneration and the forest thus recovers its original fertility.
- On the other hand, one speaks of interrupted fallow when felling is accelerated (either because of population pressure or because the population's territory has been reduced), the cycle shortened, and plots re-used before the forest has had time to recover completely. Interrupted fallow is a sign that swidden agriculture has begun to dysfunction. Accusations made against this type of agriculture, making it responsible for deforestation are only aiming at a result ; the origin of this situation lies in misdirected political and economic pressures and the application of such policies by exogenous farmers.
- swidden agriculture is based on a combination in time and space of trees and crops ;
- swidden agriculture relies on the forest for its very existence since forest regeneration is what restores soil fertility ;
- it is a self-regenerating agricultural system..
These characteristics are what differentiate swidden agriculture from western agricultural systems which need energy supplies and fertilizers to function adequately and which operate on very different kinds of soils. Apart from being beneficial to the forest ecosystem itself, swidden agriculture is, from an economic point of view, perfectly adapted to developing countries with low population densities.
Fallow land is never really 'abandoned' :
- while it is growing back, secondary forest attracts many animals and thus provides ideal hunting grounds ;
- many wild plants grow back providing fruits and vegetables, and the old cultivated plants continue to yield (bananas, manioc, etc) ;
- it provides deadwood and construction materials ;
- people often increase its potential by planting or encouraging the growth of useful trees.
It is therefore of great practical value to study traditional techniques for looking after trees and more particularly those put into practice on fallow land. What techniques have indigenous populations developed to accelerate or encourage forest regeneration ?
There are several levels at which trees are integrated within the agricultural system :
- the simplest case is when trees considered valuable are not felled during clearing (and remain therefore after the land reverts to fallow and while the forest regenerates) ;
- organized fallow : plants that will be left to grow are selected (by selectively weeding the fallow plot) and useful species transplanted. The forest structure is modelled for human purposes (tree plantations).
More simply, the idea is to use fallow land to create an orchard , whether using food producing trees (fruit trees) or commercial products (oil-producing nuts, hevea, pepper, etc) and this is especially common in Borneo. In the central and western areas of the Amazon Basin also, Indians and mestizos organize some of the fallows into orchards combining different tree species.
The most sophisticated examples are to be found in the agroforests of Sumatra, useful forests reorganized with tree species chosen by people, planted, tended, and combined with other species from natural seedbeds (which they also partly tend).
- mixed woodland and fields : in between cultivated plots, non-cleared forest areas are left free of any agricultural impact, but are sometimes enriched with tree species useful to human beings.
In any case, it is especially important to keep some mature trees that will provide fruits and the necessary seeds for forest regeneration.
[2] Climax : a dynamic equilibrium when the forest reaches full maturity and is able to reproduce itself indefinitely under existing conditions (see WHITMORE 1975).