Human Ecosystems: Botam-Tai District
SHIFTING AGRICULTURE
One of the sustainable relationships that viable mankind had with their environment was shifting agriculture in the tropical rainforest ecozones. Because it has been misunderstood by modern observes who see it operating today in areas where it is impracticable because of unsustainable high population densities, shifting agriculture is often derided as an inefficient form of agriculture that damages the environment. In fact, in conditions of sustainable population densities, shifting agriculture is ecologically very efficient, primarily because farmers do not shift to areas of primary forest but return to fallow land because it is easier to clear.
The shifting agricultural landscape is a mosaic of farms (including economic trees), land in various stages of fallow (which may be used for low intensive agriculture such as growing plantains and fruit trees), secondary and primary cultured forest, and current and abandoned house sites containing fruit trees. This land use pattern is ecologically efficient because it maintains a high level of plant biodiversity and because at any given time a large area is covered by dense vegetation. Such conditions are conducive to high animal biodiversity and although some of the larger mammals such as elephants may be discouraged (much to the relief of the farmer to whom they are a pest) primate densities may increase due to expanded food supplies, and species of non-forest birds will be attracted.
All this is beneficial to the human population, because the high level of biomass and bioactivity increases supplies of non-farm products, and also accelerates land restoration in the fallow period. This restoration arises because the land is rapidly re-colonised by forest species (including micro-fauna) from the surrounding secondary and primary forest. In this way leached nutrients are brought back to the surface by deep rooting trees, to be maintained by rapidly developing humus (the basic chemical building blocks of which are carbon, brought into the system by photosynthesis).
Moreover, the very fact that the farms are mere islands in a sea of healthy vegetation checks the tendency of soil exposed and damaged by farming (i.e. because of the decline in humus content) to be eroded by rain. The worst that can happen is that soil is removed to neighbouring land where healthy vegetation holds it, and it is not lost to the ecosystem.
Thus shifting agriculture in pre-modern times can be honestly described as agroforestry.
A major feature of the arable farming landscape is the oil-palms (sometimes planted, but usually opportunist) which farmers maintain at 2 or 3 to the hectare, and palm oil and kernel production, using primitive methods, is a long standing activity.
Compound farming
Compound farming, around houses in the village and outside, benefits from household manure which is often quite deliberate: refuse being piled around yams and plantains. Soil profiles through compound gardens often show nearly a metre of black humus-rich soil above a well structured sandy-loam. Also there are many clumps of plantains in villages that stand high above the general ground level on heaps of humus-rich soil.
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