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close this bookReversing the Spiral - The Population, Agriculture, and Environment Nexus in Sub-Saharan Africa (WB, 1994, 320 p.)
close this folder4. The Nexus of population growth, agricultural stagnation, and environmental degradation
View the documentThe main linkages
View the documentTraditional crop cultivation and livestock husbandry methods
View the documentLand and tree tenure systems and the Nexus
View the documentDeforestation, fuelwood, and the Nexus
View the documentLogging
View the documentNotes
View the documentAppendix to chapter 4

Traditional crop cultivation and livestock husbandry methods

For centuries, shifting cultivation and transhumant pastoralism have been, under the prevailing agroecological conditions and factor endow ments, appropriate systems for people throughout most of Sub-Saharan Africa to derive their livelihood, in a sustainable manner, from the natural resource endowment of their environment The ecological and economic systems were in equilibrium. The key to maintaining this equilibrium was mobility. People shifted to a different location when soil fertility declined or forage was depleted, allowing the fertility of the land to be reconstituted through the natural processes of vegetative growth and decay. For field cropping in forest- and bush-fallow systems, this typically involved cultivation periods of two to four years, land then being left fallow for as long as fifteen to twenty-five years. Transhumant herders' mobility generally involved a far greater geographic range, but a far shorter temporal cycle They would move the herds on extended migratory patterns as dictated by the seasonal availability of water and forage and in most cases repeat the same cycle in one or sometimes two years.

These mobile systems of shifting and long-fallow cultivation and pastoral transhumance were suitable because of low population density, abundant land, limited capital and technology, and often difficult agroclimatic conditions. As long as population growth was slow and land was available, the additional people could be accommodated by gradually taking more land into the farming cycle and establishing new settlement; on previously uncropped land. Adjustments, including gradual intensification of farming, were made as and when they became necessary, but the pace of adjustment required was slow because population growth was slow. Intercropping in Rwanda, for example, was an indigenous adaptation of this type, necessitated because shifting cultivation became increasingly constrained by rising population density.

In the absence of sufficiently rapid and widespread technological change, population growth has led to the expansion of the area under cultivation This has involved mainly the conversion of large areas of forests, wetlands, river valley bottoms, and grassland savanna to crop land. Since 1965, the area farmed in SSA has increased by over 21 million hectares (Table A-17). Much of this has taken place on ecologically fragile and agriculturally marginal land, which is not suitable for sustained farming and eventually abandoned in an advanced state of degradation. Forested land has declined by about 65 million hectares since 1965 (Table A-17) But land available to expand cultivation has become increasingly scarce in most of Sub-Saharan Africa, drastically narrowing the scope for further expansion. Most farming systems in SSA are, in fact, not land surplus systems, but landextensive systems (Eicher 1984a:455). Over the past twenty-five years, crop acreage has expanded by only 0.7 percent annually, and the population pressure on cropped land has increased sharply. On average, per capita arable land in Sub-Saharan Africa declined from 0.5 hectares per person in 1965 to 0.4 ha/person in 1980 and to less than 0.3 ha/person in 1990. For comparison, between 1965 and 1990 crop acreage declined from 0.6 ha/person to 0.4 ha/person in China and from 03 ha/person to 0.2 ha/person in India (Table A-18).

Box 4-3 Land Requirements for Chitemene Cultivation in Zambia

The suitability of land for chitemene cultivation in Zambia depends, among other things, on the density of woody vegetation available for cutting and on the land's regeneration capability. At the present levels of fram technology and productivity, a person completely dependent on chitemene requires for survival one hectare under cultivation each year (Stolen 1983:31-32; Vedeld 1983:98-100) If 50 percent of the land in an area is suitable for chitemene and the regeneration cycle is twenty-five years, the aggregate land requirement for long-term ecological sustainability of the system is 50 ha per person. In a village of 200 people, requiring a total area of 100 km, to sustain chitemene farming, individual fields would be as far as 5.1 km from the village—assuming the village land forms a perfect circle and the village is located in its center.

This simple arithmetic also shows that traditional farming and land use practices, combined with constraints on the time people can afford to spend walking to and from their fields each day, limits the size of farm settlements. Some people eventually migrate to establish new villages in virgin forest land once the situation in their home village becomes too difficult.

Because of agroclimatic and soil characteristics, the potential productive land endowment per capita in most of Sub-Saharan Africa is even poorer than these simple acreage statistics suggest. Niger, for example, is more densely populated than India or Bangladesh if account is taken of the extremely poor quality of its agricultural resource endowment Nigeria and Senegal are more densely populated than the Philippines. And Mali, Burkina Faso, and The Gambia are twice as densely sealed as Indonesia (Binswanger and Pingali 1987; Matlon 1990).


Figure 4-1 Population Pressure on Cropland in Sub-Saharan Africa, 1961-1987 (total and rural population per hectare of cropland)

There is considerable diversity among countries, but everywhere fallow periods are shortening as populations increase and the land frontier recedes. In many areas, from Mauritania to Lesotho, fallow periods are not sufficiently long anymore to restore soil fertility. Increasingly farmers are compelled to remain on the same parcel of land—yet they change their farming methods only very slowly.

These people face a critical dilemma: a central element of their traditional farming system—the ability to shift around on the land—is teeing eliminated by population pressure, yet they continue to use the other elements of their customary production systems. Where fallow periods are too short, or nonexistent, and where traditional cultivation techniques continue to be used, soil fertility deteriorates and soils are not conserved. Wind and water erosion, soil nutrient depletion, acidity, and deteriorating soil structure become common and increasingly severe. As a result, crop yields decline, forcing farmers to expand production along the already receding land frontier. This expansion occurs first within the vicinity of their settlements—on more steeply sloping land and in nearby forest, wetland and range areas. As this option becomes increasingly limited, people migrate to establish new farms, often in semiarid areas and in tropical forests where soil and climatic conditions are poorly suited to the cultivation of annual crops and yields are therefore low. The migrants bring with them the techniques they practiced in the areas they abandoned, and these techniques are often detrimental to their new environment. Although they soon begin to experiment with simple modifications in farming techniques, this indigenous adjustment has almost everywhere been too slow to keep pace with population growth in the past two to three decades.

Good pasture land is diminishing as the most productive tracts are converted to cultivation. The mobility of pastoralists' herds is further reduced as settlers increasingly cultivate bottomlands previously avaiIable to herders during their dry season migration. The concentration of increasing numbers of livestock on smaller areas destroys pasture vegetation, further reducing their carrying capacity and contributing to range degradation and eventual desertification (Gorse and Steeds 198;7; Falloux and Mukendi 1988; Nelson 1988).

Diminishing forest and woodland resources provide less fuelwood and other fores/products, many of which are of considerable importance for rural livelihood and survival systems. Similarly, surface and groundwater resources are increasingly affected by the drastic alterations in land uses and vegetative cover The effects of the worsening fuelwood and water scarcity are most directly felt by some of the most vulnerable: women and children. More time and effort are required to obtain these vital commodities. Or people must manage with less of them. One consequence of reduced woodfuel supplies is the increasing use of dung and crop by-products as fuels. This reduces their availability as farming system inputs to maintain soil fertility. Similar effects result from diminished availability of, and access to, water for household and home garden use: health and sanitation standards deteriorate, and home garden productivity declines.

These problems are gravest in parts of the Sahel and of mountainous East Africa and in the dry belt stretching from the coast of Angola through southern Mozambique. There are other countries where land appears to be more abundant in relation to their current populations These countries lie in Central Africa, humid West Africa, and southern Africa. However, much of the potentially arable land in Central and humid West Africa is under tropical forest To preserve biodiversity, maintain rainfall, and preserve the humid climate on which its tropical agriculture is based, much of this area should not be cultivated. Instead, the humid forests need to be preserved. This land has not been cultivated so far because it is poorly suited to cultivation (except possibly of certain tree crops). Soils in Africa's rain forest zones are typically low in nutrients and of high acidity. Yet even in these snore land-abundant countries, the problem that is the focus of this study can already be observed. An expanding population depending on agriculture and livestock is moving into the tropical forest areas, extending crop production and grazing into areas that are agroecologically unsuited to these forms of land use.

No analysis is available that quantifies the impact of environmental degradation caused by more people practicing traditional shifting cultivation and transhumant and pastoral livestock raising. It has therefore not been possible to separate the contribution of this phenomenon to poor agricultural performance in Sub-Saharan Africa from that of the policy problems identified earlier. There appears to be little doubt, however, that these policy deficiencies have slowed the evolution of ancestral systems into systems more sustainable with higher population density. (A statistical test of this hypothesis is summarized in the Appendix to Chapter 4.)