More than 250 million people in Africa, South America, Oceania, and Southeast Asia depend for the bulk of their food on a practice that is rapidly destroying the world's tropical forests. But this devastation need not be. A new science -- agroforestry -- is being developed which combines food growing with sound forest management, promising a more abundant life for these people.
The destructive practice now employed -- called "shifting cultivation" -- is carried out on roughly 30 percent of the world's exploitable soil.
Originally, it was beneficial. It used to be practiced by small groups of families who lived in open spaces in the forest. They first cleared the forest and then burned the vegetation. Next they tilled the soil lightly and planted or seeded crops. Between harvests, they hunted and fished, collected fruits, and made household utensils from the trees.
When the soil's fertility had begun to wane after a number of years, they left their fields fallow and moved to a new location to repeat the cycle.
Often, they would not return to the same clearing for 30 to 40 years. By that time, the soil's fertility had regenerated as a result of new forest growth.
When the shifting cultivators did return, they cut down the vegetation again and burned it, returning most of its stored nutrients to the soil through the ash. As J. T. Wassink of the Royal Tropical Institute of Amsterdam put it in the publication Agroforestry: "The shifting cultivator grows fertilizer in the form of forest."
If such is the case, how is it that shifting cultivators are destroying forests?
The problem arose with increasing population pressures. The amount of land available to shifting cultivators shrank as intensive, modern farming expanded, as foresters drove them out, as industries and urban areas encroached on forest land, and as their own numbers increased. Some of the farmers also took to growing cash crops.
The result was that "bush fallow" periods became shorter and shorter. The land had less and less time in which to recover its fertility. Eventually, it was depleted. In some cases of extreme overuse, it became useless for agriculture and denuded of trees.
One of the most pessimistic forecasters, Paul Richards, predicted in 1973 that the tropical ecosystem would virtually disappear by the end of this century. More recently (February 1978), the World Bank concluded that the tropical forests would disappear in 60 to 80 years if current removal rates. continued.
The chief cause, most experts agree, is shifting cultivation, the second most important cause being the gathering of firewood.
What then can be done? Can the practice be stopped? If so, what will happen to the millions of people who depend on it for food?
A growing number of agriculturists and forecasters are becoming convinced that a combination of their two disciplines will provide the answer. To this combination they have given a new name -- agroforestry. During the past year and a half, a new international agency, the International Council for Research in Agroforestry, has been set up and has begun operations to encourage i nvestigation and experimentation in the production of food crops, trees and shrubs, and domestic animals on the same piece of land. Among other things, it is hoped that agroforestry can be made into an academic discipline and promoted worldwide.
This will take some doing. In the past, agriculturists and foresters have kept their professional distance from each other. Agriculturists have rarely considered trees a useful part of farmland, and farmers have often ruthlessly cleared their land of trees. Foresters, on the other hand, have regarded forests as more or less their private preserves -- places to grow trees for wood that will have commercial uses, and not places for people (except, of course, themselves).
The idea of these two groups getting together to grow crops and trees on the same land space, perhaps in conjunction with domestic animals, may therefore seen unlikely. Yet growing food crops and trees and raising animals together is just what the shifting cultivators did for centuries. The new breed of agroforesters wants to help them do it more efficiently and productively, while at the same time preserving the natural ecosystem.
there is plenty of evidence that agroforestry works. Here in Kenya, for example, small farmers have been using such techniques for years. A drive into the countryside around Nairobi will provide examples: Croton trees are grown in pastures to provide shade for animals and nectar for bees, and in rows at the perimeter of fields to constitute "living fences," with wire nailed to the tree tunks. Living fences cannot be eaten by termites, succumb to decay, or be stolen for firewood. the do not need periodic replacement, yet they do provide firewood from prunings. Croton trees are also planted in coffee plantations to provide shade for the plants.
Elsewhere, you can see mango trees growing in fields of maize and other crops. They have been planted by the farmer to provide his family with delicious fruit, his animals with shade, and his fire with wood.
Trees planted on farmland can provide many benefits. They can help control erosion, reduce flooding and siltation of streams, and decrease water evaporation in dry areas. Some trees also provide animals with fodder.
Leucanea and Acacia albidam can act as fertilizer factories, because they are legumes. They absorb nitrogen from the air, fix it, and make it available to plants. A single 10-year rotation of the remarkable black wattle tree found in many African countries (Acacia mearnsiim ) can rehabilitate degraded arable land and render it capable of yielding grain crops without adding nitrogen fertilizer. In addition, the black wattle provides one of the richest known sources of vegetable tannin in its bark.
In Malaysia, rubber trees interplanted with leguminous ground cover become tappable four years after planting, compared with six years for trees that are fertilized but planted without legumes. The amounts of nitrogen these legumes make available to the rubber trees is enormous: 900 kilograms per hectare. And although the legumes themselves die after six years, the nitrogen lasts for 20.
In Costa Rica, Cordia, Cadrela,m and Juglansm trees are grown by small farmers in plantations of coffee and cocoa. studies indicate the trees can produce 200 cubic meters of wood within 20 years. One authority estimates that development of a multicropping program on smallholders' lands on only 1 percent of Costa Rica's 1.5 million hectares could support a forest industry with an annual production of 150,000 cubic meters of wood, worth some $6 million.
Examples of agroforestry techniques can be found throughout the developing world, because this was the first kind of agriculture practiced in the tropics. But until now these practices have been largely traditional. Scientific research on them has been virtually nonexistent, because almost all agricultural research carried out in developing countries was on cash crops grown for export.
What is needed therefore is to assess agroforestry techniques experimentally, refine them and quantify them, and then develop new ones. When that has been done, a new science will have been born that could provide the basis for a better life for millions.