Previous - Next
The end product of the AEZ study covering the developing world is a computerized inventory of the land resources of developing countries and one form of interpretation, namely concise data on the area of land variously suited to the production of 11 different crops, under two levels of inputs. These data can be simply converted to give the production potential of any individual crop, or mix of crops.
The AEZ methodology is scale neutral and, providing sufficiently detailed data are available on climate and soil, the technique can be applied on a much larger scale to individual countries or even to administrative areas within them. These applications are now becoming increasingly important (see pages 25-31).
For example, it is relatively simple to calculate the crop mix which would give a region or country maximum calorie production. This is an important application of the AEZ methodology for development planning. Once the requirements or goals are established, the potentials can be calculated, and the investment and inputs required to realize them can be assessed.
The first major application of the AEZ technique by FAO was to calculate the potential population-supporting capacity of the land of the developing world, by agro-ecological zone, by country and by region. The steps involved are illustrated below.
Basically, the data on crop potentials are used to calculate the maximum calorie production possible for each agro-ecological zone. These are then modified according to the assumptions required, including assurance that the land also produces at least the minimum amount of protein needed. A knowledge of the per caput calorie and protein requirements of each country enables an estimate to be made of the total population that can be supported, and this figure is then compared with current and estimated year 2000 populations.
The results of this study have already been published (FAO/IIASA/UNFPA, Potential population-supporting capacities of lands in the developing world, 1982, FPA/INT/513). The study showed, for example, that even in 1975 some 55 of the 117 countries studied could not support their populations from their own land resources with low-input production systems. The area of these countries was 32.5 percent of the entire developing world. And the population that exceeded the critical carrying capacity was about 270 million people.
Eight steps to population supporting capacity
However, the situation changed dramatically if the level of inputs was improved. By the year 2000, the number of countries unable to support their own populations was calculated as:
• 65 countries if low inputs were applied;
• 36 countries at intermediate inputs;
• 19 countries even if high inputs were applied.
Many of the latter are small territories with limited land resources.
The results again illustrate the critical importance of input level in all AEZ-type studies. Currently, most African countries use little more than low inputs; those in Latin America are about one-third of the way toward intermediate levels of inputs; those in Southeast Asia are more than half-way toward intermediate input levels.
The population-supporting capacity study not only took the AEZ methodology a stage further, but expanded its original base in a number of important ways.
First, the original 11 crops were increased to 15: barley, groundnuts, banana/plantain, sugar cane and oil palm were added to the list (cotton, which is not a food crop, was dropped). Production of livestock from grassland was also included. Second, the study was not restricted to rainfed crop production but included actual and projected production from irrigated land. Third, allowance was made for nonagricultural land requirements. A simplifying assumption was made here, namely that the average need for non-agricultural land is equivalent to 0.05 ha/person. Finally, the study included requirements for fallow periods, limitations imposed by uncontrolled land degradation and estimated reductions in production caused by waste and the need to conserve seed (none of which was included in the original study). Calculations were also made for an additional intermediate level of inputs.
These are only some of the sophistications that can be added to the original AEZ methodology. Many further improvements are now being built into the technique as it becomes more widely applied at the country level. For example, if AEZ-type studies are carried out at district or even project level it becomes possible to quantify fairly exactly the requirements for non-agricultural land. National data on present and projected areas needed for forest products, national parks, and cash crops can be fed into the program to provide a more precise evaluation of the area of land potentially available for cultivation.
In addition, the existence of regional and national land inventories enables many different kinds of study to be carried out at the subregional as well as the regional level. One such study has investigated the potential for wheat production in Africa, where many traditional foods, particularly in urban centres, are being abandoned for wheat consumption.
This is a costly trend because relatively little wheat is grown south of the Sahara. Much of what is consumed must therefore be imported. To what extent would it be beneficial for African countries to become self-sufficient in wheat? The answer depends on whether policies are designed to maximize calorie production or income. But, as the box below shows, complete self-sufficiency for wheat is neither feasible nor desirable for most African countries.
Wheat field in Tunisia. Wheat grows well in some North African countries but conditions south of the Sahara often limit yields severely.
Wheat consumption in Africa is growing fast. So are wheat imports. Should Africa, therefore, grow more wheat in the future? And, if so, what ecological and economic results would this produce?
These questions have been studied using the AEZ methodology. Calculations were made for three different assumptions:
1 wheat is grown only where it maximizes calorie production;
2 wheat is grown only where it maximizes agricultural revenue and
3 wheat is grown wherever conditions permit.
Using low inputs, rainfed wheat can be grown on only 37.7 million ha in Africa, out of a total land area of 3033 million ha. In North Africa who'. growing conditions for wheat are best, 13.6 million ha (2.4 percent) out of a total of 574 million ha are suitable for rainfed wheat. In the rest of Africa, an area of about 2460 million ha, only about 24 million ha (1.0 percent) are suitable for the crop nearly 17 million ha in the tropical highlands of countries such as Ethiopia, Kenya and Tanzania, and some seven million ha in southern Africa.
In North Africa, it would pay to plant wheat in preference to other crops on nearly two-thirds of all the land suitable for wheat. This would provide about 80 percent of the maximum possible wheat production. South of the Sahara, where land is less; suitable for wheat, a plan to maximize revenue would include only enough wheat to grow 11 percent of the maximum possible production.
The study shows that, considering the whole of Africa, it would be economically viable to grow only 17.6 million tonnes of wheat in Africa - against an estimated need for wheat of 29 million tonnes in the year 2000. However, only nine million tonnes per year were produced during 1979-81, and 13.6 million tonnes in 1988.
If the aim were to maximize calorie production, only 16.3 million tonnes of wheat would be grown in Africa. However, some 70 percent more wheat would be grown in sub-Saharan Africa than if maximum revenue were the aim, a figure nearly five times higher than production in 1978-80.
The main conclusions of the study are that wheat self-sufficiency is economically viable for very few countries in Africa. In most other countries of the region, calorie production and agricultural revenue can be increased more efficiently by growing other crops.
