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the developing world. The concept and methodology that were developed,
made it subsequently possible for the FAO to undertake assessments of the
potential population supporting capacities at continental scale (FAO 1978).
For the African continent, however, the high altitude areas were not taken
into account.
In this study, an attempt is made to assess the actual and potential population
supporting capacity of the mountainous Kivu landscape in Zaire. The
proposed methodology is based on principles fundamental to any sound
evaluation of land, and takes into account (1) actual farming systems, (2) farm
sizes, (3) yield data at farm level, and from local fertilizer trial plots, and
(4) nutritional requirements. The soil map at scale 1 : 500,000 ( P e c r o t &
L e o n a r d 1960) is used to appraise the extension and agricultural potential
of land that can be used for cultivation. Relief is subdivided into slope classes,
considering a normal soil conservation management. Crop yields obtained
by good farmers on the best soils are considered as reference yields. Yields
used in the calculation of food energy balances are corrected using actual
and potential agro-pedological indices, determined for all mapping units.
Yields are converted into Kcalories using the international nutrition values.
The number of food portions of 2,220 Kcalories (daily calorie requirement
for Zaire) per km2 is assessed and converted into population units.
The methodology has been applied in three sample areas (50 km x 50 km)
representing four different agro-ecological zones in the Kivu : (1) the Butembo
area between 1,450 and 1,800 m altitude, (2) the Lubero area between 1,900
and 2,200 m, (3) the Masisi area above 1,800 m and (4) the South Kivu area
below 1,800 m altitude. The estimated population supporting capacity varies
from 167 to 297 inhabitants per km2 under traditional farming, and from 430
to 594 inhabitants per km2 under a potential intensified management.
2. Procedure
The procedure involves the following steps :
Step 1 : selection of the test areas of 50 x 50 km with different climatic
and pedological conditions. The first test area, Butembo-Lubero, lies on the
equator at altitudes from 1,500 to 2,300 m and includes two agro-ecological
zones. Soils, Acrisols and Ferralsols following the FAO classification (FAO
1974) are mainly developed on sedimentary rocks (shales) of the Urundi system
and some high-grade metamorphic rocks (gneiss and micaschists) of the Ruzizi
system. The second area, Masisi, at altitudes mostly above 1,800 m is located
on the 1°30’ S parallel. The soils (Andosols) are on volcanic ash. The third
area, South Kivu, at altitudes mostly below 1,800 m lies on the parallel 2°30’ S.
Soils, Acrisols and Ferralsols are developed on Paleozoic high-grade metamorphic
rocks, granite and basalt.