タンザニア南部高地における造林焼畑の展開

抄録

This study focuses on a unique mode of slash-and-burn cultivation utilizing artificial forest of black wattle (Acacia mearnsii), which is formed on grass-covered hills in the Southern Highlands of Tanzania. Black wattle was introduced into this area from Australia for the purpose of tannin extraction in the mid-20^th century. This fast-growing tree came to be grown by the native Bena people as fuel wood or as a marker plant of private land. With the penetration of the market economy since the 1980s, the Bena have invented an agroforestry system, with forestry technologies integrated into their indigenous slash-and-burn cultivation system, in order to benefit from the increasing economic value of black wattle.

The new system enables sustainable use of the black wattle forest. Forest regeneration begins just after clearing and burning, as the fire accelerates black wattle germination. Skillful forest management allows the intercropping of finger millet or maize between well-ordered trees for three years. Also, fuel wood and charcoal can be acquired once every ten years when the forest is cleared. Charcoal and local beer brewed from finger millet provides the Bena with cash income. The enormous biomass produced by black wattle, which fixes nitrogen, enriches the soil fertility without the use of expensive chemical fertilizers.

This innovation by the Bena was created through various attempts based on their experience and knowledge accumulated in the process of coping with the socio-economic changes brought by globalization. This case study provides some notable suggestions for endogenous development in rural areas of Africa facing serious environmental degradation and shortage of arable land.