1. Introduction
Drought, unbridled population growth, declining productivity,
land degradation and abject poverty contribute
to the recurrent famines in many parts of tropical and
subtropical countries (TSC). Survival needs supersede
concerns for resource conservation and problems of
biodiversity depletion and large-scale degradation of
natural resources are overwhelming. Ethiopia is an
emblematic example of a TSC rural country whose economy
is mainly based on renewable resources
(pastoralism and/or agriculture of subsistence). In most
parts of Ethiopia, problems related to maintaining natural
resources are critical and alternative livelihood options
are limited (Egziabher, 1990). A long history of land
clearance and sedentary agriculture has changed the vegetation
cover in the Ethiopian highlands. Esayas (2000)
has shown that a quarter of the highlands of Ethiopia are