ABSTRACT
Managed food production systems started with the early civilizations that saw humankind change its lifestyle from hunting and gathering of food to agriculture. This transformation was accompanied by a reduction in the number of plant species on which man depended for essential nutrition. Although the hunting and gathering stage was characterized by man’s dependence on food from a wide range of trees, shrubs, and herbaceous plant species, a limited number of mainly herbaceous annual plant species emerged as staple foods in different parts of the world with the advent of managed crop husbandry. Intensification of crop production during the last century with inorganic fertilizers and agrochemicals resulted in large areas of natural vegetation, with a predominance of trees and shrubs, being replaced by monocultures of mainly annual crops. By the latter part of the twentieth century, several of these monocultures had developed problems of sustainability such as land degradation and declining yields. It was in this scenario that agroforestry, which is the deliberate mixing of trees with agricultural crops, emerged as a distinct scientific discipline (Bene et al., 1977) by the beginning of 1990s, as a set of practices (Nair, 1990, 1993; Sanchez, 1995) that ensures sustainable food production while conserving and replenishing the natural environmental resource base.
