This paper is an interdisciplinary attempt to address the relation between the population with its social interactions, and the resource base of the surrounding landscape. It tries to merge a sociological and anthropological approach in explaining population and demographic conditions with an ecohydrological approach in explaining fundamental environmental functions and phenomena in the landscape. It draws attention to the fact that Third World development often has to take place under genuine water scarcity. At the same time, livelihood demands and production activities necessitate manipulations of soil, vegetation and water, in spite of the environmental vulnerability typical of low latitudes. This calls for skillful balancing methods between intended benefits and unavoidable side effects to secure environmental sustainability, protection of land fertility being crucial.