Sustaining natural resource stocks especially those underpinning the capacity to produce food is key to most definitions of sustainable development. Yet troubling evidence has surfaced of instances where the rural poor were forced to sacrifice long-term sustainability for the sake of near-term survival (Mink 1993; Figueroa 1998). Are such cases special ones, or is rural poverty a driving factor in causing soil erosion, overgrazing, deforestation, and degradation of other natural resources? This paper argues that natural resource sustainability in developing countries is not the result of a direct cause-effect relationship, but rather is engendered by a web of causal factors. Untangling that web entails separating out strands for poverty from those for location-specific natural resource conditions, human institutions, technology, and population. This paper reviews the history of the poverty-environment debate, examines three sets of case studies that shed light on key relationships, and finally proposes policy interventions to promote the sustainability of the natural resources that underpin agricultural productivity.