The genocide in Darfur, Sudan is the first major humanitarian crisis of the 21st century. Over 2 million people have been displaced and tens of thousands have been killed. Popular explanations of the conflict root it in racism and prejudice orchestrated by the Sudanese government and abetted by the world community’s negligence. While the complicity of the Sudanese government is evident, a closer analysis of the sequence of events suggests that the crisis is rooted in local conflicts over material resources brought about by an ecological crisis. Standard social theory has proven inadequate for analyzing the grass roots nature of the Darfur crisis. We have developed a flexible agent-based computer simulation of pastoral nomad/sedentary peasant interaction (NOMAD) that can be adapted to particular environmental and social settings. Our focus on how environmental and material factors condition individual agent response allows us to model how collective behaviors (mass raiding, genocide) can emerge from individual motives and needs. Many factors influence the conflict in Darfur (ethnicity, global politics, Sudanese politics). However, our simulations reinforce the analyses of some social scientists that argue the Darfur crisis is the inevitable result of the breakdown of land use in the face of growing populations, marginal habitats, and an unprecedented ecological crisis.