About half of tropical deforestation is commonly explained by the expansion of traditional agriculture (shifting cultivation). This article first questions the share of responsibility assigned to traditional agriculture — it may well be overestimated because of unclear definitions, uncertain estimates, and potential political biases. Second, a simple framework based on a theory of land rent capture is developed to explain agricultural expansion. The framework is applied in the study of recent changes in shifting cultivators' adaptations in a lowland rainforest area in Sumatra, Indonesia. Increased rubber planting and expansion into primary forest are seen as a response to increased rubber profitability and (expected) land scarcity, and as a race for property rights. Government land claims have had significant multiplier effects on forest clearing through changes in farmers' expectations and in initiating a self-reinforcing land race.