Abstract The Barbecho Crisis Model (BCM) specifies developmental dynamics for farms at the frontier in Santa Cruz, Bolivia. According to the BCM, farming is profitable whilst forest exists but yields drop and costs increase when cultivation begins in bush fallow and the farm enters the barbecho or fallow crisis. Some farmers than innovate and escape to a consolidated stage with markedly higher incomes. New evidence suggests a number of mis-specifications in the original model. A modified version is presented in which entry into crisis is a progressive effect, related to increased intensity of land use, and includes the role of better access, labour to product price ratios, weed build-up and socioeconomic factors.