This paper analyzes the role of the main spatial determinants of land use dynamics and simulates past and future scenarios of land use in Paragominas, an old agricultural frontier in Amazonia. Deforestation rates have been reduced since 2007–2008 but soybean cropping and tree plantations are currently undergoing intense expansion. During this transition period, deforestation has shifted from areas close to paved roads to more distant areas and to small farms. Soybean and tree plantations expanded away from paved roads. Soybean crop distribution has a marked influence on the the agricultural potential of the land. Future scenario simulations indicate a loss of almost half of the municipality's forests by 2030 if pre-2007–2008 transition rates are considered. Zero deforestation scenarios show competition between pastureland and cropland, especially on the fertile plateaus. These results highlight the changes in spatial rules and the role of natural factors in an old agricultural frontier.