Canadian prairie grain production potential is tied to a number of institutional, resource and environmental factors. In estimates of production, potential researchers have resorted to the use of a variety of assumptions regarding bio-physical and technological conditions. Generally, these estimates fail to incorporate the effects of resource and environmental constraints upon productive capacity. The intent of this paper is to show how grain production in the prairie provinces, with ostensibly a large potential for growth and expansion, can, through the operation of a variety of constraints, lose much of that potential. A simulation model is developed for a 25-year period in which projected growth trends for cultivated area and yield are successively modified and adjusted to account for the effects of various forms of land degradation, loss of agricultural land and climatic change.