How does climate change affect the production of native Grains of America? There is an impact of climate change on rain-fed crops productivity and its association with alimentary security. This study analyzes how events such as global warming, unsustainable agriculture or intense droughts caused by lack of water, affects the production of quinoa in Bolivia and maize in Mexico. Our estimates suggest that climate variability will modify agriculture yields (of maize and quinoa) per hectare depending on the agricultural season, the municipality and the ensemble model used to project climate change scenarios. The study indicates tremendous heterogeneity in areas and regionally. Based on the cobweb phenomena approach, it is suggested that the producers base their decisions for their future production on the assumption that present prices will continue. If this is not the case, rigid price expectations may produce irreversible supply conditions in the short run. These prices are set by the available supply of the grains. Their production is completely determined by the producers’ response to price, under conditions of pure competition.