Agrifood systems divert resources from biogeochemical cycles (e.g., carbon and nitrogen cycles) to produce food, with major negative effects, including global warming. Global warming is changing water distribution and temperatures that will have mostly negative effects on agrifood systems. Changes in the agrifood systems could make major contributions to decreasing greenhouse gas emissions (e.g., sequestering soil carbon with organic fertilizers and reducing tillage; reducing fossil fuel use; reducing food waste; and reducing animal, processed, and imported foods in diets). These changes will require changed assumptions and behaviors, but could also have major synergistic effects. For example, in addition to reducing greenhouse gas emissions, changing diets could improve health, reduce medical costs, reduce water consumption, and free large areas of land devoted to animal food production.