Food produced in the tropics comes with high carbon emissions and low crop yields, according to a new study in the Proceedings of the National Academy of Sciences (PNAS). In the most comprehensive and detailed study to date looking at carbon emissions versus crop yields, researchers found that food produced in the tropics releases almost double the amount of carbon while producing half the yield as food produced in temperate regions. In other words, temperate food production is three times more efficient in terms of yield and carbon emissions.