Food systems drive a third of greenhouse gas emissions, study estimates A new study provides a comprehensive look at how food systems — from the growing of food to its distribution to its consumption and even its disposal — contribute to global greenhouse gas emissions. It suggests that food systems are responsible for a third of all human-made greenhouse gas emissions, reinforcing previous research that provided similar estimates. According to one expert, the dietary habits of people in developed nations can largely determine the greenhouse gas emissions in low-income countries, although the study does not explicitly state this. Experts say that reform is needed to make food systems more sustainable, and to function within the Earth’s planetary boundaries.