Agricultural activities emit >25% of global greenhouse gases, occupy ~40% of Earth’s land surface, account for >70% of freshwater withdrawals and are the leading threat to biodiversity due to habitat destruction and nutrient pollution. Because of the direct linkages between dietary choice and agricultural production, better knowledge of the relative environmental impacts of producing different foods and of food production methodology (e.g. organic vs non-organic, etc) is integral to reducing the environmental impacts of agriculture. The environmental impacts examined in this analysis are 1) greenhouse gas emissions, 2) land use requirements, 3) energy use, 4) acidification potential and 5) eutrophication potential. A meta-analysis of data from 754 food production systems encompassing 101 foods provides a broad comparison of the environmental impacts of producing different foods. Analyses examining whether food production methodologies affect the environmental impacts of producing a given type of food were conducted. To minimize the effect that agronomic methods and climatic conditions have on the impacts of food production, only production systems within publications are compared when examining different food production methodologies.
For all five environmental impacts examined, plant-based foods consistently had the lowest environmental impacts per USDA serving, kilocalorie and gram of protein. Dairy, egg, poultry and pork have intermediate impacts that are 5-10 times those of plants. Trawling fisheries, recirculating aquaculture and ruminant meats (beef, goat and sheep) often have impacts that are two orders of magnitude higher than those of plant-based foods. The high impacts of animal-based foods are driven by 1) feed inputs necessary for livestock production, 2) emissions resulting from manure management techniques and 3) methane released during enteric fermentation in ruminant systems. Analyses examining food production methodology found that organic and non-organic production systems emit similar amounts of greenhouse gases per unit of food. In contrast, however, organic systems require, on average, 40% more land to produce plant foods and 100% more land to raise livestock than do non-organic production systems. Further, extensive beef systems, greenhouse grown vegetables and trawling fisheries tend to emit more greenhouse gases than do non-extensive beef systems, open field vegetables and non-trawling fisheries, respectively. These data suggest that changing dietary composition is a more effective way of reducing diet-related environmental impacts than is consuming foods produced under different production methodologies.