Diet choices and production matter more than food miles: study

Christopher Weber and Scott Matthews conducted a study - to be published in an upcoming issue of the journal Environmental Science & Technology -​ which found that replacing meat and dairy products once per week with chicken, fish or vegetables has about the same effect as eating an entirely locally sourced diet. The findings are noteworthy for manufacturers and producers looking to market to ethically-mind consumers, or looking to reduce their own carbon footprint. The term 'food miles' refers to how far food has to travel before it is set on a plate. It has increasingly crept into the spotlight as a means of making dietary choices that use less transport resources and thereby do not have a harmful impact on the environment. In their research however, Weber and Matthews added to existing literature on food miles by examining the impact food production has on the environment as well. They subsequently found production actually makes more of an impact than transportation. They wrote that although food is transported great distances - averaging 1640km for delivery and 6760km along the supply chain -the greenhouse gas (GHG) emissions related to food stem largely from the production phase. This phase contributes 83 percent of the average US household's CO2 emissions for food consumption, according to the study. Meanwhile transportation represents only 11 percent of supply chain GHG emissions, with final delivery from producer to retail contributing only four percent. "Different food groups exhibit a large range in GHG-intensity; on average, red meat is around 150 percent more GHG intensive than chicken or fish,"​ wrote the authors, who are specialized in civil and environmental engineering, and public policy. "Thus, we suggest that dietary shift can be a more effective means of lowering an average household's food-related climate footprint than 'buying local'." ​ The researchers used an input-output life-cycle assessment to track the total life-cycle GHG emissions associated with producing, transporting, and distributing food consumed by US households. In their study, they included all food and nonalcoholic beverages, and the related emissions of greenhouse gases in the supply chain. However, Weber and Matthews acknowledged that the scope of the research does not give a full picture of either what motivates consumer food choices, or further environmental impacts associated with food. "…it should be noted that this analysis only examined climate impacts, which are only one aspect related to food choice, and are only one dimension of the environmental impacts of food production. Food choice is based on a variety of factors, including taste, safety, health/nutrition concerns (both between different food types and among food types, i.e., organic vs conventional), affordability, availability, and environmental concerns,"​ they wrote. Those who buy locally often do it for a variety of reasons not necessarily associated with a concern for food miles, state the authors, and as such say food policy must also be broader in scope if the environmental impact of the industry is to be tackled. "Though this analysis shows that some food types are much less GHG intensive than others, any attempt to change consumer behavior based on only one dimension of food choice is unlikely to be effective,"​ concluded Weber and Matthews. Source: Environmental Science & Technology​​​Published online ahead of print, doi:​ 10.1021/es702969f​"Food-Miles and the Relative Climate Impacts of Food Choices in the United States."​. Upcoming publication. Authors: C.L. Weber, H.S. Matthews