Food Choices And GHG Emissions: The Individual Nitty Gritty

As many studies have explored over the past decade and more, agriculture is a key contributor to many environmental problems, including climate change, biodiversity loss and ecosystem degradation. Researchers suggest that demand-side reductions will be necessary for the U.S. to meet the COP-21 Paris Agreement on combating climate change. In this study, scientists came together to create a food impact database evaluating individual self-selected diets according to their environmental impacts.

How can such a database be reliably created? The researchers argue that individual-level data are essential for better modeling of dietary change policies, as they allow for understanding the range of impacts within a population. They are especially useful when linking demographics (e.g. age, gender, ethnicity, education, nutritional knowledge, environmental attitudes, etc.) to the dietary behaviors of these groups, and their associated environmental impacts. Specifically, 24-hour dietary recalls have been shown to provide good detail about foods consumed, and they tend to be less biased than other types of questionnaires.

The researchers conducted a comprehensive literature review, which produced 1645 entries (combinations of food types and production scenarios) from hundreds of unique peer-reviewed sources. Although undeniably thorough, the review still lacked some information: cross tabulations of certain production methods were found to be unavailable or unreliable. Furthermore, previous studies found that self-reported diets typically understated actual food intakes.

Since animal-derived foods are typical in Western diets, the authors evaluated which products are responsible for the highest GHG emissions. In the U.S., 80.6% of meat GHGs come from cow meat, 9.5% from chickens and 8.5% from pigs. Out of the 5 most intensive GHG-causing foods, 4 were animal product groups. The fifth were beverages. Interestingly, fruit and vegetable juices make up 33% of the GHG emissions in this group, which overall was shown to be of significant impact, but otherwise underrepresented in previous studies.

Another interesting finding: the top 20% of diets with the highest carbon footprint accounted for 45.5% of the total diet-related emissions in the U.S. In fact, even after normalizing the impacts according to caloric intake, GHG heavy diets are responsible for five times higher emissions compared to the least GHG intensive U.S. diets. If the whopping 44.6 million U.S. citizens with the most carbon-intensive, shifted to the mean diet presented in this paper, it would lead to a one-day reduction equal to avoiding 661 million average car miles on a given day.

Based on the above data and more, the researchers note that campaigns targeting dietary shifts offer a significant opportunity for state, city or business-wide anti-climate change action. As most of us know, however, getting people to change dietary behavior is notoriously challenging. The paper suggests that even more effort would be dedicated to identify effective strategies for influencing dietary shifts.

Animal advocates will undoubtedly benefit from another study revealing the environmental concerns associated with animal-based foods. The creation of an individual food item database could allow for more targeted advocacy for specific shifts in dietary habits. Furthermore, advocates might want to reflect upon the ‘environmental inequality’ among self-selected diets and select target groups accordingly.