Your resolution to eat healthy is saving the earth (more than you realize)

SOURCE: Camilleri, A. R., Larrick, R. P., Hossain, S., & Patino-Echeverri, D. (2018). Consumers underestimate the emissions associated with food but are aided by labels. Nature Climate Change, 1.

Visions of Sugarplums

This winter I laughed with family over a traditional Swedish dinner at my aunt’s house and made tea ring dough on Christmas eve from my great aunt’s recipe. I caught up with childhood friends on New Year’s Eve over homemade fondue, and I talked to my brother about his first semester of college while making midnight naan.

It wasn’t until I read a recent article by Dr. Adrian Camilleri (University of Technology Sydney) and his colleagues at Duke University that I began to consider the carbon footprint of our holiday food traditions.


Food and Carbon

The global food system is responsible for a whopping 20% of greenhouse gas emissions — roughly equivalent to all of the household electricity usage in the United States.

These food-related emissions come from a lot of different sources, but one of the main contributors is — no joke — cow burps! Cows burp (and pass gas) enough to be a globally significant source of greenhouse gases. Experts estimate an average cow emits at least 100 liters of methane a day (here’s why).

Some of the other sources of greenhouse gas emissions include refrigeration, transportation, fertilizer production, and land conversion.

In general, those fruits and vegetables that we’re all trying to eat more of in the New Year are way better for the environment. Meat has an especially big impact because you have to factor in all of the greenhouse gases associated with producing food for the animal to eat.


Failing the Test

Dr. Camilleri and his colleagues wanted to see how well people can estimate the greenhouse gas emissions associated with their food, so they set up a quiz. They told their participants that when you use a 100-W incandescent bulb for one hour it emits ‘100 units’ of greenhouse gases. Then they asked people to compare a serving of 19 different foods to that incandescent bulb. To see whether people are better at estimating the emissions associated with food or other energy-related parts of their lives, they also asked everyone to compare the same light bulb to 18 household appliances.

What did they find? Bad news. People weren’t great at estimating the amount of energy that the household appliances use, but they were way worse when it came to food.

The participants generally put the foods in the right order (for example, beef leads to more greenhouse gas emissions than almonds, which in turn lead to more emissions than corn does), but they vastly underestimated how much worse the high-emission foods are than the low-emission foods. The extent to which they underestimated emissions was much greater for food than for household appliances.

A graph comparing people's estimation of the greenhousegas emissions associated with food and household appliances to the actual values. People underestimate the greenhouse gas emissions associated household appliances, but are much worse when it comes to food.
People underestimate the greenhouse gas emissions associated household appliances, but we are much worse when it comes to food. Accurate estimates would lie on the grey line. SOURCE: Camilleri et al. 2019. Used with permission.
A Bright Idea

Startled by these results, Dr. Camilleri and his colleagues wanted to see if there is any way to help people better understand the impact of their food. They guessed that if people had a better understanding of the magnitude of the emissions produced by their food, they might choose to eat food that has a less dramatic impact on the environment. So the researchers designed a little label that tells people how much energy the food item takes to produce, in light-bulb-equivalents, and gives the food an energy ranking from green to red.

To see if the label works, they brought in more participants and gave everyone a menu of six types of soup: three with beef and three without. All of the menus included the name of the soup, an image, the serving size, the price of the soup, and nutrition facts. Half of the menus also included the label they designed.

In the end, participants who were given the labels decided to purchase fewer cans of beef soup than participants who didn’t have the label, indicating that the label was very effective in helping people choose food with a lower carbon footprint.

When participants were asked to estimate the emissions associated with beef soup and vegetable soup, participants who had seen the label gave better estimates than participants who did not.

A schematic diagram. In the bottom left is a label that indicates the number of light-bulb equivalents of greenhouse gases that are produced in making one serving of soup. The label also has a color scale that says how large the carbon footprint of this soup is relative to other soups. When people saw the label, they gave a higher (more accurate) estimation of the ratio of beef to vegetable greenhouse gas emissions and purchased fewer cans of beef soup.
When participants were presented with a label like the one shown in the bottom left, they gave a better estimate of how much more greenhouse gasses are released in the process of producing beef than in the process of growing vegetables. This caused them to ultimately buy fewer cans of beef soup. SOURCE: Camilleri et al. 2019. Used with permission.


A Small Step Forward

A small label like the one proposed in this study can help people make choices that are more in line with the values they already care about. Because food accounts for 20% of greenhouse gas emissions, our food choices can collectively have a significant role in slowing the rate of global climate change in years to come.

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Abigail Lewis

I am a Ph.D. student studying freshwater ecology and biogeochemistry at Virginia Tech. Whenever possible, I enjoy thinking and writing about the role of science in society, including community-based science, science communication, and science for the public good. In between rehearsals, hikes, and long dinners I am working to build a career that will address environmental issues and build a more inclusive scientific community. Twitter: @lewis_lakes

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