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Pursuing the Paris Climate Accord Goals: Martin Heller

Martine Heller talks about sustainable diets and the process of producing food in the context of the Paris Climate Accord.
Welcome back to this teach out on food sustainability. I’m here again with Dr. Martin Heller to talk about the Paris climate accord and carbon emissions, and how we think about our food choices and how they impact those overall emissions. So jumping into it, I know that you recently co-authored a study that explored the variability that there is between emissions that are associated with a variety of American diets, and you found a striking result here that 46 percent of total emissions from food came from the diets of just one fifth of the population. Can you tell us a little bit more about that finding in that study. Sure. So that’s utilizing diet data from the National Health and Nutrition Examination Survey.
So this is an ongoing survey that we conducted in the US to ask people about what they’re eating and about their health, and a lot of other associated questions, but it’s really the the best source of information in the US that we have for understanding people’s diets and what they’re eating. The big advantage of using that to look at a question like this is, like you said, we can begin to look at what the spread is rather than just looking at a single number at the the average US diet. We can begin to look at how the variation in diets in the US influence that carbon footprint.
One of the striking things that we found is just how much that high entail. The diets that are very high and greenhouse gas emissions contribute to the overall total. So like you said, that the top fifth something like 46 percent of the total, there’s like an eight-fold difference in the contribution from that highest fifth, the highest 20 percent of the population to the lowest 20 percent of the population. So pretty big spread there. Can you tell us a little bit more about these groups and who is in which groups, and how you partition that? Sure, Yeah. That’s a challenging thing to generalize.
I mean the partition simply by linking environmental impact, linking greenhouse gas emissions associated with producing different foods to those individual diets, and so then assigning a carbon footprint, greenhouse gas emissions associated with that given diet, and then just ranking them based on that total. So that’s what gives the order, and then we divide them evenly up into fifths and can start to look at what’s going on in those groups. Because of the nature of this data, statistical stuff, it’s difficult to just hone in and look at individuals, you have to look at them in an aggregate. So we can start to look at what’s driving those differences.
A big part of it is the folks in those high impact diets simply are eating more, that contributes a lot. But even if we normalize by the caloric intake, that difference between the high-impact diets and the low impact diets is still a factor of five. So the composition of the diets between those two groups is a big contributor as well. Largely, what we see is the amount of meat, and in particular, the amount of beef in the diets is a large driver. So more meat in the high-impact diets, more likely to be beef verses poultry in the lower impact diets. It’s helpful.
So thinking back to the previous segment, where we were talking about how small decisions can have a really large positive impact on the environment in terms of your food choices. Looking at that 46 percent is a huge opportunity there to make even marginal changes for that group can have a really big impact. Yeah, just to put those numbers in perspective, we looked at a hypothetical diets shift, it’s just a what if. What if we were able to bring the greenhouse gas emissions of those upper fifth diets just down to the average of the total population?
So if we’re thinking about that in terms of food intake, again, picking on beef because that’s a big driver of what’s going on up there, but the average beef intake in that upper fifth was something like a third of a pound a day. That’s a fair amount of beef. The average for the whole population was I think 51 grams. So that’s something like a quarter pound every other day. But, that gives you a little sense of the kinds of reductions we’re talking about here. Of course, beef isn’t the only thing that’s driving those changes, but it’s a big part of the driver and gives you a little sense of what the scale is.
But, what we found is, if we are able to bring that upper fifth down to the average and assumed that that could happen every day of the year, it would bring us 10 percent closer to reaching our Paris accord agreement. So I think it starts to put in perspective that the role that diets shift can have in climate action. These net numbers or those types of changes really do matter from the broader perspective of our overall US emissions. Sure. That’s really striking, especially thinking about across all sectors not just looking at food, I mean there’s so many different behaviors that an individual can change to have a positive impact on their own contribution to carbon emissions.
As we’re looking for these marginal decreases across the board, they add up, which is great. It’s really exciting to see those opportunities. So I wanted to talk a little bit about the concept of food miles. A lot of people think about the transportation associated with fluid as having a really large emissions impact. So we see a movement or an eating local and supporting things that are grown within certain amount of miles from where you live, right? Yeah. But, I’m curious to hear a little bit more from your perspectives looking at the life-cycle analysis of how food is produced, and also taking into consideration pre-production and production, as you mentioned earlier, what are your thoughts on that? Yeah.
I’d love to start by saying that I’m a huge proponent of local food. I think that growing food among our neighbors, greatly having food and agriculture as part of our community is a huge importance. There’s lots of benefits in terms of nutrition and just the quality of food that you can get by having it grown locally, but what we see when we look at these life-cycle studies of food production is on the whole those transportation miles, those food miles don’t contribute all that much to the overall total. Again, there’s a lot more emissions associated with the actual on-farm production.
Again, on the whole, the transportation is probably in the like five to 10 percent of total emissions associated with our food. That’s not to say that those food miles don’t matter, but if we are going to make a choice of choosing something because it’s local or choosing something because it’s a low emission plant-based food rather than an animal-based food, you’re going to see a much greater reduction by choosing a different food than by choosing the local one. That’s great. I mean that’s really helpful. So thinking about individual changes that we can make to help take that step in the right direction, thinking about growing a garden in your backyard.
So going out and that really cuts down on the food miles. So trying to reconnect there to your local food economy in a different way is meaningful, and understanding that the production is going to be a huge part of where our food comes from and where a lot of the missions are, but knowing that wherever you want to buy your food, you have these decision points. You have these moments where you can weigh those options. So I think that the critical thinking skills associated with that are super important.
So from what you’ve seen in your research, what do you think the best way that we can continue on this path to reduce our carbon emissions as it relates to everything that we’ve discussed in this segment? Sure. I really think that the two standout pieces are reducing food waste, and that’s a tricky one. It means changing our relationship with food and a lot of ways, and changing our behaviors around how we purchase, and what our thoughts are about leftovers, and how we prepare food and all of these other bits. But, I also want to make it clear that when I’m talking about reducing food waste, I mean not necessarily just composting it, I mean that’s a great thing.
If you have to waste food, it’s better to dispose of it in a proper way, then send it off to the landfill. But again, the impact associated with that, the greenhouse gas emissions associated with it comes from production. So regardless of how we dispose it, we’ve already invested those carbon emissions. So that’s a big piece. The other one is thinking about our diet and the composition of our diet, and eating less animal-based foods. Again, there’s plenty of evidence that demonstrate that the benefits of that from an environmental perspective as well as a health perspective.
I think we’re always going to have cultural discussions about what kind of diet is most health promoting and best for weight reduction, and all these other things. At the end of the day, those are individual choices, but we do know that reducing animal-based foods in your diet can have a noticeable impact on your carbon footprint. All right. Well, thank you so much for joining us Martin, and thank you for joining us. We look forward to continuing the conversation and the discussion forums.
A recent study (optional reading), co-authored by Martin Heller, explored how much variability there is in the GHGs of American diets and found that 46% of the total emissions from food came from the diets of just 1/5 of the population. In this segment we will talk about how much our food choices individually and collectively, contribute to total GHG emissions in the United States. We also discuss the concept of “food miles” and where the majority of our food-related GHG emissions come from.
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Sustainable Food Teach-Out

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