The researchers took results from the National Health and Nutrition Examination Survey, in which Americans reported their food consumption habits, and then used an Environmental Protection Agency database to calculate the environmental impact of these foods. They did this using what’s called a “life cycle analysis.” As explained in Popular Science:
That process, called life cycle analysis, involves understanding the agricultural processes required at every step of a tomato’s life before it leaves the farm. That includes how much fuel the tractor uses in the field, but also how much energy goes into making the fertilizer and pesticides. Fertilizer, Heller explains, is often one of the bigger contributors. It’s an energy-intensive process that requires making ammonia, and to make ammonia we often use natural gas, so the life cycle analysis for a tomato has to include the natural gas drilling required to make the fertilizer that went into the soil to grow the fruit. And then it also has to include the emissions created by that fertilized soil. Ammonia increases the amount of nitrogen in soil, and that excess nitrogen has the unfortunate side effect of promoting nitrous oxide production. Heller notes that nitrous oxide has 300 times the global warming potential of carbon dioxide, and it’s unavoidably created whenever you fertilize soil.
Interestingly, this analysis does not include transportation from farm to grocery store. As one of the authors is quoted in the Popular Science article,
“The whole local food movement has really emphasized the impact of food miles,” says Heller. “But most of the research points out that that’s not really a huge part of the total. What goes on at the farm is a much bigger piece.”
Unsurprisingly, the foods that are most detrimental to the environment tend to be meat and animal products, partly due to the need to grow crops for livestock to eat. On eating organic produce or pasture-raised beef, the author says,
“Often times those are the things that people’s imaginations jump to, because those are the kinds of choices they’re presented with in the store. Those are small differences, though, and they’re relatively small compared to the large differences we see between food types.”
In other words, meat and animal products are on one end of the spectrum, causing significant harm to the environment, while plant-based foods are on the other.
The graph at the top of this page compares the greenhouse gas emissions of the average and median American diet with that of the top 20%. The authors are correct to emphasize that significant improvements would be made if those people switched to a diet with an environmental impact more in line with the average or median American’s.
This provokes an interesting thought experiment. If our goal is to save animals (and the climate), how do we convince people in the top 20% to change their ways?
To try to persuade someone who consumes such a heavy animal-based diet to go vegan is remarkably unrealistic. It probably happens on occasion. But a far more likely scenario is that person reducing their intake to a level commensurate with the typical American.
This means that promoting veganism among people in this demographic is, quite honestly, a waste of time. In fact, you could argue that it’s harmful, since a different approach would be much more successful in reducing their impact on the environment and animals.
For such people, a reducetarian message is going to be far more palatable than a strict vegan message. This doesn’t mean giving up on trying to convince people to go vegan, but perhaps we need to provide some stepping stones along the way for people who rely heavily on animal foods — a reducetarian lifestyle could be one of those stepping stones.
To put this in perspective, if the top 20% fall in line with the typical American, “we’d save the carbon equivalent of 661 million vehicle miles every day,” as the article states.
How to get started on effecting such change? Heller, one of the study authors, has an idea:
He explains that you can’t think of cigarettes anymore as just one person hurting their own health; it’s inextricably tied to secondhand smoke. If we could start to see our dietary choice the same way—as affecting other people’s health and the planet’s wellbeing—maybe people could start to make better food choices.
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