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A recent study, and the various blog posts and news articles covering the study, seems to make a baffling and contradictory claim: is it possible that adjusting our diets from meat-heavy to produce-heavy could actually result in an increase in greenhouse gas emissions? This flies in the face of almost every assumption and previous study, but the writing is clear as day. One image caption on the study's press release states it in no uncertain terms: "Eating lettuce is more harmful to the environment than eating bacon." A press release from Carnegie Mellon University, in Pittsburgh, Pennsylvania titled “Vegetarian And ‘Healthy’ Diets Could Be More Harmful To The Environment” was published on December 14th. The release came from the university’s press office, and was created to alert people to a new study from scientists associated with the university. Here are some headlines from articles that covered the study, which was first published online on November 24th: These are all wrong, and belie a fundamental problem (perhaps a set of problems) in the world of science journalism. The basic issue is the lack of communication—and often of understanding—between the scientists who do the research and the people who write the press releases, and a further problem of laziness in science journalism from journalists who merely parrot the press releases. The people who write releases are crafting inflammatory, often incorrect documents about scientific research in order to snare the attention of journalists, who all too often don’t bother looking into the research at all. And why bother? When you have to write six or eight posts a day, and a press person at some university writes up an attention-grabbing headline, it’s an awful lot easier to just rewrite the release than it is to actually look into whether the document accurately represents the research—let alone whether the research itself is any good. The latest victim of this trend is Michelle Tom, who co-authored the Carnegie Mellon study we’re talking about here. Her title was “Energy use, blue water footprint, and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the US.” That report, which looks into the environmental effects of different types of food, was retitled “VEGETARIAN AND “HEALTHY” DIETS COULD BE MORE HARMFUL TO THE ENVIRONMENT” by Shilo Rea, a director of media relations at Carnegie Mellon, where Tom is a Ph.D candidate. (Shilo “represents the College of Humanities & Social Sciences, including the areas of psychology, decision sciences, behavioral economics, education and literature,” according her bio. She did not respond to requests for comment.) “It seemed to me like they were really trying to be controversial.” “I think the title of this press release is definitely misleading and is not an accurate portrayal of our research,” Tom told me yesterday by phone. She went on to say that she wished she’d gone further in putting her foot down about the wording of the release. “I never met the person who wrote this [press release],” Tom said. “I did take a look at it and made a few revisions. I should have had them change that title.” “It seemed to me like they were really trying to be controversial,” said Kai Olson-Sawyer, a Senior Researcher and Policy Analyst with the GRACE Communications Foundation, a non-profit that studies the connections between food, energy, water, and emissions and campaigns for sustainable options. (He focuses on water use.) After drilling down through the study and talking to Tom and to Olson-Sawyer, here’s my understanding of what the study is actually trying to say: Not all vegetables and fruits have an equal impact on the environment (the study looks at water use, energy use, and greenhouse gas emissions), and it’s even true that with some very careful rejiggering, you can create a possible produce-heavy diet that is worse for the environment than a meat-heavy one. In her study, Tom sets up three possible scenarios, all related to the current caloric intake of the average American (they figured this at about 2,390 calories per day on average, with about half again that much in food waste) and the United States Department of Agriculture’s (USDA) recommendations regarding the percentages of each food group (grains, fruits, meats, vegetables, dairy) we should be eating. Those are all laid out in the USDA’s current nutrition guidelines, though Americans on average still have a ways to go before the reality matches the recommendations. According to Tom’s findings, only Scenario 1 would result in a positive effect on the environment. This seems totally unexpected; we are told, again and again, that eating more fruits and vegetables and grains is good for the environment, that livestock emissions are a huge problem, and that changing our diet to be more like the USDA’s recommendations—meaning, less meat—would have a positive effect on the environment as well as our bodies. Tom’s study says this isn’t the case, and journalists took notice. The press release, and the coverage that followed, relied heavily on one very weird comparison: lettuce and bacon. This seems to come from one quote given by Paul Fischbeck, one of Tom’s advisers: “Eating lettuce is over three times worse in greenhouse gas emissions than eating bacon,” he said, according to the release. You can see why a media person might have grabbed on to this—the two items fairly scream “healthy” and “unhealthy.” But to compare them using the information provided by this study is…insane. The study is in fact not saying anything of the sort, and the list of caveats needed to make that statement mathematically work would run pretty long. You’d have to compare them by calorie count instead of by weight or by nutritive benefits. You’d have to assume that any human would replace a protein source with a mostly water-filled leafy vegetable, which not even the USDA is recommending. (The USDA’s dietary guidelines do, in fact, include meat.) And you’d have to assume the figures on pork processing presented in the study are accurate, which I am not sure they are (given the lack of available data on full lifecycle emissions, which I’ll get into in a bit), and that the lettuce was grown in California. (Not a bad bet, but not a given: 90 percent of the country’s leafy lettuce comes from California, and 83 percent of its Romaine lettuce. If you’re eating lettuce from anywhere else, these figures are way off, which I’ll get into in the Blue Vs. Green Vs. Grey Water section.)
