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“Tell me what you eat and I will tell you what you are.” That’s what the French lawyer Jean Anthelme Brillat-Savarin, who happened to have a deep love of gastronomy, wrote in 1825. A century later, a diet-hawking American nutritionist named Victor Lindlahr rendered it as: “You are what you eat.” I propose revising it further: Tell me what you eat and I will tell you how you impact the planet. Most of us are aware that our food choices have environmental consequences. (Who hasn’t heard about the methane back draft from cows?) But when it comes to the specifics of why our decisions matter, we’re at a loss, bombarded with confusing choices in the grocery-store aisles about what to buy if we care about planetary health. Are organic fruits and vegetables really worth the higher prices, and are they better for the environment? If I’m a meat eater, should I opt for free-range, grass-fed beef? Is it OK to buy a pineapple flown in from Costa Rica, or should I eat only locally grown apples? The science of food’s ecological footprint can be overwhelming, yet it’s important to understand it. For starters, in wealthy societies food consumption is estimated to account for 20 to 30 percent of the total footprint of a household. Feeding ourselves dominates our landscapes, using about half the ice-free land on earth. It sends us into the oceans, where we have fished nearly 90 percent of species to the brink or beyond. It affects all the planet’s natural systems, producing more than 30 percent of global greenhouse gases. Farming uses about 70 percent of our water and pollutes rivers with fertilizer and waste that in turn create vast coastal dead zones. The food on your plate touches everything. “If you look at the heavy-hitter list of global-scale changes that are human induced, how we feed ourselves is invariably near the top,” says Peter Tyedmers, a professor at Dalhousie University’s School for Resource and Environmental Studies (SRES) in Halifax, Nova Scotia, who has been studying the world’s food systems for 15 years. “But the great thing about food is that we have choices, and we have the opportunity to effect change three times a day.” So what does a sustainable diet actually look like? I’ve thought a lot about my food choices and became a vegan a few years ago, but I still don’t know all the answers. So I set out to find them. I didn’t go hunting for a crazed notion of perfection. I was simply looking for an attainable way to eat—whether you’re a vegan, a vegetarian, or an omnivore. Here’s what I discovered. One of my first stops is with Tyedmers. On a surprisingly warm evening for September in Halifax, he and dozens of SRES students are gathered on the back deck of a modest clapboard house to celebrate the start of the term. The only strange thing is what I see on many plates: hamburgers. Admittedly, chicken and veggie burgers are also available. But the fact that an environmental-studies cookout features beef—perhaps the most vilified of all foods in terms of planetary impact—reminds me of the deep tension that exists between the urgency of what we know and the inertia of how we live. We love our meat. And any conversation about food and sustainability has to start with it. Before I arrived, Tyedmers pointed me to a few landmark studies, the results of which are hard to ignore. Eighty percent of the world’s agricultural lands are allocated to animals, either for pasture or to produce food for them. More than 20 percent of all water consumed is used to grow grain to feed livestock. A 2013 United Nations Food and Agriculture Organization study estimated that livestock accounted for 15 percent of greenhouse-gas emissions, about the same as the entire global transport sector. Other analyses, which argue that the UN estimate doesn’t adequately account for things like the CO2 produced by the respiration of tens of billions of farm animals, estimate that livestock might be responsible for up to 51 percent of global emissions. “Meat is heat,” environmentalists like to say. The type of meat you eat matters, too. A 2011 life-cycle analysis by the Environmental Working Group, a Washington, D.C., nonprofit, ranked the climate impact of various meats. Lamb was the worst offender: for every one kilogram (or 2.2 pounds) consumed, the EWG estimates that 86.6 pounds of greenhouse gases are produced. Beef was next, at 59.5 pounds of greenhouse gases. Then pork, at about 26.5 pounds. Chicken, at 15.4 pounds, is the most climate-efficient farmed meat. Meat is equally disproportionate in its thirst for water. Beans and lentils require five gallons of water per gram of protein produced, chicken nine gallons, and beef 29.6. Reductions in meat consumption can deliver outsize benefits to anyone trying to eat more sustainably. “The question isn’t beef or no beef,” says Tyedmers, who eats it about five times a year. “It’s the right quantities of it. There are grasslands on the planet that can support beef, but we need to focus on portions and frequency.” The average American currently packs away a staggering 185 pounds of meat a year, the equivalent of more than eight ounces a day. Yet the USDA’s 2010 dietary guidelines recommend just 3.7 ounces of meat per day—about a palm-size burger—which comes out to around 84 pounds per year. Eating the recommended amount would mean a 55 percent cut in meat consumption. Here’s a sense of what the planet might reap in return. A 2015 study conducted by the journal Frontiers in Nutrition concluded that a diet that is vegetarian five days a week and includes meat just two days a week would reduce greenhouse-gas emissions and water and land use by about 45 percent. Does eating grass-fed, free-range meat let you off the hook? Not really, because meat takes a toll no matter how it’s raised. Studies actually show that a factory-farm animal emits fewer greenhouse gases than a free-range one, because it lives a shorter life. But Greg Fogel, a senior policy specialist at the
