According to the study, published Monday in Proceedings of the National Academy of Sciences, a prominent scientific journal, beef production releases five times the amount of greenhouse gas emissions as the average of other meats and animal products. Nor is that all: Beef requires 28 times more land, 11 times more water, and six times as much reactive nitrogen as the average of the other categories, according to the study.
To calculate the impact of different animal products, the study's authors looked at the environmental effects of producing feed for animals, taking into account land use, water consumption and the potential for nitrogen pollution from fertilizers. (When excess nitrogen leaches into a body of water, it can cause algal blooms that deplete local levels of oxygen and cause harm to other marine organisms.) The researchers also calculated the amount of greenhouse gas given off by the animals themselves, including methane from manure. Ultimately, for each meat or animal product, the researchers were able to determine the amount of resources used to produce one calorie of that product.
When asked about the easiest and most effective way to make one's diet more sustainable, Gidon Eshel, a research professor at the Bard Center for Environmental Policy and the study's lead author, told The Huffington Post: "Really, there's no question about it. Reduce beef whenever possible."
Past research has shown that meat production contributes to global warming at a much higher rate than the cultivation of grains and vegetables. A recent study in the U.K. analyzed the diets of 55,000 people and found that the meat-eaters had twice the carbon footprint of the vegans. But if you're not ready to give up meat entirely, Eshel's study shows that you can have a big impact by just forgoing beef.
The no-beef lifestyle has its high-profile proponents. Earlier this month, business mogul Richard Branson wrote a blog post about his decision to cut beef out of his diet, noting that it was surprisingly easy to accomplish and has made him feel healthier. "I never feel like I'm missing out on anything," Branson wrote.
Eshel told HuffPost that despite a wealth of research into the benefits of a plant-based diet, "people seem unfazed by that in their consumption." Actually, though, meat consumption, and beef consumption in particular, have been on the decline in the United States in recent years. The USDA is projecting that this year, consumption of beef will be the lowest per capita since the 1950s. Whether that's because of rising meat costs, health considerations or growing pro-environment sentiment is difficult to say.
Eshel told HuffPost that maintaining an environmentally friendly diet is harder than marketers often make it seem.
"I really appreciate the good intentions of many individuals who strive in their personal choices to lessen their environmental impact," he said. "I would just caution ... against adhering to canned solutions that are purported to make matters better with little or no evidence that they in fact do."
Just because the meat in your meal is "grass-fed" or "local" doesn't necessarily mean it's good for the planet, said Eshel. More important are details like: Where was the animal raised? What was the climate of that area? What were the specific farming methods used? Someimes, Esehl said, "grass-feeding" can be even worse for the environment than the traditional corn-fed approach.
If the idea of swearing off meat turns your stomach, you can try the "vegan till 6" plan favored by New York Times food writer Mark Bittman. Or you can experiment with the popular Meatless Mondays. One thing's for sure: With animal agriculture responsible for about one-fifth of all greenhouse gas emissions worldwide, there's a lot of room for improvement.