The difference found in diet-driven carbon footprints was significant. Halve your meat intake, and you could cut your carbon footprint by more than 35 percent; stick to fish, and you could cut it by nearer to 50 percent; go vegan, and the difference could be 60%.
The variations were so drastic that the study's authors suggested that countries should consider revising their definition of a sustainable diet. "National governments that are considering an update of dietary recommendations in order to define a ‘healthy, sustainable diet’ must incorporate the recommendation to lower the consumption of animal-based products," the study says.
The good news is that while Americans might still eat more meat than mother nature would prefer, they are scaling back, and especially so with the most environmentally unfriendly kind—per capita beef consumption has fallen by 36 percent since its peak in 1976, according to data from the USDA. The bad news is that the rest of the world appears to be headed in the opposite direction. Global demand for meat is expected to grow by more than 70 percent by 2050, largely driven by burgeoning middle classes in the developing world. Couple that with the potential for changing health narratives in the U.S.—some of which now tout red meat (and fats, in general) as healthier than once thought—and even Americans could find themselves putting more meat on their plates in the future.