If every person on Earth adopted a vegan diet—one without milk, meat, honey, or any other animal products—the greenhouse gas emissions associated with the food system in 2050 would fall by more than half compared to baseline levels in the early 2000s. That’s one of several striking findings from an analysis of food and climate published in Proceedings of the National Academy of Sciences.
The food we eat is responsible for over one-quarter of global greenhouse gas emissions. Of those, 80 percent are linked to livestock production. Eating too much red meat and not enough fruits and vegetables is also linked to health problems such as cardiovascular disease and cancer.
Previous research has suggested that healthy diets could have environmental benefits. But the new study is the first to quantify the health, environmental, and economic benefits of dietary changes all at the same time.
To do this, researchers from the University of Oxford in the UK combed through reams of data from the UN Food and Agriculture Association, the World Health Organization, and previous epidemiological and lifecycle-analysis studies to compare the effects of various approaches to eating.
If current dietary habits and trends continue, the greenhouse gas emissions associated with the food system in 2050 will be 51 percent higher than current levels. This is due to factors including global population growth and the fact that as populations get wealthier, they tend to start eating more meat.
But if everyone in the world followed international dietary guidelines for healthy eating, 2050 emissions from the food system would be held to just seven percent over current levels, the researchers calculated. This is because, as a species, we would consume less greenhouse gas–intensive red meat and more fruits and vegetables low in greenhouse gases, as well as fewer calories overall.
Similarly, the researchers calculated that if everyone ate a vegetarian diet, consuming eggs and dairy but no meat, emissions would fall by 44 percent. Emissions would decrease by 55 percent if everyone became vegan.
The cost savings are also impressive: for the healthy diet scenario, they amount to $234 billion US per year in emissions savings and $735 billion US per year saved in health costs. It only goes up from there.
The health, environmental, and economic benefits of all three of these dietary scenarios seem impressive on their face. Only the vegan diet scenario, however, puts the planet on track to limit global warming to two degrees Celsius, considered by many scientists a tipping point for climate disaster.
To be clear: a global vegan diet wouldn’t hold the planet below the two-degree threshold on its own; it would merely enable the food system to make its proportional contribution to this task. This means that if we want to keep eating animal products, we’ll have to find extra emissions savings elsewhere.
Any of these alternative diets would involve huge shifts in the global food system. In the healthy global diet scenario, the world’s agricultural system would need to produce 25 percent more fruit and vegetables, and 56 percent less red meat, than it does today.
Still, it’s worth considering eating more lentils. The researchers calculated that three-quarters of the environmental and health benefits from changing diets would occur in developing countries. But developed countries would gain most per capita. So particularly for people who live in wealthier countries, changing one’s diet could be a meaningful climate action indeed.