If every person on Earth adopted a vegan diet – without milk, meat, honey, or any other animal-sourced foods – the greenhouse gas emissions associated with the food system in 2050 would fall by more than half compared to 2005/2007 levels. That’s one of several striking findings from an analysis of food and climate published yesterday in the 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 are also linked to health problems such as cardiovascular disease and cancer.

Previous research has suggested that healthy diets could have environmental benefits and has explored ways to encourage such dietary shifts. 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 life-cycle 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 7 percent over current levels, the researchers calculated. This is because, as a species, we would consume less greenhouse-gas-intensive red meat and more low-greenhouse-gas fruits and vegetables, 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.

Those emissions savings would be worth $234 billion US per year in the healthy diet scenario, $511 billion for the vegetarian diet, and $570 billion for the vegan diet.

The savings in health costs from these dietary changes are even greater: $735 billion US per year in the case of the healthy diet, $973 billion for the vegetarian diet, and just over $1 trillion for the vegan diet.

These savings come from lower rates of coronary heart disease, stroke, type 2 diabetes, and cancer. In turn, those health improvements would result in 5.1 million fewer deaths per year worldwide in the healthy diet, 7.3 million in the vegetarian, and 8.1 million in the vegan scenarios.

The health, environmental, and economic benefits of all three of these dietary scenarios seem impressive on their face. But the task of reducing global greenhouse gas emissions enough to limit warming to 2 degrees Celsius in global average temperature – considered by many scientists a tipping point for climate disaster – is a truly massive one. Only the vegan diet scenario, in which the entire world’s population eschews animal foods altogether, puts the planet on track to accomplish this.

To be clear: a global vegan diet wouldn’t hold the planet below the 2-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.

And 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. The vegetarian and vegan scenarios would require even bigger shifts in production.

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. – Sarah DeWeerdt | 22 March 2016

Source: Springmann M. et al. “Analysis and valuation of the health and climate change cobenefits of dietary change.” Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.1523119113