Carbon

Vegan diets have about a 75% smaller climate footprint

By WhyStopHarmingAnimals.com

A vegan diet produces about three-quarters less climate-heating gas than a diet heavy in meat[1][9]. That was the finding of a 2023 study in Nature Food by Scarborough and colleagues, which looked at the diets of about 55,000 people in the UK and worked out the environmental cost of what each of them ate[1]. Vegans came out lowest on every measure the researchers tracked. Compared with people eating 100 grams of meat a day or more, vegan diets produced about 75% less greenhouse gas[1][9], about 73% less water pollution[1] and about 75% less land use[1].

Food is a quarter of the problem

Food production accounts for about 26% of global greenhouse gas emissions, according to Our World in Data, and most of that comes from animals and their feed[2][4]. When Xu and colleagues split the global food system’s emissions in a 2021 paper in Nature Food, about 57% came from animal-based foods (including the crops grown to feed the animals) and about 29% from plant-based foods[3]. Poore and Nemecek’s 2018 meta-analysis in Science found that meat and dairy provide about 18% of the world’s calories and about 37% of its protein, yet produce about 60% of agriculture’s greenhouse gases[4]. Animal foods cause about twice the emissions of plant foods[3] while supplying far less of what people eat.

That meta-analysis, which pulled together data on food production around the world, concluded that avoiding meat and dairy is the single biggest way to cut the climate, land and water impact of what you eat, more than buying local or organic.

Where the emissions come from

To eat animals, we first have to grow plants for them. The animal then turns most of those calories into body heat, manure and methane, a gas that traps far more heat than carbon dioxide. Cows produce methane as they digest. Manure releases more greenhouse gases as it breaks down. And the feed has to be grown somewhere: about 80% of agricultural land is tied up in pasture and feed crops[5], and a lot of that land was forest before it was cleared, which released the carbon stored in the trees and soil.

A plant eaten directly skips all of those steps. There is no methane from digestion, no manure lagoon and no extra field of feed, which is why the gap between vegan and high-meat diets is so wide[1].

Buying local doesn’t close the gap

Buying local is one of the most common pieces of green advice, and for most meals it barely moves the numbers[6]. Our World in Data’s analysis of food emissions shows that what you eat, plants or animals, matters more than how far the food traveled[6]. Transport is a small slice of most foods’ footprint. The large slice comes from how the food was produced.

Raising an animal takes so many resources that the distance to the shop hardly registers[6]. A dairy cow can drink over 40 gallons of water a day, according to the University of Nebraska-Lincoln[7], and North Dakota State University’s extension service puts cows at roughly 20 to 50 gallons a day depending on heat, size and whether they are producing milk[8]. Cows can eat over 100 pounds of plant food a day, and all of it has to be grown before the animal is ever loaded onto a truck. A cow digesting grass releases methane whether the farm is in the next valley or on another continent, and the land cleared for its pasture released its carbon either way.

Plants need very little by comparison, and farm animals are fed plants anyway. Vegan food shipped from across the world is still far more efficient than an animal raised and killed locally[6]. The main exception is food flown by air freight, which carries a much larger transport footprint than food moved by ship or truck, and even there the gap between one vegetable and another is small next to the gap between plant foods and meat.

What the UK study can and can’t tell us

Scarborough’s study is observational[1]. It linked what people reported eating to environmental data for each food, so it did not measure emissions from each person’s plate, and it was carried out in one country[1]. Its headline comparison is with high-meat eaters[1], so someone who already eats less meat would see a smaller cut by switching, and the study’s other groups (lower meat eaters, fish eaters, vegetarians) fell between the two ends. Yale Environment 360’s summary of the paper reported the same ranking[9].

The global datasets back up the direction[3]. Xu’s split of the food system and Poore and Nemecek’s meta-analysis use different methods and data from the UK study, and both put animal foods at the top of the food system’s emissions[3][4]. What goes on the plate is one of the largest climate decisions most people make each day, and they can change it at the next meal.