Is going vegan better for the environment?

The objection

“Vegan environmental claims are inflated internet memes. Modelled diets aren’t what people really eat, impacts vary from farm to farm, and the real-world effect is marginal.”

The answer

Specific numbers do get inflated online, and the objection’s best point is a real one: many studies model idealised diets that fail to reflect what people actually eat, as the authors of the most direct test say themselves (2023) [1]. That test, though, found the gap is large in real diets too.

How much lower are the emissions of a vegan diet?

A vegan diet has about a quarter of the climate impact of a diet heavy in meat. Scarborough and colleagues at Oxford (2023) linked the recorded diets of 55,504 vegans, vegetarians, fish-eaters and meat-eaters in the UK to food data from 570 life-cycle assessments covering more than 38,000 farms in 119 countries, keeping the variation in where and how food is produced [1]. Vegan diets produced 25.1% of the greenhouse gas emissions of diets with 100g or more of meat a day (95% uncertainty interval 15.1 to 37.0%), and 25.1% of the land use, 46.4% of the water use, 27.0% of the eutrophication, or nutrient pollution of water, and 34.3% of the biodiversity loss [1]. Every measure rose with the amount of animal food eaten, and even low meat-eaters differed from high meat-eaters by at least 30% on most of them [1]. The diets were recorded in the 1990s and matched to food footprints from 2019, and the volunteers were recruited partly through vegetarian magazines and societies, so they are not a random sample of the country [1].

Would a global shift to plant-based diets make a dent?

A worldwide shift would cut food’s land use by about three-quarters and its emissions by about half. Poore and Nemecek (2018) pooled data from about 38,700 farms in 119 countries covering 40 products that make up about 90% of the world’s protein and calories [2]. They found that a move to diets without animal products would cut food’s land use by 3.1 billion hectares, or 76%, and food’s greenhouse gas emissions by 6.6 billion tonnes of CO2-equivalent a year, or 49%, as well as acidification by 50%, eutrophication by 49% and scarcity-weighted freshwater use by 19% [2]. The land no longer needed could also draw down about 8.1 billion tonnes of CO2-equivalent a year over 100 years as natural vegetation returns [2]. Oxford’s own summary put the freed area at the size of the US, China, the European Union and Australia combined [3].

The reason is how much land animal foods take for what they return. Meat, farmed fish, eggs and dairy use about 83% of the world’s farmland but provide only 37% of its protein and 18% of its calories [2]. Even the lowest-impact animal products typically do more damage than the vegetable proteins that could replace them [2], which is why Oxford summarised the study as finding that avoiding meat and dairy is the single biggest way to reduce your environmental impact on the planet [3].

One person’s diet won’t visibly move these totals. “Overstated” is a claim about whether the impact has been exaggerated, though, and the size of one plate has no bearing on that.