What would happen if everyone went vegan?

The objection

“If the whole world went vegan, what would become of the billions of cows, pigs and chickens? You can’t release them into the wild, they’d starve. We’d be overrun, or forced to abandon them, and that’s before you get to the farmers. The vegan vision ends in its own welfare catastrophe.”

The answer

The objection pictures the world waking up vegan one morning to barns full of animals and nobody to feed them, but diets and herds change over years. Even the 2025 pathway from the UK’s Climate Change Committee, which advises the government on its carbon budgets and calls for fewer livestock, has average meat consumption falling by 25% between 2019 and 2040, and cattle and sheep numbers by 27% between 2023 and 2040 as farmers are helped to diversify and people eat less meat and dairy [1]. Farm animals are bred to meet demand, so as demand falls, fewer are bred and the numbers follow.

Would farm animals be released into the wild?

Nobody would need to release farm animals, because falling demand works through breeding: farmers would keep sending animals to slaughter and breed fewer to replace them. In 2024 the world slaughtered about 86 billion cattle, pigs, sheep, goats, chickens, turkeys and ducks for meat, on figures from the UN’s Food and Agriculture Organization (FAO) [2]. During a gradual shift the animals already on farms would mostly be slaughtered as they are now, and what changes is how many are bred to follow them. That is why far fewer farm animals would exist if people stopped eating them. Farm breeds would dwindle as well, though eating meat isn’t saving them now.

How quickly would the number of farm animals fall?

Chicken numbers could follow demand within months, while herds of cattle and sheep would take years to shrink. Of the 86 billion land animals in the FAO’s slaughter figures for 2024, 91% were chickens [2]. In the EU, where about 6 billion are reared for meat each year, most are slaughtered between 28 and 42 days old, and slower-growing and organic birds are kept to about 12 weeks on average, according to the EU’s food safety agency EFSA (2023) [3]. An unreplaced flock of fast-growing birds would typically be gone within six weeks and a slower-growing one after about three months, though the parent birds whose eggs they hatch from are kept for a production cycle of about 64 weeks [3]. Cattle and sheep live longer and would decline more slowly, as they have before: UK cattle and sheep numbers fell by just over a quarter between 1990 and 2010, largely in response to reforms of the EU’s Common Agricultural Policy, the Climate Change Committee notes (2025) [1].

What else would change if everyone went vegan?

The world would need about three-quarters less farmland, and food’s greenhouse gas emissions would roughly halve, according to Poore and Nemecek’s analysis (2018) of data from about 38,700 farms in 119 countries [4]. In their model a diet with no animal products cut food’s land use by 3.1 billion hectares, or 76%, and its emissions by 6.6 billion tonnes of CO2-equivalent a year, or 49%, for a 2010 reference year [4]. How much land that frees, and what it could become, is covered in what would happen to the farmland if everyone went vegan.

Feeding the world would also get easier. The crops already grown could feed the 9.7 billion people expected in 2050, Berners-Lee and colleagues found (2018), if most meat and dairy gave way to plant foods, people ate more of the crops now fed to animals, maize especially, and very large changes in many people’s circumstances gave them access to food [5]. They found no nutritional case for feeding animals crops that people could eat, and staying on today’s dietary path would need 119% more edible crops by 2050 [5]. The evidence is set out in whether a plant-based diet could feed the world.

What would happen to the people who farm animals?

Livestock jobs would shrink, and the research on what would take their place is thin. A 2026 scoping review by Nordhagen and colleagues, covering 45 studies of plant-based, cultivated, algal and insect alternatives to animal foods, found that shifts towards plant-based foods might have small net effects on employment, creating work for legume growers while cutting jobs in the livestock sector [6]. Livestock support the livelihoods of at least 1.3 billion people worldwide, according to the FAO (2025) [7], yet the review found gaps in the evidence on job numbers, incomes and job quality, and few studies from low- and middle-income countries [6]. The UK’s Climate Change Committee (2025) says farmers will need support to diversify their incomes away from livestock [1], and the review’s authors conclude that considerably more research is needed to plan a just transition for the people whose livelihoods are affected [6].