What would happen if everyone went vegan?

For scientists, policymakers and economists, the idea of a vegan future is especially interesting – and one of the biggest reasons is the environment.

Going green?

Your fridge might seem an unlikely setting for the fight against global warming, but did you know that food is responsible for over one quarter of all greenhouse gas emissions? What’s more, meat and dairy make up the vast majority of that carbon footprint.

The UN says that farmed livestock accounts for 14.5% of all manmade greenhouse gas emissions (with cow burps a surprisingly big culprit). To put that into perspective, the BBC reported that this is roughly equivalent to the exhaust emissions of every car, train, ship and aircraft on the planet.

If we all went vegan, the world’s food-related emissions would drop by 70% by 2050 according to a recent report on food and climate in the journal Proceedings of National Academy of Sciences (PNAS). The study’s authors from Oxford University put the economic value of these emissions savings at around £440 billion.

Healthy living

Being vegan doesn’t necessarily mean you’re eating healthily. You can chow down on junk food – and miss out on vital nutrients – whether you eat meat or not. For example, vegan diets are naturally low in calcium, vitamin D, iron, vitamin B12, zinc and omega-3 fatty acids. If you are following a vegan diet it is important to include protein, foods such as beans, lentils, chickpeas, tofu, soya versions of milk and yogurt and peanuts are good vegan sources of protein. Nuts and seeds are also valuable and of particular note are cashew, pistachio, flaxseeds, chia seeds and pumpkin seeds. Quinoa and buckwheat are often coined pseudo-grains but are in fact seeds - quinoa is especially useful in a vegan diet because it supplies all essential amino acids

At the same time, some vegan products contain a lot of coconut oil, for example, which is high in saturated fat. That said, it’s easy to get the right food balance as a vegan, but you need to be aware of what you’re eating – good advice for omnivores and herbivores alike.

We know that Western diets are linked to many health problems including heart disease, diabetes and obesity. In 2015, the World Health Organisation went so far as to categorise processed meat as “carcinogenic”, along with asbestos, alcohol and arsenic.

With fewer cases of lower coronary heart disease, strokes, type 2 diabetes and some cancers, its researchers report that a global vegan diet would also result in 8.1 million fewer deaths per year worldwide. This would have projected cost savings of “$700–1,000 billion per year on healthcare, unpaid care and lost working days”.

Make hunger history

Would a vegan future make food poverty history? If it’s about freeing up space and resources for growing food, there’s some evidence to back that up.

A meat-eater’s diet requires 17 times more land, 14 times more water and 10 times more energy than a vegetarian’s, according to research published by The American Journal of Clinical Nutrition. This is principally because we use a large proportion of the world’s land for growing crops to feed livestock, rather than humans. (Of the world’s approximately five billion hectares of agricultural land, 68% is used for livestock.)

This squeeze on resources is only set to intensify. In 50 years’ time, the UN predicts there will be 10.5 billion people on the planet (the current world population is around 7 billion). To feed us all, it says, we will need to grow food more sustainably. Dr Walt Willett, professor of medicine at Harvard University, says we could eliminate the worst cases of world hunger today with about 40 million tonnes of food – yet 760 million tonnes is fed to animals on farms every year.

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One of the counter-arguments against this vegan solution is that some grazing land simply isn’t suitable for growing crops. That’s certainly true, but there’s actually a bigger problem with eradicating world hunger. Right now, we already produce more than 1½ times the amount of food needed to feed everyone on the planet. It just doesn’t get to everyone in need.

In other words, having enough to eat is as much about politics and big business as dietary choices – so there’s nothing to say that hunger would be a thing of the past in a vegan world.

Culture shock

It should also be remembered that we've been farming and eating livestock for around 10,000 years. Our diet isn’t just the food on our plate – it shapes everything from our jobs and trade to our religious and cultural identities. Today, the global meat and dairy industries provide work for millions of people in often very poor communities around the world.

Where would all the animals go?

If we no longer bred farm animals, what would happen? Would they go extinct? Would they overrun the planet?

Billions of farm animals would no longer be destined for our dinner plates and if we couldn’t return them to the wild, they might be slaughtered, abandoned, or taken care of in sanctuaries. Or, more realistically, farmers might slow down breeding as demand for meat falls.

Farm animals are bred far more intensively than they reproduce in the wild – so any “cows take over the world” scenarios are a little far-fetched. As with all wildlife, any returned animal numbers would fluctuate and reach a balance, depending on predators and available resources in the wild.

It’s worth noting that not all animals could simply “go free”. Some farm breeds, such as broiler chickens, are now so far removed from their ancestors that they couldn’t survive in the wild. Others, like pigs and sheep, could feasibly return to woodlands and grazing pastures and find their own natural population levels. On top of that, even if we stopped eating animals, our destruction of wild habitats would still reduce their numbers. With nature, it’s always a question of balance.

Paul Allen is author of The Ethical Careers Guide and founder of tone of voice agency Lark

For more on vegan diets, we've collaborated with BBC Future – read the BBC Future guide to the health benefits of going vegan.