What would happen if everyone went vegan?

What would happen if every person on Earth adopted a vegan diet – without milk, meat, honey, or any other animal-sourced food? It’s a (very) hypothetical question, but environmental writer Paul Allen argues that it's more relevant than ever.

Cows standing in a misty field

The idea of everyone adopting a vegan diet might sound extreme, but in the last decade, the number of people in the UK following a plant-based diet has risen 340%. There are now over 0.5 million British vegans – with around 20% of 16 to 24-year-olds in the UK following a vegetarian or vegan diet.

You can see this growing interest in veganism all around us. From the explosion of dairy-free milk alternatives on supermarket shelves and the growing number of celebrity advocates like Liam Hemsworth and Natalie Portman, to movies like Cowspiracy and Simon Amstell’s futuristic vegan comedy Carnage. What was recently a radical lifestyle choice is slowly moving into the mainstream.

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.

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.

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What is your opinion on this topic? We'd love to hear from you below...

For more on vegan diets, we've collaborated with BBC Future – read more below:

The health benefits of going vegan – BBC Future
Why vegan junk food might be even worse for your health – BBC Future
How a vegan diet could affect your intelligence – BBC Future
The hidden biases that drive anti-vegan hatred – BBC Future
The mystery of why there are more women vegans – BBC Future
Why the vegan diet is not always green – BBC Future
Which milk alternative should we be drinking? – BBC Future

Comments, questions and tips

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Chandan Rajah's picture
Chandan Rajah
24th Apr, 2020
I wonder what would happen with no formula milk. What will we use as an alternative. Also, what would happen to a population that suddenly doesn’t get all the required levels of vitamins and nutrients? Lots of artificial food supplements perhaps.
Kat Sutter's picture
Kat Sutter
16th Feb, 2020
Plus, what would we feed our pets? Dogs and cats (especially cats) are NOT meant to be vegans. They're carnivores. Cats are what they call "obligate carnivores". A vegan diet can be harmful, even fatal to them. (Forget all that nonsense from PETA, cats MUST have meat)
Tanuki Soba's picture
Tanuki Soba
14th Feb, 2020
A very interesting conversation, but also a very polarising one. It isn’t reasonable to expect that the whole world will “go vegan”. It is imperative that consumption of slaughtered meat be reduced though. I specify “slaughtered meat” because “cultured meat” will likely become a viable alternative. As with renewable energy, slaughtered meat alternatives will likely be diverse, from insects to veg burgers to beans. Currently we are essentially replacing wild species with farmed ones, and this practice cannot continue if biodiversity is to be preserved. https://www.theguardian.com/environment/2018/may/21/human-race-just-001-of-all-life-but-has-destroyed-over-80-of-wild-mammals-study
14th Nov, 2019
Reading the comments and the arguments of the meat eating users gives me no hope that humanity will ever change and stop meat consumption. I stopped eating meat about 3 months ago and I feel extremely healthy and happy. And knowing that my choice not only made me a healthier person but also made the world a better place makes me very happy. My advise to all meat consuming fellows is to give it a chance, try it for a week, you will feel the difference straight away. Don't do it just for the planet, do it for yourselves. I stopped eating meat mostly for selfish reasons and protecting the planet was a bonus. 90% of the world's biomass is livestock - animals that we keep alive at all times to feed ourselves. These animals are vegans building and supporting their bodies with the food which they take from plants. So eating their meat makes the animal a middle man between the plants and us - the humans. It's certainly a very easily comprehensible thing that eating plants is the healthier way to live. Food organisations just need to start focusing in finding ways to make delicious vegan recipes as at the moment the choice in variety is still very limited.
7th Oct, 2019
There is also the fact that a lot more processed food would need to be produced…man made. Plus a lot more supplements would have to be taken to ensure health for everyone: eg, vitamin B12 which CANNOT be sourced anywhere except animal products, (in case anyone comes up with a plant based idea of B12 they have to know that it is B12 analogues (and inactive) that are in plant foods and our bodies cannot use them. They also block the body's B12 receptors stopping any active B12 from being used. Cutting out full food groups from a diet will have a knock on effect somewhere. Even the Vegan society tells vegans this. Seems to me that if a person's diet cannot give that person everything that their body needs in order to regain healthy, then the diet is faulty.
Guy's picture
22nd Sep, 2019
I just don't understand the logic or rationality in this. Go vegan because cows burp, and contribute so much to climate change? That doesn't make sense. Would you also suggest we stop wearing clothes because our synthetic clothes will poison the oceans and landfill for thousands of years? Going vegan means no animal products in your life, not just no ungulates. There are plenty of sources of good healthy nutrition from animal products that do not contribute to global warming. Pigs, rabbits, fish, duck and chicken are just a few meats that can be reared sustainably without contributing to climate change. Cattle and sheep too if they are farmed correctly. This is a good argument for stopping modern methods of factory feedlot farming of cattle but this has nothing to do with whether or not we should eat meat. In fact Traditional mixed rotational farming is good for the environment. It creates a sustainable bio-diverse ecosystem, it is good for the animals, and best of all it helps reduce carbon in the atmosphere. Farms run on these lines can be carbon neutral or even carbon negative. And this would be a major source of carbon capture since we seem to have such a problem reducing burning fossil fuels, which is the overwhelming main caise of climate change. Going vegan would create even more environmental problems not to mention health problems. There is a good reason why Humans have never gravitated towards a vegan diet and there is no vegan culture anywhere in the world.
Tanuki Soba's picture
Tanuki Soba
14th Feb, 2020
Where I live, in Australia, land clearing for cattle grazing is the main driver of deforestation, and in turn biodiversity loss. 60% of this beef is exported. As you say, there are more sustainable ways to produce meat products, just as there are more sustainable ways to produce clothing. But meat consumption overall must be reduced significantly if sustainability is to be achieved. Converting native forest into meat is not viable.
27th Nov, 2019
Very valid points! Sustainability should be the solution not going towards different extremes. Crop rotation would also help in reducing food wastage and replenishing our land that has been severely drained from our poor agricultural practices. If corporate greed is what’s driving companies to adopt a stance (meat production vs meat alternative processed food), then we are lost.
26th Jul, 2019
"Do the best you can until you know better. Then when you know better, do better.” -Maya Angelou Now we know better (thanks to our extensive information sharing) let's do better. A world where sensory pleasure dictates what's right and what's wrong remains a pretty scary world.
Guy's picture
22nd Sep, 2019
Sensory pleasure has nothing to do with it, Benedict, It is all about nutritional needs and eating what the Land provides through geographical variance.


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