Vegetarianism is heavily promoted. But let's say all people on Earth stop eating animal products. Can we grow enough crops so all people on the Earth are provided with enough healthy, nutritious food?

The question is of course very theoretical, but without discussing future possibilities to cultivate deserts and oceans, is there enough space to grow enough crops?

  • In accordance with Jevons Paradox the efficient production of food leads to greater overall consumption of food. An abundance of food enables population to grow, which in turn makes food less abundant. Also, consider that the power of ruling classes historically arises from an ability to control the distribution of food (and in modern times, energy). That is to say, power grows from the credible threat to withdraw the means of survival.
    – user1838
    Commented Apr 13, 2011 at 19:48
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    @bmcnett: if Jevons Paradox would apply to food, then USA would have to have population of at least 500 mln by now.
    – vartec
    Commented Jan 17, 2012 at 16:18
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    I'm not at all convinced that Jevons paradox applies. That would suggest that scarcity of grains/fruit/vegetables is the primary constraint on human population growth. I'm not ruling that out, but I would like to see some evidence before I believed that.
    – Oddthinking
    Commented Apr 6, 2012 at 1:19
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    @Oddthinking It should be self evident that the paradox applies when lack of food is the limiting factor. The situation in the developed world right now is different...growth is limited by restricted immigration and a set of cultural norms that generate sub-replacement birth rates. Commented Apr 6, 2012 at 1:41
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    Are you making an unstated assumption that we can't grow enough crops for everyone if we don't abandon the eating of meat?
    – Golden Cuy
    Commented Mar 4, 2013 at 1:42

4 Answers 4


The production of meat is much less efficient than the production of the crops the animals eat. If you would use all the grain to feed people directly instead of producting meat, it has been estimated that the US could feed about 800 million people with that grain.

One paper about "Sustainability of meat-based and plant-based diets and the environment" states that

For every 1 kg of high-quality animal protein produced, livestock are fed about 6 kg of plant protein.

The production of meat is clearly less efficient than directly producing and eating plants.

So it would be much easier to feed the world population on a vegetarian diet than with a meat-rich diet.

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    I have heard say the exact opposite. In fact, cattle can process grain much more efficiently than we can, and they can process other resources that humans cannot use at all. Using meat as an intermediary may be inefficient but the detour actually makes more energy resources available to humans than we would otherwise have. Unfortunately I don’t have a good source for this (otherwise I’d post this as an answer) but I find this answer implausible and I’m not convinced by a non peer-reviewed press release. Commented Mar 9, 2011 at 10:06
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    Cows may be able to process grain more efficiently than humans, but even if that were the case it's a two step process - cows process (eat) the grain and we process (eat) the cows. The combination of the two processes is much less efficient than eating the grain. Commented Mar 9, 2011 at 15:48
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    @Konrad The press release is about a peer reveiwed scientific paper. A link to another paper with very similar content and by the same author is here: ajcn.org/content/78/3/660S.full Commented Mar 9, 2011 at 15:53
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    @vartec The question was whether it was possible, not whether you personally would enjoy it. You may not approve of vegetarians, but they live full healthy lives. Commented Mar 20, 2012 at 13:10
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    The answer isn't saying that we need to live only on grains. It isn't even claiming that we need to abolish meat. It just states that by substituting grains (and other plants) for meat we can easily increase the amount of food available so that we can feed everyone. Commented Mar 21, 2012 at 19:38

The question is invalid, as we already produce way more than enough food. There is no more "world hunger" problem due insufficient food production. Currently much greater problem is an epidemic of obesity.

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The lowest calorie intake is in sub-Saharan Africa, where on average people eat 2,176 calories per person per day. Highest in US with a average of 3,654 calories. World average is 2800 calories. (source: "EarthTrends: Nutrition: Calorie supply per capita". World Resources Institute.).

Healthy calorie intakes is defined as between 2000 and 2500, USDA recommends 2000 calories. Thus even in most "hunger stricken" zones of the world, people eat on average more than USDA recommendation. World average is way above upper limit of healthy diet.

Of course these are averages, the problem isn't production, it's distribution of goods. In the most obese nation of the world, where food industry produces about 4,000 calories per person per day, there are 30 mln people experiencing hunger and few thousands who die annually of malnutrition (source: LiveStrong). Clearly, no one in right mind would argue, that there isn't enough food in US.

You also have to take in account, that significant progress has been made in last decades. According to Global Burden of Diseases, Injuries, and Risk Factors Study, in metric of increased risk of death, child malnutrition has dropped from 6th position in 1990 to 16th in 2010, with a overall risk drop of -62%, on the other hand obesity went up from 10th position up to 6th (+60% risk increase). Currently obesity kills 3 times more people than malnutrition.

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    I've offered up some minor edits and would also suggest changing "There is no more "world hunger" problem" by adding "due to insufficient food". There are hungry, even desperately hungry people around, especially in the less developed areas of the world. Commented Mar 4, 2013 at 4:48
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    @ChrisW: still, it's distribution problem, not a question of production.
    – vartec
    Commented Jul 22, 2013 at 8:12
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    @vartec Because subsistence farming, or laboring in a commercial plantation, just means sitting in an air-conditioned tractor all day? Even first-world farmers are abnormally active imho.
    – ChrisW
    Commented Jul 22, 2013 at 16:18
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    You cited "sub-Saharan Africa". I looked at the CIA World Factbook, looked at the map and picked Mali for example: it claims, About 10% of the population is nomadic and about 80% of the labor force is engaged in farming and fishing.
    – ChrisW
    Commented Jul 22, 2013 at 16:28
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    This answer is spot on. "There is no lack of food; there is a lack of money to buy food." (A.K. Sen) Where I live we drive our cars with fuel made from food, because we are so rich and full that we can do it. Commented Mar 21, 2017 at 17:42

This question is a very contentious one as it relies upon a lot of variables that are largely poorly understood.

The first part is arable land mass. Currently animal production is focussed on either high value grazing areas or low value extensive areas. Extensive grazing areas cannot be cropped. That area of production would have to be made up by increased crop production in other areas. 56% of Australia is extensive agriculture, worldwide it is ~5,000,000,000 hectares. That is a large amount of low production land to make up for.

http://www.nature.com/nature/journal/v478/n7369/full/nature10452.html "Simply put, we can increase food availability (in terms of calories, protein and critical nutrients) by shifting crop production away from livestock feed, bioenergy crops and other non-food applications..... But even small changes in diet (for example, shifting grain-fed beef consumption to poultry, pork or pasture-fed beef) and bioenergy policy (for example, not using food crops as biofuel feedstocks) could enhance food availability and reduce the environmental impacts of agriculture."

Also, the areas quoted vary so much, because the figures are not fully understood. Cropping land is rarely cropped every year, instead rotated or rested at intervals, dependant upon crop type, soil type and amount of water/rainfall. Some countries just don't have accurate records.

The second part is feed conversion. There are methods, such as mixed enterprise systems (crops plus grazing) and of course feedlotting that use grain feeding. The feedlotting is what people refer to the most, not understanding that cattle have a much higher energy conversion rate for vegetable matter than humans (being ruminants) and are not regularly fed for their entire lives. Thus grazing remains a large part of production.

Humans also preferentially eat higher protein foods like meat (see rise in meat demands from Asia with increasing wealth). This is because it is more calorically and nutritionally dense as a food, which is linked to satiety.

The third part is grain types. Most grains that are fed to animals are what is referred to in the grains industry as "feed grains". These are generally lower quality grains that are unsuitable for human food production. Some of the grains used cannot be eaten by humans (e.g. lupins have high alkaloid levels that give both a bitter taste and become toxic when consumed regularly). Obviously the category of feed grain varies from "could be used" through to "cannot be used" for humans. This is once again a shorfall in the production required to replace meat in the diet. Remembering that feed crops are often grown where human crops cannot be grown, or not grown regularly (e.g. see wheat classes and agronomy).

These factors combine to create quite a different picture than what is normally presented in the "can we grow enough crops to replace meat eating" discussion. There would be less land available for cropping than is available for producing a mixed diet. There would be crops produced that would not be suitable for human consumption. We would also need slightly higher production or quality of crops to make up the energy conversion gap. This all makes for a large hole in the argument.


Info on ME and DE for humans: http://fao.org/DOCREP/006/Y5022E/y5022e04.htm

This paper covers come of the conversion ratios for different animals that are grain fed (Cattle 7:1, Pigs 4:1, Chicken 2:1): http://ncbi.nlm.nih.gov/pmc/articles/PMC1240832

Another reference for the protein claims: http://sciencedirect.com/science/article/pii/S0301622699000196

  • indeed the quetion does not say how much food is adequate for a human, whether it is just for our survival. and doesnt ask about fertilizer use, be it fertilizer from livestock or mineral. Commented Dec 6, 2014 at 9:44

Meat production is highly resource intensive. A non-vegetarian meal will use several times more land, water and labour to produce than its vegetarian counterpart.

To produce 1kg of Beef approx 16,000 litres of water is needed. Compare that to 130 litres of water needed to produce 1kg of lettuce. Agriculture uses 60% of all the freshwater on the planet. So water is quite a scarce resource and meat production uses a LOT of it.

For every 1kg of meat produced several kilograms of grain have to be fed to the slaughtered animal. The land used for producing those several kilograms of grain can satisfy far more vegetarian people than non-vegetarians. Meat production is causing deforestation as we have not enough land to satisfy our needs.

If these resources were diverted to vegetable and fruit production, we could be feeding many billions of people better than we are right now.

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    Welcome to Skeptics! Please provide some references to support your claims that agriculture uses 60% of all freshwater on the planter and that we could be feeding many billions of people better than now.
    – Oddthinking
    Commented Mar 4, 2013 at 1:59
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    The numbers are probably true but irrelevant: for humans, 1kg of grain doesn’t have the same caloric and nutritional value as 1kg of beef. Furthermore, livestock can be fed with plants cultivated on soil that wouldn’t be usable for human-consumable grain. Commented Mar 4, 2013 at 10:21
  • in fact we can raise lifestock on land that is unsuitable for any other form of agriculture. That's what happens in for example south America, where large herds of cattle roam semi-free, feeding on naturally occurring vegetation, and are herded together every few weeks or months when the animals to be slaughtered, sold, or bred are selected and removed from the population. Those areas are unsuitable for the intensive agriculture that would be needed to grow crops yielding close to the same yield in calories when fed to human beings.
    – jwenting
    Commented Aug 22, 2013 at 12:28
  • Insects are more efficient than cattle, and probably not as fussy as humans, either. Edible insects: Future prospects for food and feed security Commented Jan 18, 2014 at 1:40

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