Usually the soil has to be fertilised in some way, from dung, rocks or fossil fuels. Usually the water has to be moved from other places to make up for irregular rainfall. Sometimes the sun is not strong enough and the crops or animal feed has to come from somewhere with warmer weather, or be grown under artificial conditions. Almost always, the food has to be transported from one place to another.

In a world with a growing population, whose average calorie consumption is rising, and whose demand for more exotic food is being accelerated by advertising and globalisation, there is one other, almost invisible factor that may be making a huge difference on our global footprint : the amount of food which comes from animals.

So, just for a few minutes, I would like you to suspend any cultural, religious or habitual feelings you have about diet, and just assume that everyone on this planet suddenly became vegan. That is, nothing they consumed derived from animals.

According to the UN Food and Agricultural Organisation the typical industrialised consumer derives 28% of all of their calories from animals; largely meat and dairy products. For developing countries this goes down to 8%, so let’s strike an average of 15% for the world as a whole.

As part of a detailed and objective analysis in 2000, Vaclev Smil discovered that the use of the world’s grain harvest alone for animal fodder had gone up from just 20% in 1950 to 45% in the late 1990s, including 60% of all grain produced in the USA.

Smil also found that, if we take 1kg of vegetable matter to equal 1kg of gross energy consumed, then converting the 1kg consumed product into milk would require 4-5kg vegetable matter; pork, 5-7kg vegetable matter; chicken 7-10kg vegetable matter; and beef, 20-25kg vegetable matter.

We can see straight away that a move away from beef to chicken would provide an approximate 65% saving in the amount of vegetable matter required to produce the final food product, and even more if a switch was made away from meat entirely to dairy; effectively a lacto-vegetarian diet. At only 1kg vegetable matter to 1kg gross energy, there is a huge additional benefit, environmentally, in switching to a completely animal free diet.

In fact, with beef accounting for 25% of the global meat total; pork, 39%; and poultry, 29%; we can take an average of 11.2kg of vegetable matter required for just 1kg of food energy for the whole world.

Based on the UN FAO figures above, this means that the global average of 15% calories from animals requires twice as much vegetable matter as the 85% of non-animal calories consumed worldwide. Therefore, if we all went vegan we would need only one third of the cropland we use now.

This is a remarkable figure and one that is scarcely believable; but look at the figures, and that’s what comes out. And what also comes out is this:

Currently 80m tonnes of nitrogen fertiliser is produced worldwide every year. Because nitrogen fertiliser production generates nitrous oxide, which has a global warming potential 300 times that of carbon dioxide, the emissions from nitrogen fertiliser comes out at a massive 1376m tonnes CO2 equivalent. In other words, reducing the amount of nitrogen fertiliser by two thirds would offset over 3% of the carbon dioxide produced by humans every year.

The amount of carbon dioxide generated by food transportation in the UK in 2002 was 19 million tonnes , which does not include the distance travelled by animal feed. Calculating the amount of CO2 generated by animal feed transportation is tremendously difficult owing to the complexity of the supply chain; however, given the global nature of the animal feed market, the raw materials are unlikely to have been produced any more locally than the average UK apple, quite the converse, in fact. Therefore, we can safely say that if we include animal feed, the true emissions from UK food is closer to 60m tonnes CO2. Globally, the industrialised world therefore produces around 600m tonnes CO2 from food transportation, and the whole of the world a very approximate 1500 million tonnes. The global reduction in carbon dioxide would therefore be around 1000m tonnes, or 4% of all carbon dioxide emissions.

Deforestation is an unfortunate side-effect of cropland growth, especially when the forest being destroyed is amongst the world’s richest and most vital habitats, which absorbs around 8% of the world’s CO2 each year. Every year around 20,000 square miles (out of 7 million) of the Amazon is lost through deforestation, with over half of that caused by cattle ranching or soya production. Even though the 0.3% loss annually seems very small, the combination of cumulative loss (17% in the last few decades) and the huge amount of carbon returned to the air through burning and decomposition, is potentially catastrophic for the global environment. A one third reduction in Amazon deforestation resulting from global veganism would be a major saving grace for this irreplaceable resource.

And these are just three examples from many others, including all of the other forests destroyed for cropland; the 19% of global methane produced by farmed ruminant animals; and the run off from slurry, pesticides and fertiliser poisoning oceans and rivers worldwide.

But, even so - setting aside the cultural, religious and habitual arguments for or against it - there are bound to be objections to the hypothesis of global veganism. Some of the more likely ones are answered here:


Humans need protein and meat-based nutrients to survive.

There are plenty of vegetable-based alternatives; beans, pulses and nuts of all types, which will suffice. More specifically to veganism, vitamin B12 and other key nutrients can be synthesised, which would be a small price to pay for the environmental benefits.


Soya is destroying the Amazon.

As shown earlier there is really no need for any forest destruction given the two thirds reduction in land requirement. In fact veganism may even allow the Amazon to one day return to its natural state.


There is plenty of fish in the sea; why can’t we use this?

Unfortunately this is patently untrue. At West African rates of consumption, wild fish stocks can be maintained, but at the current global rate of fish consumption, which includes vast amounts of fish meal used for farmed fish, many of the most valuable ocean fisheries have already collapsed. An increase in consumption would destroy many of the key food chains that life depends on, forever.


There will be millions of starving people if they are not allowed to eat animals.

The average calorie consumption worldwide is 2800 per day – enough to sustain an average human. In the industrialised world this goes up to over 3300 calories. With a 30% obesity level in the USA there is no question that food inequality is rife, and even if we do have to selectively increase calorie consumption to stave off famine in the worst hit areas, why should this not be offset from the richest countries? Only politics stands in the way.


Realistically, global veganism is not going to happen; but realisation that our obsession with animal based protein and fat is causing global environmental damage on an epic scale, and that by reducing this consumption we could help reduce the greenhouse effect, must be food for thought. Even if not everyone can stomach the outcome.