But these idiocies, Fairlie shows, are not arguments against all meat eating, but arguments against the current farming model. He demonstrates that we've been using the wrong comparison to judge the efficiency of meat production. Instead of citing a simple conversion rate of feed into meat, we should be comparing the amount of land required to grow meat with the land needed to grow plant products of the same nutritional value to humans. The results are radically different.
If pigs are fed on residues and waste, and cattle on straw, stovers and grass from fallows and rangelands – food for which humans don't compete – meat becomes a very efficient means of food production. Even though it is tilted by the profligate use of grain in rich countries, the global average conversion ratio of useful plant food to useful meat is not the 5:1 or 10:1 cited by almost everyone, but less than 2:1. If we stopped feeding edible grain to animals, we could still produce around half the current global meat supply with no loss to human nutrition: in fact it's a significant net gain.
It's the second half – the stuffing of animals with grain to boost meat and milk consumption, mostly in the rich world – which reduces the total food supply. Cut this portion out and you would create an increase in available food which could support 1.3 billion people. Fairlie argues we could afford to use a small amount of grain for feeding livestock, allowing animals to mop up grain surpluses in good years and slaughtering them in lean ones. This would allow us to consume a bit more than half the world's current volume of animal products, which means a good deal less than in the average western diet.