While meat consumption is booming in Asia and Latin America, in the UK it has scarcely changed since the government started gathering data in 1974. At just over 1kg per person per week, it’s still about 40% above the global average, though less than half the amount consumed in the US. Britons eat less beef and more chicken than we did 30 years ago, which means a smaller total impact. Beef cattle eat about 8kg of grain or meal for every kg of flesh they produce; a kg of chicken needs just 2kg of feed. Even so, the UK’s consumption rate is plainly unsustainable.

In his magazine The Land, Simon Fairlie has updated the figures produced 30 years ago in Kenneth Mellanby’s book Can Britain Feed Itself? Mellanby found that a vegan diet produced by means of conventional agriculture would require only 3m hectares of arable land (around half Britain’s current total). Even if the UK reduced its consumption of meat by half, a mixed farming system would need 4.4m hectares of arable fields and 6.4 million hectares of pasture. A vegan Britain could make a massive contribution to global food stocks.

What level of meat-eating would be sustainable? One approach is to work out how great a cut would be needed to accommodate the growth in human numbers. The UN expects the population to rise to 9 billion by 2050. We would need to find an extra 225m tonnes of grain. This leaves 531m tonnes for livestock production, which suggests a sustainable consumption level for meat and milk some 30% below the current world rate. This means 420g of meat per person per week, or about 40% of the UK’s average consumption.The Food and Agriculture Organisation calculates that animal keeping is responsible for 18% of greenhouse gas emissions. The environmental impacts are especially grave in places where livestock graze freely. The only reasonable answer to the question of how much meat we should eat is as little as possible. Let’s reserve it for special occasions.

For both environmental and humanitarian reasons, beef is out. Pigs and chickens feed more efficiently, but unless they are free range you encounter another ethical issue: the monstrous conditions in which they are kept. I would like to encourage people to start eating tilapia instead of meat. This is a freshwater fish that can be raised entirely on vegetable matter and has the best conversion efficiency — about 1.6kg of feed for 1kg of meat — of any farmed animal. Until meat can be grown in flasks, this is about as close as we are likely to come to sustainable flesh-eating.

Re-reading this article, I see that there is something surreal about it. While half the world wonders whether it will eat at all, I am pondering which of our endless choices we should take. Here in the UK the price of food barely registers. Shops are better stocked than ever before. The global food crisis is perceived only dimly, if at all. It is hard to understand how two such different food economies could occupy the same planet, until you realise that they feed off each other. — The Guardian