Never mind the economic crisis. Focus for a moment on a more urgent threat: the great food recession that is sweeping the world faster than the credit crunch. You have probably seen the figures by now: the price of rice has risen by three-quarters over the past year, that of wheat by 130%. There are food crises in 37 countries. One hundred million people, according to the World Bank, could be pushed into deeper poverty by the high prices.
But I bet that you have missed the most telling statistic. At 2.1bn tonnes, the global grain harvest broke all records last year - it beat the previous year's by almost 5%. The crisis, in other words, has begun before world food supplies are hit by climate change. If hunger can strike now, what will happen if harvests decline?
There is plenty of food. It is just not reaching human stomachs. Of the 2.13bn tonnes likely to be consumed this year, only 1.01bn, according to the United Nation's Food and Agriculture Organisation, will feed people.
I am sorely tempted to write another column about biofuels. From this morning all sellers of transport fuel in the United Kingdom will be obliged to mix it with ethanol or biodiesel made from crops. The World Bank points out that "the grain required to fill the tank of a sports utility vehicle with ethanol ... could feed one person for a year". This year global stockpiles of cereals will decline by around 53m tonnes; this gives you a rough idea of the size of the hunger gap. The production of biofuels will consume almost 100m tonnes, which suggests that they are directly responsible for the current crisis.
On these pages yesterday Ruth Kelly, the secretary of state for transport, promised that "if we need to adjust policy in the light of new evidence, we will". What new evidence does she require? In the midst of a global humanitarian crisis, we have just become legally obliged to use food as fuel. It is a crime against humanity, in which every driver in this country has been forced to participate.
But I have been saying this for four years, and I am boring myself. Of course we must demand that our governments scrap the rules that turn grain into the fastest food of all. But there is a bigger reason for global hunger, which is attracting less attention only because it has been there for longer. While 100m tonnes of food will be diverted this year to feed cars, 760m tonnes will be snatched from the mouths of humans to feed animals - which could cover the global food deficit 14 times. If you care about hunger, eat less meat.
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 United States. We 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 kilogram of flesh they produce; a kilogram of chicken needs just 2kg of feed. Even so, our 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? Fairlie 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 we reduced our 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.
But I cannot advocate a diet that I am incapable of following. I tried it for about 18 months, lost two stone, went as white as bone and felt that I was losing my mind. I know a few healthy-looking vegans, and I admire them immensely. But after almost every talk that I give, I am pestered by swarms of vegans demanding that I adopt their lifestyle. I cannot help noticing that in most cases their skin has turned a fascinating pearl grey.
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. These extra people will require another 325m tonnes of grain. Let us assume, perhaps generously, that politicians such as Ruth Kelly are able to "adjust policy in the light of new evidence" and stop turning food into fuel. Let us pretend that improvements in plant breeding can keep pace with the deficits caused by climate change. 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.
This estimate is complicated by several factors. If we eat less meat we must eat more plant protein, which means taking more land away from animals. On the other hand, some livestock is raised on pasture, so it doesn't contribute to the grain deficit. Simon Fairlie estimates that if animals were kept only on land that is unsuitable for arable farming, and given scraps and waste from food processing, the world could produce between a third and two-thirds of its current milk and meat supply. But this system then runs into a different problem. 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 - as most societies have done until recently - 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 the price of food barely registers. Our shops are better stocked than ever before. We perceive the global food crisis 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.
© Guardian News and Media Limited 2008