Food supplies are shrinking alarmingly around the globe, plunging the world into its greatest crisis for more than 30 years.
New figures show that this year's harvest will fail to produce enough to feed everyone on Earth, for the sixth time in the past seven years. Humanity has so far managed thanks to stockpiles built up in better times - but these have now fallen below the danger level.
Food prices have already started to rise as a result, and threaten to soar out of reach of many of the 4.2 billion people who live in the world's most vulnerable countries. And the new "green" drive to get cars to run on biofuels threatens to make food even scarcer and more expensive.
The UN's Food and Agriculture Organisation (FAO) and the US Department of Agriculture (USDA), which produce the world's two main forecasts of the global crop production, both estimate that this year's grain harvest will fall for the second successive year.
The FAO is still compiling its latest crop forecast - due to be published next month - but told the Independent on Sunday last week that it looked like barely exceeding 2 billion tons (2.03 billion tonnes), down from 2.38 billion last year, and 2.68 billion in 2004, although the world's appetite has continued to grow as its population rises.
The USDA estimates it will be even lower - 1.984 billion tons. This would mean that it would fall 58 million tonnes short of what the world's people are expected to consume this year. Ten years ago, by contrast, farmers grew 64 million tonnes more than was consumed.
The world's food stocks have shrunk from enough to feed the world for 116 days in 1999 to a predicted 57 days at the end of this season, well below the official safety level. Prices have already risen by up to 20 per cent this year.
The gathering crisis has been largely unnoticed because, for once, the harvests have failed in rich countries such as the US and Australia, which export food, rather than in the world's hungriest ones. So it has not immediately resulted in mass starvation in Africa or Asia.
Instead, it will have a delayed effect as poor people become increasingly unable to afford expensive food and find that there is not enough in store to help them when their own crops fail.
The lack of world attention contrasts with the last great food crisis, in the mid-1970s. Then Henry Kissinger - at the height of his powers as Richard Nixon's Secretary of State - called a World Food Conference, in which governments solemnly resolved that never again would they allow humanity to run short of sustenance. The conference, in Rome, resolved to eradicate hunger by the mid-1980s.
Yet, a generation later, more than 800 million people worldwide are still constantly hungry. Every day, some 16,000 young children die, at least partly because they do not get enough food. And the new food crisis threatens to be even worse than the last one. In the seven years running up to the Rome conference, grain production fell below consumption only three times, compared to six now.
It was at the conference that I first met Lester Brown, who has, ever since, been the principal prophet of the coming scarcity, repeatedly warning of the new crisis which is now upon us.
Brown - who now heads the Earth Policy Institute, a respected Washington-based think tank - gleaned his first insights into the world's predicament as a tomato tycoon when he was a teenager. Back in the early 1950s, when he was just 14, he and his brother bought an old tractor for US$200, rented a couple of fields near their home in southern New Jersey and started growing tomatoes after school.
Soon the brothers were among the top 1 per cent of tomato growers in the United States. They easily qualified for the Ten-Ton Tomato Club - "the Phi Beta Kappa of tomato growers" - which is open to those who harvested that amount per acre.
Then Campbell's Soups, trying to lower costs, threw money into research to increase yields. Within a few years, the club had to change its name to the Twenty-Ton Tomato Club. But the pace of improvement could not be sustained. Despite decades of more research, growth of yields slowed dramatically; by the mid-1990s the best growers were getting about 30 tons of tomatoes per acre.
That, says Brown, is what has been happening to the world's harvests as a whole. Between 1950 and 1990 grain yields more than doubled, but they have grown much more slowly since. Production rose from around 630 million tons to 1.78 billion tons, but has only edged up in the past 15 years, to around 2 billion tons.
"The near-tripling of the harvest by the world's farmers was a remarkable performance," says Brown. "In a single generation they increased grain production by twice as much as had been achieved during the preceding 11,000 years, since agriculture began. But now the world has suffered a dramatic loss of momentum."
Apart from increasing yields, there has always been one other way of boosting production - putting more land under the plough. But this, too, has been running into the buffers. As population grows and farmland is used for building roads and cities, or becomes exhausted by overuse, the amount available for each person on Earth has fallen by more than half.
There are more than five people on Earth today for every two living in the middle of the last century. Yet enough is produced worldwide to feed everyone well, if it is evenly distributed.
It is not just that people in rich countries eat too much, and those in poor ones eat too little. Enormous quantities of the world's increasingly scarce grain now goes to feed cows - and, indirectly, cars.
The cows are longstanding targets of Brown's, who founded the prestigious Worldwatch Institute immediately after the 1974 conference, partly to draw attention to the precariousness of food supplies. As people become better-off, they eat more meat, the animals that are slaughtered often being fed on grain. It takes 14kg of grain to produce 2kg of beef, and 8kg of grain for 2kg of pork. More than a third of the world's harvest goes to fatten animals in this way.
Cars are a new concern, with the present drive for green fuels to fight global warming. A "corn rush" has erupted in the US, using the crop to produce the biofuel, ethanol - strongly supported by subsidies from the Bush Administration to divert criticism of its failure to ratify the Kyoto Protocol.
Just a single fill of ethanol for a four-wheel-drive SUV, says Brown, uses enough grain to feed one person for an entire year. This year the amount of US corn going to make the fuel will equal what it sells abroad; traditionally its exports have helped feed 100 - mostly poor - countries.
From next year, the amount used to run American cars will exceed exports, and soon it is likely to reduce what is available to help feed poor people overseas. The number of ethanol plants built or planned in the corn-belt state of Iowa will use virtually all the state's crop.
This will not only cut food supplies, but drive up the processing of grain, making hungry people compete with the owners of gas-guzzlers. Already spending 70 per cent of their meagre incomes on food, they simply cannot afford to do so.
Brown expects the food crisis to get much worse as more and more land becomes exhausted, soil erodes, water becomes scarcer, and global warming cuts harvests.
Making cars more fuel-efficient, and eating less meat would help, but the only long-term solution is to enable poor countries - and especially their poorest people - to grow more food. And the best way to do that, studies show, is to encourage small farmers to grow crops in environmentally friendly ways. Research at Essex University shows that this can double yields.
But the world needs a new sense of urgency. "We are living very close to the edge," says Brown. "History judges leaders by whether they respond to great issues. For our generation, the issue may well be food security."