Each year around this time, farmers across the breadbaskets of the Northern Hemisphere hop on their tractors and drive out to their fields, full of hope for the new season's grain crop. For the past four years, their efforts haven't been too successful.
It has been an almost unprecedented run of misfortune: four back-to-back meagre harvests, as heat waves, drought and pestilence took their toll -- something that hasn't happened since at least 1960.
As a result, since the turn of the millennium, the amount of grain held in the world's stockpiles has been falling. At the end of the 2003 harvest, the amount of wheat, corn, rice and other grains had fallen to about 280 million tonnes. In 1999, it was more than 500 million.
That seems like a lot of grain because bakers can make about 2,000 loaves for every tonne of wheat milled into flour. But considering that the grain has to support both the world's human population and its billions of livestock, there is precious little to go around.
Measured against consumption, there is enough grain left in the planetary larder to last for only 59 days, one of the lower figures on record. After it is used up, people will go hungry if the next harvest fails.
The string of bad harvests hasn't attracted widespread attention yet, but it has the almost undivided attention of Lester Brown, one of the more thoughtful -- and controversial -- environmentalists in the United States. The founder of the influential Worldwatch Institute, a think tank based in Washington, D.C., believes that the line of bad harvests is no fluke of nature, but rather a harbinger of what one writer has termed "gastronomical Armageddon" -- a chaotic and protracted period of food shortages triggered by the world's environmental plagues, including global warming and water shortages.
Environmentalists have long fretted about such things as clear-cutting, species extinction, rain-forest destruction and melting ice caps. But, as important as these issues may be, Mr. Brown thinks that the biggest flashpoint for environment problems is on the world's farms.
The shrinkage of the food supply will be where environmental degradation will have a huge impact on people, he says. "Rising food prices may be the first global economic indicator to signal serious trouble in the relationship between us and the Earth's natural systems and resources," he says.
Mr. Brown thinks that some sort of food crisis is almost inevitable because the magnitude of the exhaustion of grain stockpiles has been staggering. It's equal to about five years of the entire grain output of Canada, one of the top agricultural exporters.
The harvest shortfalls have become so immense, he says, it would take superlative crops in prime agricultural regions this year and next to even begin to start refilling the larder. "I think the chances of farmers digging their way out of this hole are less than one in 10."
Mr. Brown believes that three main environmental trends are threatening to show up, like an unwelcome guest, at humanity's dinner table: global warming, water shortages in many parts of the world and farmland degradation in China.
He details his case in his latest book, Plan B, Rescuing a Planet Under Stress and a Civilization in Trouble.
Not everyone buys Mr. Brown's foreboding projections, of course. He has been criticized, usually by conservatives, for being a modern Malthusian, a reference to 19th-century British economist Thomas Malthus. Malthus believed that humans faced imminent famine about 200 years ago because population growth would outstrip the agricultural capacity of the land. His prediction didn't come to pass -- at least not yet -- because rising agricultural yields have always outpaced population growth.
The United Nations Food and Agriculture Organization is optimistic that grain stockpiles can be rebuilt from their current nadir. In a forecast issued last month, the Rome-based FAO said it expects an above-average harvest this year "that could help alleviate the tight global supply situation."
Yet Mr. Brown's ideas are making waves among environmentalists and others.
In the United States, media magnate Ted Turner came upon his new book and thought its worrisome content was so persuasive that he bought more than 3,000 copies for distribution to people he knows. Mr. Brown has been on a busy lecture circuit since the book's publication last year, making the case for imminent food shortages to large audiences.
Global warming could be such a threat to food supplies because of the pernicious impact that searing summer temperatures have on the ability of plants to fertilize their seeds, cutting crop yields. Although it is scary to contemplate, new research shows that it wouldn't take much warming from current summer high temperatures to cause almost complete crop failures.
The research, based on tests in the tropics where hot weather is common, shows that as temperatures rise above 30 degrees when plants flower, the yields of rice, wheat and corn -- the staples of the human diet -- begin to fall. Although it doesn't work exactly the same way for all crops, there is a drop of about 10 per cent in yield for every one-degree increase.
Readings above 30 degrees amount to a hot summer day in most areas of southern Canada, and are experienced only occasionally. But the same could have been said of Europe -- until last year. Much of Europe's grain belt had a sneak preview of what warming can do as temperatures soared above the thermal optimum for plant growth over wide areas.
"Those off-the-chart temperatures in Europe, the ones that took 35,000 lives in nine countries, those temperatures shrunk harvests in every country from France east to Ukraine," Mr. Brown says.
His thinking has also been influenced by a refinement of the temperature research that has been conducted at the International Rice Research Institute in the Philippines. Scientists there have found that the fertilization of rice seeds falls from 100 per cent at 34 degrees to near zero at 40 degrees.
Rising temperatures may be one reason that world grain harvests have either fallen, or stagnated for the past eight years.
After temperatures, water is a second crucial element for successful plant growth.
Many countries, including the United States, India and China, irrigate using groundwater and are pumping unsustainable amounts to quench the thirst of their crops. The result is depleting aquifers, and eventually, an agricultural system that will be short of water when the resource is mined out. In North America, the big worry is over water levels in the once mighty Ogallala aquifer under the U.S. Great Plains, the world's bread basket.
"When you realize that more than half the world's people live in countries where water tables are already falling, you can begin to see how literally explosive this water issue can be," Mr. Brown says.
Droughts have also emerged as a big problem. Canada's Prairies has been exceedingly dry for years. In 2002, high temperatures and lack of rain hit India, the United States and Canada simultaneously. Last year, it was Europe's turn in the rotisserie.
The other big influence on global food supplies has been China, where grain production has been in a steep fall for the past five years. The 2003 harvest was nearly 20 per cent below the 1998 crop, a shortfall of 60 million tonnes, a drop larger than Canada's entire annual grain output.
Mr. Brown attributes the Chinese decline to a number of factors. Productive agricultural land is being lost to factories and roads, for one thing, as the country undergoes its rapid industrialization. He said providing for China's new cars has alone chewed up the same amount of land as 100,000 U.S.-sized football fields.
Another problem is that Chinese deserts are expanding, in part because of overgrazing, further cutting into its agricultural land.
Mr. Brown thinks that the drop in Chinese grain production will soon cause the country to enter world food markets in a big way, driving up prices in much the same way that the Soviets did in the early 1970s when they cornered the U.S. grain supply.
Dire warnings of imminent global food shortages should be welcome news in Canada's long suffering farm belt. Years of battling poor prices, mad cows and rainless skies have cut a swath out of farm incomes. Mr. Brown's messages, as grim as they are for most of us, have a wonderful silver lining for food producers.
Yet here there is deep skepticism. Paul Beingessner, a farmer in Truax, Sask., who also writes an agricultural column for Prairie weekly newspapers, has gone to one of Mr. Brown's lectures. Afterward, he whimsically dubbed the message "gastronomical Armageddon" and developed an alternative explanation for the decline in the world's grain stocks based on what he sees at the farm gate.
Mr. Beingessner thinks that prices for grains have been low for so long that it doesn't really pay to farm any more, or at least it doesn't pay to invest in the expensive fertilizers, efficient irrigation equipment and other items that would boost crop yields.
He believes that the lack of profit in farming is the main factor driving the fall in food output. "What I'm seeing is that as returns shrink from agriculture as they have been literally for two decades, that farmers are unable to produce to the capacity of the land," he says. "I think [Mr. Brown] is wrong in a lot of ways. We are really under-producing."
If farmers were able to earn decent incomes, he says, they would respond in kind by refilling the world's granaries. "You pay farmers and they'll produce an immense amount more," he predicts.
Mr. Brown, for one, remains doubtful that his forecast food calamity can be avoided.
His book recommends that society take evasive action by having farmers begin to use water more judiciously to ration available supplies. He says emissions of carbon must be cut in half by 2015 to forestall the worst projections of global warming and that the world has to quickly rein in its growing human population.
Doing these things, in Mr. Brown's view, would be a big help to avoid the crisis he foresees. "Whether we're politically capable of doing them remains to be seen. In difficult times, you never know if you're going to have a Nero or a Churchill," he says.
Reserves as a percentage of consumption
Perhaps the clearest indicator, this measure is at a low of 16.2%