The Globe and Mail's Martin Mittlestaedt on why some experts think food supply might be among the first major casualties of global warming.

An excerpt:

That's the view of a small but influential group of agricultural experts who are increasingly worried that global warming will trigger food shortages long before it causes better known but more distant threats, such as rising sea levels that flood coastal cities.

The scale of agriculture's vulnerability to global warming was highlighted late last year when the Consultative Group on International Agricultural Research (CGIAR), an umbrella organization representing 15 of the world's top crop research centres, issued an astounding estimate of the impact of climate change on a single crop, wheat, in one of the world's major breadbaskets.

Researchers using computer models to simulate the weather patterns likely to exist around 2050 found that the best wheat-growing land in the wide arc of fertile farmland stretching from Pakistan through Northern India and Nepal to Bangladesh would be decimated. Much of the area would become too hot and dry for the crop, placing the food supply of 200 million people at risk.

"The impacts on agriculture in developing countries, and particularly on countries that depend on rain-fed agriculture, are likely to be devastating," says Dr. Louis Verchot, principal ecologist at the World Agroforestry Centre in Nairobi, Kenya.

Wheat, the source of one-fifth of the world's food, isn't the only crop that could be clobbered by climate change. Cereals and corn production in Africa are at risk, as is the rice crop in much of India and Southeast Asia, according to Dr. Verchot.

In a cruel twist of fate, most of the hunger resulting from global warming is likely to be felt by those who haven't caused the problem: the people in developing countries. At the same time, it may be a boon to agriculture in richer northern countries more responsible for the greenhouse gas emissions driving climate instability.

"With climate change, the agricultural areas in Canada, Russia and Europe will expand, while the areas suited for agriculture in the tropics will decline," Dr. Verchot says. "Basically, the situation is that those who are well off now will be better off in the future, and those who are in problems will have greater problems."

This summer, I seemed to remember reading that world grain stocks were at levels that sparked panic buying in the 1970s. I spoke with a friend of mine who's an agriculture expert. He said that was basically true, but agreed the market doesn't seem to be getting too excited about it.

However, one of the hot parts of the commodities future markets these days is agriculture. Some people are making big bets there will be a food supply crunch.

A further excerpt:

Perhaps the best-known worrier about climate change and its impact on agriculture is Lester Brown, founder of the Earth Policy Institute, a U.S. environmental think tank, and proponent of the view that global warming and agriculture are on a collision course.

"It certainly looms large," Mr. Brown says of the threat posed to farming by a warmer world.

Mr. Brown says the global food larder is already so bare that the impact of global warming could be felt at any time — even as early as this summer — if it causes rising temperatures or changing precipitation patterns that lead to a crop failure in any major agricultural region.

The food surpluses of yesteryear have been nibbled down to the point where practically nothing is left in the bin for coping with even one disappointing harvest, he says.

"The unfortunate reality is that the cushion for dealing with climate change now is less than it's been for 34 years, because in six out of the last seven years world grain production has fallen short of consumption."

Furthermore, one of the solutions to global warming — using crops to produce clean-burning bio-fuels such as ethanol — would accentuate any harvest shortfalls because so much corn, sugar, and soybeans is now being diverted from the dinner plate to the gas tank.

The Earth Policy Institute tracks the world's stockpile of grain — the amount available in storage after accounting for annual use and production — and says it's down to only 57 days of consumption. This is close to the modern nadir, a period in the early 1970s of poor harvests when levels fell so low there was only enough for 56 days. That earlier period of short supply prompted a doubling of world grain prices — an indication of the possible consequences if global warming takes a bite out of harvests.