These are all climate-change issues, but they have something else in common: food. Copenhagen will be about climate, of course, but in a fundamental sense, it must also be about whether we will have enough to eat in the decades to come.


We need not go beyond ice melting to see that the world is in trouble on the food front. As the Greenland and West Antarctic ice sheets continue to shrink, sea levels will rise, threatening rice harvests around the globe. Recent projections show that the sea could rise up to six feet this century (if the Greenland ice sheet were to melt entirely, it would rise by 23 feet). According to the World Bank, it would take only a three-foot rise in sea level to cover half the rice fields in Bangladesh, a country of nearly 160 million people. Such an increase would also inundate much of the Mekong Delta, which produces half the rice crop in Vietnam, the world's No. 2 rice exporter. And it would submerge parts of the 20 or so other rice-growing river deltas in Asia.

Melting mountain glaciers are even more worrisome. The World Glacier Monitoring Service in Switzerland recently reported the 18th consecutive year of shrinking mountain glaciers around the world, from the Andes to the Rockies, from the Alps to the mountain ranges of Asia. Of these, the disappearance of glaciers in the Himalayas and on the Tibetan plateau threatens to shrink food supplies most sharply. Their annual ice melt sustains the major rivers of India and China -- the Indus, Ganges, Yangtze and Yellow -- during the dry season. And this water in turn supplies irrigation systems.

Yao Tandong, one of China's leading glaciologists, warned last year in the journal Nature that two-thirds of the country's glaciers could be gone by 2050, and he has said that "the full-scale glacier shrinkage in the plateau regions will eventually lead to an ecological catastrophe."

It will also lead to a humanitarian catastrophe. China is the world's leading producer of wheat. India is No. 2. These two countries also dominate the world's rice harvest. But unlike in the United States (the third-largest wheat producer), where wheat is watered largely by rainfall, most crops in China and India are irrigated. The vanishing of mountain glaciers in Asia therefore represents the biggest threat to the world food supply that we have ever seen.