Melting Mountain Glaciers Will Shrink Grain Harvests in China and India ... predictably massive threat to food production

March 20, 2008 - 3 | Copyright © 2008 Earth Policy Institute | Melting Mountain Glaciers Will Shrink Grain Harvests in China and India | Lester R. Brown

The world is now facing a climate-driven shrinkage of river-based irrigation water supplies. Mountain glaciers in the Himalayas and on the Tibet-Qinghai Plateau are melting and could soon deprive the major rivers of India and China of the ice melt needed to sustain them during the dry season. In the Ganges, the Yellow, and the Yangtze river basins, where irrigated agriculture depends heavily on rivers, this loss of dry-season flow will shrink harvests.

The world has never faced such a predictably massive threat to food production as that posed by the melting mountain glaciers of Asia. China and India are the world’s leading producers of both wheat and rice—humanity’s food staples. China’s wheat harvest is nearly double that of the United States, which ranks third after India. With rice, these two countries are far and away the leading producers, together accounting for over half of the world harvest.

The Intergovernmental Panel on Climate Change reports that Himalayan glaciers are receding rapidly and that many could melt entirely by 2035. If the giant Gangotri Glacier that supplies 70 percent of the Ganges flow during the dry season disappears, the Ganges could become a seasonal river, flowing during the rainy season but not during the summer dry season when irrigation water needs are greatest.

Yao Tandong, a leading Chinese glaciologist, reports that the glaciers on the Tibet-Qinghai Plateau in western China are now melting at an accelerating rate. He believes that two thirds of these glaciers could be gone by 2060, greatly reducing the dry-season flow of the Yellow and Yangtze rivers. Like the Ganges, the Yellow River, which flows through the arid northern part of China, could become seasonal. If this melting of glaciers continues, Yao says, “[it] will eventually lead to an ecological catastrophe.”

Even as India and China face these future disruptions in river flows, overpumping is depleting the underground water resources that both countries also use for irrigation. For example, water tables are falling everywhere under the North China Plain, the country’s principal grain-producing region. When an aquifer is depleted, the rate of pumping is necessarily reduced to the rate of recharge. In India, water tables are falling and wells are going dry in almost every state. ...