r books. Similarly, trading in grain futures is in a sense trading in water futures.

Falling water tables are already adversely affecting harvests in some countries, including China, the world’s largest grain producer. Overpumping has largely depleted the shallow aquifer under the North China Plain, forcing farmers to turn to the region’s deep fossil aquifer, which is not replenishable. Wheat farmers in some areas of the Plain are now pumping from a depth of 300 meters, or nearly 1,000 feet.

Overall, China’s grain production has fallen from its historical peak of 392 million tons in 1998 to an estimated 358 million tons in 2005. This drop of 34 million tons exceeds the Canadian wheat harvest. China largely covered the drop-off in production by drawing down its once vast stocks until 2004, at which point it imported 7 million tons of grain.

Water shortages are even more serious in India simply because the margin between actual food consumption and survival is so precarious. At this point, the harvests of wheat and rice, India’s principal food grains, are still increasing. But within the next few years, the loss of irrigation water could override technological progress and start shrinking the harvest in some parts of the country, as it is already doing in China.

After China and India, there is a second tier of countries with large water deficits—Algeria, Egypt, Iran, Mexico, and Pakistan. Three of these—Algeria, Egypt, and Mexico—already import much of their grain. However, in a parallel move with China, water-short Pakistan abruptly turned to the world market in 2004 for imports of 1.5 million tons of wheat. Its need for imports is likely to climb in the years ahead.

The Middle East and North Africa—from Morocco in the west through Iran in the east—has become the world’s fastest-growing grain import market. The demand for grain is driven both by rapid population growth and by rising affluence, much of the latter derived from the export of oil. With virtually every country in the region pressing against its water limits, the growing urban demand for water can be satisfied only by taking irrigation water from agriculture.

Egypt, with some 74 million people, has become a major importer of wheat in recent years, vying with Japan—traditionally the leading wheat importer—for the top spot. It now imports 40 percent of its total grain supply, a number that edges steadily upward as its population outgrows the grain harvest produced with the Nile’s water.

Algeria, with 33 million people, imports more than half of its grain, which means that the water embodied in the imported grain exceeds the use of water for all purposes from domestic sources. Because of its heavy dependence on imports, Algeria is particularly vulnerable to disruptions, in the event of a world grain shortage.

Overall, the water required to produce the grain and other farm products imported into the Middle East and North Africa last year equaled the annual flow of the Nile River at Aswan. In effect, the region’s water deficit can be thought of as another Nile flowing into the region in the form of imported grain.

It is often said that future wars in the Middle East will more likely be fought over water than oil, but the competition for water is taking place in world grain markets. It is the countries that are financially the strongest, not necessarily those that are militarily the strongest, that will fare best in this competition.

Knowing where grain import needs will be concentrated tomorrow requires looking at where water deficits are developing today. Thus far, the countries importing much of their grain have been smaller ones. Now we are looking at fast-growing water deficits in both China and India, each with more than a billion people.

Each year the gap between world water consumption and the sustainable water supply widens. Both aquifer depletion and the diversion of water to cities will contribute to the growing irrigation water deficit and hence to a growing grain deficit in many water-short countries.

Because overpumping to satisfying growing food demand virtually guarantees a future drop in food production when aquifers are depleted, many countries are in essence creating a “food bubble economy”—one in which food production is artificially inflated by the unsustainable mining of groundwater.

The effects of overdrafting were not obvious when farmers began pumping on a large scale a few decades ago. The great attraction of pumping groundwater in contrast to large-scale surface water systems is that farmers can apply the water to crops precisely when it is needed, thereby maximizing water use efficiency. Groundwater is also available during the dry season, enabling many farmers in mild climatic regions to double crop.

In the United States, 37 percent of all irrigation water comes from underground; the other 63 percent comes from surface sources. Yet three of the top grain-producing states—Texas, Kansas, and Nebraska—each get 70–90 percent of their irrigation water from the Ogallala aquifer, which is essentially a fossil aquifer with little recharge. The unusually high productivity of groundwater-based irrigation means that the food production losses will be disproportionately large when the groundwater runs out.

At what point does water scarcity translate into food scarcity? In which countries will the irrigation water losses from aquifer depletion translate into a drop in grain production? David Seckler and his colleagues at the International Water Management Institute, the world’s premier water research group, summarized this issue well: “Many of the most populous countries of the world—China, India, Pakistan, Mexico, and nearly all the countries of the Middle East and North Africa—have literally been having a free ride over the past two or three decades by depleting their groundwater resources. The penalty for mismanagement of this valuable resource is now coming due and it is no exaggeration to say that the results could be catastrophic for these countries and, given their importance, for the world as a whole.”

Since expanding irrigation helped triple the world grain harvest from 1950 to 2000, it comes as no surprise that water losses can shrink harvests. With water for irrigation, many countries are in a classic overshoot-and-decline mode. If countries that are overpumping do not move quickly to reduce water use and stabilize water tables, then an eventual drop in food production is almost inevitable.

Adapted from Chapter 3, “Emerging Water Shortages,” in Lester R. Brown, Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble (New York: W.W. Norton & Company, 2006), available for free downloading and purchase at www.earthpolicy.org/Books/PB2/index.htm.