This will be the Arab world's next battle

Long after the political uprisings in the Middle East have subsided, many underlying challenges that are not now in the news will remain. Prominent among these are rapid population growth, spreading water shortages, and growing food insecurity.

In some countries grain production is now falling as aquifers � underground water-bearing rocks � are depleted. After the Arab oil-export embargo of the 1970s, the Saudis realised that since they were heavily dependent on imported grain, they were vulnerable to a grain counter-embargo. Using oil-drilling technology, they tapped into an aquifer far below the desert to produce irrigated wheat. In a matter of years, Saudi Arabia was self-sufficient in its principal food staple.

But after more than 20 years of wheat self-sufficiency, the Saudis announced in January 2008 that this aquifer was largely depleted and they would be phasing out wheat production. Between 2007 and 2010, the harvest of nearly 3m tonnes dropped by more than two-thirds. At this rate the Saudis could harvest their last wheat crop in 2012 and then be totally dependent on imported grain to feed their population of nearly 30 million.

The unusually rapid phaseout of wheat farming in Saudi Arabia is due to two