Joel K. Bourne Jr, National Geographic, June 2009.
Full text http://ngm.nationalgeographic.com/2009/06/cheap-food/bourne-text
Some incredible (but also some depressing) photos at  http://ngm.nationalgeographic com/ 2009/06 /cheap-food/stanmeyer-photography
 
It is the simplest, most natural of acts, akin to breathing and walking upright. We sit down at the dinner table, pick up a fork, and take a juicy bite, oblivious to the double helping of global ramifications on our plate. Our beef comes from Iowa, fed by Nebraska corn. Our grapes come from Chile, our bananas from Honduras, our olive oil from Sicily, our apple juice-not from Washington State but all the way from China. Modern society has relieved us of the burden of growing, harvesting, even preparing our daily bread, in exchange for the burden of simply paying for it. Only when prices rise do we take notice. And the consequences of our inattention are profound.

Last year the skyrocketing cost of food was a wake-up call for the planet. Between 2005 and the summer of 2008, the price of wheat and corn tripled, and the price of rice climbed fivefold, spurring food riots in nearly two dozen countries and pushing 75 million more people into poverty. But unlike previous shocks driven by short-term food shortages, this price spike came in a year when the world's farmers reaped a record grain crop. This time, the high prices were a symptom of a larger problem tugging at the strands of our worldwide food web, one that's not going away anytime soon. Simply put: For most of the past decade, the world has been consuming more food than it has been producing. After years of drawing down stockpiles, in 2007 the world saw global carryover stocks fall to 61 days of global consumption, the second lowest on record.

"Agricultural productivity growth is only one to two percent a year," warned Joachim von Braun, director general of the International Food Policy Research Institute in Washington, D.C., at the height of the crisis. "This is too low to meet population growth and increased demand."

High prices are the ultimate signal that demand is outstripping supply, that there is simply not enough food to go around. Such agflation hits the poorest billion people on the planet the hardest, since they typically spend 50 to 70 percent of their income on food. Even though prices have fallen with the imploding world economy, they are still near record highs, and the underlying problems of low stockpiles, rising population, and flattening yield growth remain. Climate change-with its hotter growing seasons and increasing water scarcity-is projected to reduce future harvests in much of the world, raising the specter of what some scientists are now calling a perpetual food crisis.

So what is a hot, crowded, and hungry world to do?

That's the question von Braun and his colleagues at the Consultative Group on International Agricultural Research are wrestling with right now. This is the group of world-renowned agricultural research centers that helped more than double the world's average yields of corn, rice, and wheat between the mid-1950s and the mid-1990s, an achievement so staggering it was dubbed the green revolution. Yet with world population spiraling toward nine billion by mid-century, these experts now say we need a repeat performance, doubling current food production by 2030. <cut>

How we did it before?  http://ngm.nationalgeographic.com/2009/06/cheap-food/ green-revolution- illustration
In other words, we need another green revolution. And we need it in half the time.
 http://ngm.nationalgeographic.com/2009/06/cheap-food/new-green-revolution-illustration