RONALDO SCHEMIDT/AFP

At the end of January, 75,000 angry people marched in Mexico City to protest the exorbitant price of tortillas. Like much of what happens in Latin America these days, it didn't attract much attention in the United States. But the discontent of poor Mexicans is just the tip of the iceberg in a region that depends heavily on corn.

What's going on? The ethanol boom in the United States is pushing up the price of corn, and that means food prices in the Western Hemisphere and around the world are also on the rise. For a Bush administration deeply worried about anti-American leftism in Latin America, that's a problem. As Lester Brown of the Earth Policy Institute puts it in this week's Seven Questions:

Our refrigerators are stuffed with corn: milk, eggs, cheese, chicken, pork, beef, yogurt, ice cream—these are all corn products. The risk is that by converting so much of our grain into fuel for cars, we will drive up the price of grain and create chaos in the world grain markets. This could mean urban food riots in scores of low- and middle-income countries around the world.

How can we avoid this dangerous situation? Read the interview to find out.