“This is a silent tsunami,” says Josette Sheeran of the World Food Programme, a United Nations agency. A wave of food-price inflation is moving through the world, leaving riots and shaken governments in its wake. For the first time in 30 years, food protests are erupting in many places at once.

　　Famine traditionally means mass starvation. The measures of today's crisis are misery and malnutritio. The middle classes in poor countries are giving up health care and cutting out meat so they can eat three meals a day. The middling poor, those on $2 a day, are pulling children from school and cutting back on vegetables so they can still afford rice. Those on $1 a day are cutting back on meat, vegetables and one or two meals, so they can afford one bowl. The desperate—those on 50 cents a day—face disaster.

　　Roughly a billion people live on $1 a day. If, on a conservative estimate, the cost of their food rises 20%, 100m people could be forced back to this level, the common measure of absolute poverty. Because food markets are in turmoil, civil strife is growing; and because trade and openness itself could be undermined, the food crisis of 2008 may become a challenge to globalisation.