In one version of the story, a country with a lot of poor people suddenly experiences fast economic expansion, but only half of the people share in the new prosperity. The favored ones spend a lot of their new income on food, and unless supply expands very quickly, prices shoot up. The rest of the poor now face higher food prices but no greater income, and begin to starve.
There is also a high-tech version of the tale of two peoples. Agricultural crops like corn and soybeans can be used for making ethanol for motor fuel. So the stomachs of the hungry must also compete with fuel tanks.
He writes that the present crisis is caused not so much as a result of falling production, but accelerating consumption.