Protests may spread as falling supplies caused by crop failures and greater use of grains for biofuels stoke inflation globally, the United Nations Food and Agriculture Organization said today. The World Bank says 33 countries from Mexico to Yemen may face social unrest because of surging food prices.

“We have seen riots around the world, and there’s risk that these will spread because of rising prices in countries where 50 percent to 60 percent of incomes go to foods,” FAO Director General Jacques Diouf said in New Delhi today. “The problem is serious.”