The United Nations food agency is warning rising prices fueled by historic drought could trigger a massive global food crisis similar to that of 2007 and 2008. The Food and Agriculture Organization’s food price index rose 6 percent in July after declining for the previous three months. The devastation of the U.S. corn crop by drought increased maize prices by almost 23 percent in July, while dry conditions in Russia helped push wheat prices up 19 percent. Shifting weather patterns also lifted the global sugar price, which rose 12 percent from June to July after unseasonable rains in Brazil hindered the sugarcane harvest. The United Nations says a potential global crisis is on the horizon if countries seek to restrict exports in order to control domestic prices, policies that sparked deadly protests around the world five years ago.