An index of 55 food commodities rose 2.2 percent to 236 points from 230.7 in January, the eighth straight gain, the UN’s Food and Agriculture Organization said on its website recently.

Rising food costs helped to fuel social unrest and riots in North Africa and the Middle East that toppled presidents in Tunisia and Egypt this year. Prices surged globally as a crop- destroying drought in Russia prompted the country to ban grain exports last year.

“Unexpected oil-price spikes could further exacerbate an already precarious situation in food markets,” David Hallam, the Rome-based FAO’s director of trade and markets, said in a statement. “This adds even more uncertainty concerning the price outlook.”

Global food prices probably will rise in the first half of this century because of an expanding population and higher incomes, slower crop-yield growth and the effect of climate change, Ross Garnaut, the Australian government’s climate-change adviser, said yesterday.

Food production will have to rise by 70 percent between 2010 and 2050 as the world population expands to 9 billion and rising incomes boost meat and dairy consumption, the FAO forecasts. Producing 1 kilogram (2.2 pounds) of pig meat can take 3.5 kilograms of feed, U.S. Department of Agriculture data shows.

(Parts of this article were written with content submitted by Bloomberg)