Rising grain prices do not have to mean hunger in Africa. For years small farmers in Africa (and everywhere else) have been hobbled by the competition from subsidised 1st World grain farmers, and "Food Aid". Input costs in rural Africa ensured that maize could not be grown profitably as long as world market prices remained at $2something a bushel. Now perhaps there is actually incentive to grow food crops in countries like Zambia.
With the use of food grain as feedstock for Ethanol production, the demand for grain worldwide has jumped, and so have prices. Now people can potentially start out with very little, plant crops, and earn money.
Quite possibly the cycle of poverty and hunger can be broken, for many. For town dwellers of course, that will take longer. They will have to wait for the newly solvent farmers to need goods and services they can provide.
Perhaps this is the key to the different rates of development in Asian countries, as contrasted with Africa in general - rice has always been a profitable crop, while the crops usually planted in Africa have been subject to artificially low prices.