Scientists who study complex systems have predicted that precariously balanced food systems like those found in Egypt, Tunisia, and Yemen are poised to trigger political upheaval. Egypt’s uprising was triggered when Tunisia unexpectedly threw off a 30-year dictatorship last month. That uprising was triggered partly by food prices, which hit all-time highs in December. Since then demonstrators in Algeria, Morocco, Jordan and Yemen have also protested about high food prices.

In Egypt’s case, food may not have been the primary trigger, but bread is getting scarce in Egypt’s capital, Cairo. Bread production in Egypt is almost entirely controlled by the state. Egyptians are the world’s biggest wheat importers, and the government controls the ports where the grain is imported as well as the distribution trucks, flour mills, and even bakeries where bread is produced.

As workers join protests, grain is sitting on the docks and bakeries are closing for lack of flour. The interlocking dependencies that tie modern economies together spread dislocation further. Even where there is food, Egyptians have little money to buy it, as businesses and banks close, cash machines empty and wages dry up.

The result is a cascade effect, adding fuel to the fires of protest as centrally controlled systems break down and people go hungry.  This results in an increasing level of civil disorder.

Scientists are working on models that can better predict places these sorts of situations might emerge in the future.  For now, it seems the greatest risk is for countries that depend on imports and whose people spend a third or more of their incomes on food.