History includes several examples of times and places in which hunger and a desire for food has caused political or social troubles: Russia in 1910 and 1917, the U.S. and Germany in the 1930s, the Soviet Union in the 1980s and 90s, and certain African countries in the 1970s up until the present day (sadly).
About two years ago, the price of wheat worldwide spiked and products such as bread and pasta almost doubled in price. The video below shows a survey of how different countries' news stations covered the crisis. Notice that in the U.S. the story focused on how much more pastries would cost, while in Egypt and Pakistan people were rioting and in a state of panic over the higher price and lower supply of bread:
In movies, there is one great example of what might happen in an earth that is overcrowded and polluted. Without the land to grow food, or clean oceans from which to find seafood, the company goes to drastic measures to provide food.
Soylent Green, the main character finds out a terrible secret about what the people of New York have been eating. He also solves the mystery of where all of the missing rioters went after being arrested by the police. He tries to warn the others!