There are more than a billion people in the world that go to bed hungry. Some till the soil on small farms. Some live in the slums of big cities. Each is working as hard as they can but their labor provides only a fraction of what they need to fill their bellies.
What changes can cause these people to lose their tenuous grasp on life? What changes could cause more poor people to join their precarious state? What larger changes could transform your child or grandchild into the equivalent of a Somali war orphan; no parents, no home, getting their food out of a dumpster, and carrying a gun in a militia to keep life in their bodies.
Certainly, if a subsistance farmer's soils deplete or salinize this could happen. Certainly if the water table drops and it takes more work to raise it to the plants this could happen. It could happen if land became more valuable growing, animal feed, or crops to make auto fuel. Then land would be purchased from food farmers. They would have the money in their pocket but their decendents would soon be landless in the slums.
These actions and processes are already happening. Slums, with people living at subsistence, are growing. More people are eating meat. More people are driving cars using crop based fuel. More expensive fuel makes it more expense to plow, pump water, fertilize, harvest, process and deliver the food.
All these processes and actions contribute to a growing number of people starving to death. Changes in the price of food will effect more than the weakest billion. Doubling the price of food moves everyone down the wellbeing chain.
You and I in the developed world who spend 5% of our income on food would call this belt tightening. However, people who have been making two dollars a day and spending 50% on food will now be going to bed hungry.
Now if the cost of fuel doubles again then the cost of food could double again. Then the second billion would starve to death. Remember the first billion are gone.
The third billion (those making 5-6 dollars a day) can see the handwriting on the wall. They are next to be starving. And since they live in close proximity to those that just starved to death. They know their future.
The first billion were not happy to starve to death but they were too poor to save themselves. The second billion were not happy to starve to death and while they rioted and looted their neighbors they were "contained - killed." But you and I (who don't know too many people living on 5 dollars a day) where probably far enough away to keep out of reach of this riot of the second billion starving people.
The third billion will have received the "sliding-down-to-starrvation" message before conditions got really desperate for them. They tried to move to where conditions were better-- same as immigrants have since time began. But in this future, no one will take them. It is too dangerous to have a slum near your house even if it does provide cheap domestic help. The more the third billion can not migrate the more social conflict erupts in their home country.
The lower and middle class (Billion 4 and 5) also respond to scarcity and higher prices. They hoard. They band into groups and fortify internal resources and protect their supply routes. They make sure resources in distant lands continue to flow homeward.
Of course all this offensive and defensive effort diverts resources from supporting wellbeing. This creates more scarcity and higher prices. Which lowers everyone's wellbeing. Everyone becomes less generous. Which means the third billion trapped at home in slums is now in for their turn at starvation.
They have had time to think about how they are going to handle this. They have had time and resources to prepare. And they are not going quietly into the night as was accepted by the first billion. And they cannot be bared from migration like the second.
The third billion storm any barricade between them and food. And they have nothing to lose even if the owners retaliate with a genocidal response. This round of conflict -- the potential for the third billion starving will create a social conflict that will collapse civilization.
And if it does not then fourth billion will. And if I understated then civilization will have collapsed under the crush of the second billion.
You Child or grandchild, in Chicago, if civilization collapses will be just like a Somali war orphan.
Of course, you don't want to go to this destination. But what makes you think we are not going there!!