[Webstral]

Petroleum and inorganic fertilizers are musts for modern mechanized agriculture. They aren't necessary for supporting a large population or a high population density, as China's history illustrates. However, they are necessary for the maintenance of a modern society and a modern economy in which a small part of the labor force is involved in food production. If you put 75% of the labor force back into food production, shortages of almost any resource can be mitigated with labor. One of the principle variables is how quickly a nation can be transitioned and what happens with those who don't make the transition. Either way, we're talking about the end of the world as we know it. Some nations are in a better position to transition the majority of their labor pool into food production using labor-intensive methods--if in fact there is a transition at all.