The real problem is not transportation or energy per se. It's the Green Revolution. The world currently has enough to eat (if in fact it does) because of petrochemicals.
Keep increasing the population at the current rate* and decrease (or even keep constant) the food supply**. What happens? Perhaps over here in Rich America our fat asses won't notice the problem for a while, but people will die. Millions of them. Billions of them? And all without considering the ramafications of transportation or other energy needs.
- Pie
* Heaven forbid we spend money on population control, right Mr. Bush?
**
http://www.2030spike.com/excerpts_chptr_2.htm
"Current corn yields in the United States, now 130 bushels an acre, [would fall] to around 30 bushels."