I can't help but think things out in terms of financial outcomes. When I began writing this blog it was to forewarn clients, family, and friends about what was - at the time - the coming collision of the housing crash and Oil price surge and what it was likely to do to their life savings.
Now, using that framework I want to expand on my thought that "mega cities" will become "uninhabitable" in an energy constrained world.
First, one must accept the assumption - that serious energy constrainment (I know, the word is not in the dictionary... but I like the way it sounds) is coming, at least in how industrial age energy is currently defined. If you reject this, then you will reject the rest of my assertions.
"Amateurs talk strategy. Professionals talk logistics." - unknown
Mega-cities: New York, Sao Paulo, Tokyo, L.A. et al are technological islands - they must import everything. Think about that for a minute. These regions have supply chain infrastructure/liabilities that are completely reliant on the smooth functioning of myriad other systems: commuting and transportation systems to bring workers in, maintenance systems, worker healthcare systems, food distribution systems... now take a look at what is happening in Tokyo right now. Somewhat unaffected directly by the earthquake and tsunami their distribution system has failed miserably.
My parents-in-law live near Osaka another couple hundred miles further than Tokyo from the disaster... and they have empty stores and rolling blackouts. The only difference is this: In a world wide energy constrained system, one like Japan is experiencing now, the cavalry is NOT coming because the cavalry is energy constrained, too. So, here you are on this energy constrained technological island (not Japan, ALL mega-cities are "technological islands) that requires the importation of everything AND it requires the exportation of all of the stuff previously imported (though in a somewhat different form): Refuse and sewage.
My assertion is pretty simple, really. Mega-cities will not be able to logistically support their populations with food, water, and other supplies, and will be unable to process the refuse and sewage during a period of serious energy constrainment... and the outcome would unfold at lightening speed... and, this will have seriously negative effects on property values and employment, and hence banking, within these mega-cities. These cities will depopulate, and will do so long before the "roving bands of looters" scenario unfolds (not that people won't take what they need... they will simply run out of stuff to take and with food imports into the technological island falling will need to find better ways to spend their time).
The economic strains coming from all of this would be profound. Why spend your life working to acquire assets that will, by mathematical necessity, become nearly worthless? You'd be far better doing just about anything else. 20 million people living on a postage stamp piece of land is not a well considered living situation as currently constructed here in the U.S. in the absence of energy inputs in order to provision them.
My friend the Mad Scientist has reminded me often that India has triple the population and roughly the same land area, and that is true (of course, India does not have the U.S. need for space heating). I did not say we couldn't live with what we have... I said that the mega-cities would depopulate and the property prices would decline dramatically with all of that outcome's effects on banking. Americans will have a very hard time adjusting to an Indian standard of living.
If you accept my analysis so far... why would you send your offspring to be educated, at great expense in years and treasure, in a field that will require him/her to live in a mega city in order to make a living? Why pay big bucks to live in squalor? Wouldn't you be better off educating them in something very practical (engineering, dentistry, plumbing.... one of my buddies in Florida is a Dentist of sorts... he reads my stuff and recently told me that his son is going to be studying engineering in undergrad, and credits me somewhat. I was thrilled to hear it, and even more thrilled to here that his son wants to go to dental school after engineering college) acquiring productive farm land (I know I have been beating this drum for years... and farm prices are up BIG... but my bet is that they are a far better investment than a liberal arts degree from a "progressive" leaning college), opening a family business, and getting acclimated to your new life? Why would you continue to pay the mortgage on a condo that will be bird nesting grounds? Or live in a home with a property tax bill that is draining the life from you? Why would you buy an expensive automobile?
The population flight to the mega cities of the past 100 years was a flight towards the energy importing, technological islands I mentioned above. As the energy available for import into these regions declines, so will the pull that these regions have exerted on the population. The events unfolding in Japan will put nuclear on hold, long enough, to demolish the attempt to cushion the energy blow from Oil - not that I necessarily agree that doing so is a good idea; or not - long enough that my scenario, I think, is the most likely scenario to unfold.
Lastly, the rules seem to change every f$&**!! day. These are the rules as I see them given the latest data. If the data changes, I will change my mind.