CALIFORNIA SO CROWDED
Its gotten so crowded in California. We all now have to fight for every little space of freeway . Fight for housing. 50 thousand homeless in the streets because housing is to expensive. Forty years of Californian being overrun has destroyed our great state. Just the amount of hours of our lives lost on the freeways has caused so many of us to take more drugs or drink a lot more to deal with what we have let our world become from the mass people invasion of the last 40 years. We're rats tearing each other apart now. So Sad! Our politicians have failed us terribly 
Not to mention the water depletion situation going on there :(
Water is the world's new gold
The wars of the future will be fought over it! Clashes happen even today here and there by small factions for control of areas that have a source of freshwater. That’ll be a sad time to be alive. If an cost effective source of energy could be used such as tidal turbines or something, I think desalination of ocean water via a process called reverse osmosis would work. But like you state above, the problem would be providing for the overwhelming number of people