One thing I think you are overlooking is the fact that it needs to be profitable before people are tempted to do that, Flint.
Right now, profitmargins on food are (artificially) low, it would take generations before these kind of terrain adaptions would pay off.
The other side of that story is, that if food prices go up with a significant amount, starvation will flourish again.
To be honest, I think this is all a self-regulating problem. If food production stays on this level, and the population keeps growing, either a war or starvation will take the population down.
The irony of it all is that in large parts of Asia large families are maintained to work on farms. If everyone does this, the netto gain is negligible if not 0. (more people produce more, but require more food).
