Lawns and pavement have got to go.
Let's make this clear from the beginning: I am not advocating a government response to suburban sprawl. I think the price of transportation will soon outweigh any benefit living fifty miles away from your job provides. Also, people tend to get rebellious when seemingly trivial details about lifestyle are enforced by government regulations. (It's my land and I'll do what I want!)
We as a society need to shame everyone into change. We need to embarrass the pants off wasteful people. Just as comics mock anyone driving an SUV, we need to make absolutely certain that we get ticked at people (and institutions) that value unsustainable aesthetics. Just like any other fad, lawns and pavement have to fade, and the only way that will happen is if they are made undesirable through societal consensus.
So from now on, anyone with a lawn is a dork.