Society grew because we made laws to protect people from killing and stealing from each other. Now for society to keep growing we have to make new laws that do not allow people to kill others with pollution and its effects.
Just imagine the hilarity when a society made up of 20 billion people living efficient, highrise-dwelling, car-pooling, vegetarian, recycling kind of lives breaks down.
As opposed to what other kind of lives? Suburban and rural folks will be just as screwed when they don't have a wal-mart or a costco to get supplies from.