Land use does not really get greener until we turn urban sprawl back to productive farm land. Making the city denser allows us to avoid sprawling on more land, but does not undo the damage.
So we might hope to mitigate the damage by having everyone huddled together with a great waste land surrounding the condensed city. By doing this we cut heating costs and allow us to all be close enough to walk to work, provided that no family has more than one person working. The condensed city can be served by ultra modern transportation facilities which will not be needed by most because we all live so close together. But because some people will be many km from work even in a condensed city of millions, we will build those ultra fast trains that will stop within the city only once or twice. Ultra fast is obviously for inter-city not intracity travel.
Building cities dense to start with would make sense, but trying to make a sprawling metropolitan area into a dense population area is more a concept than a reality within a lifetime. We make the core dense and immediately the outer areas fill up again, The effort of condensing the core is undone because it simply provides someone else the opportunity to sprawl, it attracts more people into not only the core but the hinterland too.
The way we make this go green is to install a dictator who prevents people from living outside of the core, forces the closing down of satellite cities.
We could imagine that our dictator could also insist everyone would be required to be happy with no green space in our concrete jungle. Because of course our objective in condensing the city is to eliminate all of those inefficient lawns and gardens, trees and boulevards that our sprawling cities inflict on us.
We go a bit further and force farmers to all live in a common apartment building for efficiency, and commute out to their farms up to 20 km each way, and of course we will provide modern mass transit for those farmers in such sparsely populated areas. Back to 1984.
