Megaskyscrapers??

A recent article claimed that we could accommodate growing world population with less strain on resources by building "vertical cities":

A vertical city ... is an "arrangement of interconnected mega towers" that could support hundreds of thousands of people. These buildings could be as tall as 400 floors and contain housing, stores, hospitals, schools, farms, and outdoor spaces, all in one building or series of connected structures.

A quick reality check:

Going from sprawl, at about 2 people per acre, to the density of Paris, about 100 people per acre, saves a significant amount of land: close to 1/2 acre per person.

Going from the density of Paris to megaskyscraper density saves an insignificant amount of land - less than 1/100 acre per person.

Looking not only at the land the city uses directly but at all the resources people use, the average American has an ecological footprint of over 20 acres - representing all the resources he or she uses.
It requires less than 1/100 acre per person to live at Paris densities rather than in megaskyscrapers, a negligable portion of total ecological footprint.

It undoubtedly uses more resources to build these megaskyscrapers than to build the six to eight-story buildings common in Paris, since they must need very hefty steel skeletons. They probably also require more heating and cooling, since they are more exposed to the elements. The extra resource use may well be greater than the small savings of energy used for transportation and of other resources.

Someone should calculate the total ecological footprints of a city build of megaskyscrapers and a city built at Paris densities, both using the best possible technologies to conserve resources. They would be close, but the megaskyscrapers would probably have a greater footprint.

Yes, sprawl wastes a lot of resources, but let's not go from one ridiculous extreme to the other. Which gives a better and more human-scale quality of life: Paris densities or megaskyscrapers?
The answer is obviously Paris - and it is wrong to imply that megaskyscrapers would save a significant amount of land compared with the midrise urban densities of Paris.