1000 square feet per person, for an apartment with a large balcony, or for a home, is very comfortable.
For 10 billion people to have 1000 square feet is 10 trillion square feet.
With 10-story buildings, 10 trillion square feet would require 1 trillion square feet of land.
1 trillion square feet is 92,900 square km…let’s round that up and say 100,000 square km.
Throw in an additional 100,000 square km of land for roads, parks, etc. – also a very comfortable amount, especially if you don’t waste most of it on cars – and you get 200,000 sq. km.
200,000 square km is a square with sides of roughly 450 km. It is about the size of Nebraska, or Belarus. In North America alone, there is already an estimated 230,000 km of urban land.
If you don’t like living in a spacious apartment 10 stories high, but prefer instead that your city have 5-story buildings, you would need 2 trillion square feet of land for apartments. That’s 186,000 square km of land. Double that number to add in public space and you get 372,000 square km. That’s a square with sides of just under 610 km. That’s smaller than Montana or Japan. China alone already has an estimated 520,000 square km of urban land, at least.
Whatever else we may lack, space is not it.
Future Economics 