How can land be underpopulated? What happens when you don’t have much labor is the labor prices go up (wages increase).

I can’t help but suspect from your other comments in this thread you are just trying to justify your a priori want for more immigration, why?

I think we can safely say a place that has an extremely low population density and actively pays people to go inhabit parts of it is very underpopulated relative to other places in the world.