[Retric]

On the western half:

The 'low' areas have minimal rainfall and are 1KM over sea level. http://www.chinamaps.org/china/china-map-of-precipitation-an...

The high areas get a little more rainfall, but are mostly 4-5+km over sea level. http://www.china-food-security.org/data/maps/dem/dem_h.htm

Combine them and you can see why the population map looks the way it does. http://www.china-mike.com/china-travel-tips/tourist-maps/chi...

[Noseshine]

Uhm... Canada, not China. I responded to the comment that said

    > You could probably do the same in Canada fwiw.

I would not ask about China, I've seen enough documentaries about their deserts and high plateaus. Some of them about the silk road, which was not an easy one because of that geography.

[soundwave106]

From what I see, there's a pretty good correlation between the population density map (https://www.britannica.com/place/Canada/images-videos/Popula...) and the portion of Canada at least sporadically covered by permafrost. (http://www.enr.gov.nt.ca/state-environment/13-permafrost)

In addition to the rather obvious climate this implies (eg, rather cold), from what I understand, building anything on permafrost is very challenging.

[soperj]

"sporadically covered by permafrost" - I think you're confused as to the permanency of permafrost.