Only part of Pakistan is habitable. Pakistan has large inhabitable areas. Including three huge mountain rages: Himalaya, the Karakoram and the Hindukush. In these areas people live only in narrow valleys next to river. (when the the river floods, they are screwed).

This is the way people have always lived (except for very modern times)

I think they mean to say that comparing the Pakistani figures (which include low population mountains and deserts) to Belgium (which is pretty much entirely arable and flat as a pancake) is a bit silly.

Human societies have always crowded riverbanks. Until very recent times.

Both statements can be true at the same time

* this is a common pattern of settlement

* the different geographies of two countries make a very simple (population / land area) density figure misleading, because Belgium is nearly 100% riverbank or floodplain and Pakistan is not

This is such a known problem that the US Census already has a different density measurement method, population-weighted density: https://www.smartcitiesdive.com/ex/sustainablecitiescollecti...

Although Belgium certainly isn't as rugged as Pakistan, it's far from flat and especially in Wallonia population is very concentrated along one valley (the sillon Sambre et Meuse):

https://www.researchgate.net/profile/Kobe-Boussauw/publicati...

As a result, the region has a population density of 240/km² (only slightly less than Pakistan) but about 2/3rds of the population is in this valley representing 1/16th of the area of Wallonia. Flanders is mostly flat and more evenly settled.

This is actually more similar than I expected to the population distribution in Pakistan, with Punjab being a flat plain with an evenly distributed population, and the rest of the country being mostly settled along one river. By the way, Belgium also suffered a large flooding event last year in this valley, although nowhere near as deadly as what is happening in Pakistan.

*uninhabitable

I suppose the size of the territory and landscape is what makes all the difference.

Macau is amazingly densely populated, but at the same time the same density as Paris, but 1/3 of the size. It's an hour walk from one end to the other according to Google Maps.

India on the other hand is just 10% denser than Belgium, but doesn't feel like that when you look at photos of its cities and trains loaded with people.

It's more about designing good systems. Belgium is a developed country with excellent infrastructure whereas India is a developing country with poor infrastructure

322/km² in the UK

[0] Ourworldindata.org

Within the UK the distribution is far from uniform as well:

https://www.sheffield.ac.uk/news/nr/land-cover-atlas-uk-1.74...

e.g. More land is peat bogs than is built up.

521/km^2 here to your north in Holland...