Answer:
Isolated hostile terrain
Step-by-step explanation:
Lower population density is expected in areas that do not have agreeable climates or that are far removed from major world trade centers. One of the least densely populated countries, Mongolia, is located on the cold Siberian steppe and has no maritime border.
Other sparsely populated areas like the Sahara desert are too hot or extreme and have scarce water resources. Yet other sparsely populated nations like Australia have some temperate climates but were not settled on a large scale until the 1800s.