A very well written clear exposition of the problems facing the tropical world, which includes Africa, Latin America, and Asia. The low population density, poor soils, and disease are some of the things highlighted. Pierre Gourou founded the discipline of Tropical Geography and did quite a lot of fieldwork in the tropical world.
Today the UN would call this area the "Global South" as opposed to the wealth of the Temperate North.
Writing at a time of colonization of the tropics by Europe, Gourou was ambivalent about colonization but felt that Europe brought some degree of science and modernization to the tropics.
He nonetheless recognizes that the tropics could sustain civilization such as the Maya, India, and Southeast Asia.