In This Review

How Many People Can the Earth Support?
How Many People Can the Earth Support?
By Joel E. Cohen
W. W. Norton, 1995, 416 pp.

With the earth’s population greater than 5.5 billion people and predicted to rise to 7.5 billion over the next two decades, this book’s title asks a perennial question. Cohen, a population biologist at Rockefeller University, has written a book at once erudite and entertaining. It contains a wealth of material about the earth’s population, resources, ecology, climate, social organization, and technology, and above all about the history of the earth’s various thinkers on the subject of its carrying capacity. Cohen illustrates how this question has been asked since at least the late seventeenth century, when Leeuwenhoek, generalizing from the Netherlands, estimated that the world could support 13.4 billion people. Since then, estimates for a sustainable population have varied from less than a billion to more than a trillion. Needless to say, various estimators have had very different ‘models’ of sustainable population in mind, and Cohen explores their usually implicit assumptions about geo- and bio-physics, human needs, and society in depth. His discussion is weakest on the last count, substantially understating, for example, the capacity of foreign trade to mitigate local deficiencies and augment world output. And what is the author’s answer? To reveal the conclusion would spoil the plot.