Demographics
In the Bible, God says to Adam and Eve, “Be fruitful and multiply…”. Believers and non-believers have been following that advice for millennia, but it is only in the 20th century that it began to be clear that humans might actually be capable of overrunning the planet. While the growth rate of earth’s population has begun to abate, the built-in momentum of population growth is bound to continue for at least a couple of decades into the future. Because we are now in danger of producing more humans than we can feed and house, the earth’s population and demographics are almost certain (barring even more horrific possibilities) to be important issues until it is clear that mankind has gotten its reproduction under control. It is not too apocalyptic to say that the future human condition is critically dependent on the carrying capacity of the earth and on mankind’s ability to control its reproduction.
How Many People Can the Earth Support? - 1995
Joel E. Cohen
Learn more (W. W. Norton & Co.)
This is still the classic work on the human carrying capacity of the earth. The book begins with a history of human population and an explanation of demographics and how populations change. From there, Cohen explores a wide variety of population projections for the earth (and how poorly they have fared compared with reality). He then explores a variety of projections for the earth’s carrying capacity. These explore notions of carrying capacity based on a number of constraints including land, water, agriculture, sunlight, natural resources, and the like. (The answers for earth’s carrying capacity range from 4 billion – which we’ve already passed – to more than a trillion). Cohen makes some good, technical suggestions for paying attention to population, but for me, the most interesting concept in the book is the ‘demographic transition’. As a historical pattern, the demographic transition has four stages. The first stage has high birth and death rates that are nearly equal. In the second stage, the death rate drops while the birth rate stays high. In the third stage, the birth rate falls, and in the fourth stage, the birth and death rates are both low and roughly equal. This is a pattern that has recurred in most developed and many developing countries, but so far, no known mechanism explains the data.
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