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Earth’s Carrying Capacity

A chance remark by an acquaintance about the world running out of food led me to revisit a paper written in 1979 by Prof. Cesare Marchetti, an iconoclastic physicist and materials scientist who likes to think outside the box. The title of his paper, published in the peer-reviewed journal “Energy” is “10 to the power of 12: a check on earth’s carrying capacity.”  The full text of this paper is available here:

Click to access MARCHETTI-076.pdf

A second writer on this topic, this time in a book called “How Many People can the Earth Support, (WW Norton, 1995)” is Joel Cohen, a mathematical biologist. Check this link for a summary of the book.

Click to access how%20many%20people%20can%20the%20earth-%20cohen.pdf

Even if the contents of Marchetti’s paper are seen as a thought experiment using back-of-the-envelope calculations, it still is a remarkable viewpoint that is worth remembering when faced with everyday accounts of the seemingly intractable flood of problems facing humanity: land degradation, overpopulation, the coming water crisis, climate change, environmental refugees, desertification, deforestation, sea level rise, ice melts at the polar caps, stratospheric ozone loss, excessive ground level ozone formation through traffic pollution and so on. The list of problems is seemingly endless, and reading a newspaper seems to involve ingesting a daily diet of hopelessness. In contrast, here are the concluding sentences from Cesare Marchetti’s and Joel Cohen’s papers respectively below.

Marchetti: It seems that the problems of growth are basically of cultural character. The Judeo-Christian axiom that the earth is given to man to be dominated, very material to western aggressive and destructive attitudes, may progressively be substituted by the Buddhist axiom that the earth is given to man to be contemplated; thanks to an enlightened use of technology.

Joel Cohen: More than ever before, the land that supported people became a partly human creation. For humans now, the notion of a static, passive equilibrium is inappropriate, useless. So is the notion of a static “human carrying capacity” imposed by the natural world on a passive human species. There is no choice but to try to control the direction, speed, risks, duration and purposes of our falling forward.

The conclusions I draw from these two very different studies are the same:

  1. there is no shortage of potential threats to human existence (always has been)
  2. there is no shortage of solutions
  3. there is plenty of work to do, so no danger of long-term unemployment
  4. subtle shifts in the public perception of problems can have tremendous long-term implications (the speed with which such shifts can occur is only the truly new element in global dynamics).


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