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How Many People Can the Earth Support? Paperback – September 17, 1996
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From Publishers Weekly
Copyright 1996 Reed Business Information, Inc.
Top Customer Reviews
This book asks many of the right questions. And it admits that we don't have all the answers. But it does give some clues about where we may be headed.
Cohen shows that basically, if we want to support people indefinitely on 3500 kilocalories per day from wheat energy, with 9000 cubic kilometers of annual fresh water supply, well, we can support only 5 billion people. We're already beyond that. Right now, we're using up resources at an incredible rate. And while the Earth could support 10 billion people in theory, it is hard to see how it could do that for long in practice.
The author thinks that we'll never get to the absolute maximum that the Earth can support. Most people would all be right on the edge of starvation, and we'd simply be unable and unwilling to stay in that state indefinitely. But I did realize after reading this book that we could stay at about 5 billion people for a very long time if we put our minds to it. Standards of living would not be high, but they would be tolerable for the majority, and the ones who found such a life acceptable would keep having children who found it acceptable.
Those of us who have political views ought to wonder if time is on our side or not. And that is why I think it makes sense to try to imagine what options are available for our mutual future. That's why I think this book is worth reading.
Having said this by way of praise, I would also like to note a couple weaknesses. The most obvious one is something that Cohen simply can't help. Eighteen years after publication some of the data is out of date. Therefore, the careful reader ought to find more recent sources for the data that Cohen cites.
Cohen also seems to underestimate the ability of human beings to find new resources and new ways of economically abstracting existing resources. As some have pointed out, there are no resources per se. Something becomes a resource only when someone finds a use for it. (Case in point: For most of human history petroleum was not a resource.) Moreover, many resources are available in far greater abundance than the official calculations would lead one to believe. Such calculations are generally based on known supplies that can be economically extracted. As we know from the huge reserves of oil that are currently being extracted from shale through hydraulic fracturing (fracking), past estimates of oil reserves seriously underestimated the amount of oil that is now available to us.Read more ›
Mr. Cohen, when discussing these difficulties, assumes often a quite sarcastic view about the myriad of (often precise) estimates about future populations and Earth's carrying capacity presented in the book. The fact is that since the 19th century, with a marked improvement in health conditions, we've been going through a period of very rapid populational expansion, the greatest growth rate (about 2.1%) being observed during the 1960s. The problem is that any positive rate is not sustainable in the long run; either birth rates must fall or death rates increase. How and when places like India and Africa, for example, do experience the so called demographic transition shall determine the maximum population the planet will have to support.
The book is organized in (i) estimates for past human populations, (ii) estimates for future populational growth, (iii) estimates for the Earth’s human carrying capacity, and (iv) a conclusion.
The author builds only one numerical exercise to evaluate the Earth’s carrying capacity, based on the availability of fresh water. The figures vary by a factor greater than 20 depending on assumptions about how much fresh water is sustainably retrievable and the meat content in diets.
My only complain about this book is its age: the latest numbers presented are from 1995, and a lot has changed since then. More than 10 pages, for example, are dedicated to discuss whether AIDS will or not cause a significant dent in human growth rate.
Most Recent Customer Reviews
In population dynamics (a term inexplicably missing from Cohen's extensive index) the traditional ecological notion is that of carrying capacity. Read morePublished 3 months ago by Vaughan Pratt
Here is what I say in my own book (The Laws of Physics Are On My Side, 2013:57).
"For further definitions of carrying capacity, one can turn to Joel Cohen’s How Many... Read more
The most relevant question is "Support in what style?" The Earth could support vastly more people living like they do in rural India than in modern America. Read morePublished on February 28, 2013 by Graham H. Seibert
A very well researched work. It should be read by the leadership on the right and left. To say we are doomed is an understatement.Published on June 6, 2011 by Ken Counts
A lot of history of calculations for possible saturation point but not always the sustainable number. Has no actual conclusion or even a guess. Read morePublished on December 4, 2010 by jd soure
This is a textbook and it reads like one. However, it is full of well documented (and often frightening) information. Read morePublished on April 15, 2010 by R. Stan Soth
This is a highly technical and theoretical treatment with a heavy emphasis on quantitative analysis rather than social science or policy. Read morePublished on September 11, 2009 by James Bruner
""Surprisingly, in spite of the abundant data to the contrary, many people believe that human population grows exponentially. Read more