X-Message-Number: 23778
Date: Tue, 30 Mar 2004 11:12:34 -0500 (EST)
From: Charles Platt <>
Subject: population
References: <>

Peter Merel wrote:

> You're also quite right about the carrying capacity of the
> planet. Without the resource synthesis technologies
> promised by the development of molecular nanotechnology and
> related new tools, it's about 2-3 billion people. Yes, only
> half the number alive today. That's going to cause us all a
> little trouble by and by.

Hm, some citations would be nice, Peter!

The most exhaustive study of this topic that I have been able
to find, after a great deal of searching, is "How Many People
Can the Earth Support?" by Joel E. Cohen, praised as "The
definitive work on the global population problem" by no less
than Edward O. Wilson. In this lengthy book Cohen cites a
variety of reasonably plausible sources placing the
sustainable global population limit anywhere from 1 billion
to 1,000 billion. This alone is enough to tell us that this
is a field full of speculation masquerading as serious study.
The median of all estimates was between 8 and 12 billion (not
a precise number, because many "experts" in this field
suggest a probable range rather than a specific figure--again
indicating uncertainty).

Cohen himself figures the population limit by looking at
resources for which there is no substitute, and #1 on his
list is water for agriculture. If about 9000 cubic kilometers
of fresh water are globally available per year, "the optimal
population to be supported by irrigated agriculture is below
five billion people."

Of course even this estimate, derived by someone who has
spent a large part of his life studying population and
evaluating statistics, could be invalidated very quickly if a
new energy source (for instance) enabled vast desalinization

Overall, no one knows what the carrying capacity of the
planet is now, and no one can possibly state what it will be
in the future.

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