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 projects. 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. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=23778