The book by Joel E. Cohen, “How Many People Can the Earth Support?” in Appendix 3 (p.402-18) lists many authors’ answers to that unanswerable question. Perhaps a better question would be, looking back from the distant future after humanity has passed on into oblivion, “What was the maximum population of humans the Earth ever achieved?” Ultimately, that will be a very specific number which in fact may be known at some time in the not to distant future by people now living, whereas the book’s title has a huge number of imponderable variables built into its question which can never be answered even after the fact. It was a poor question from a scientific point of view. Below is a list of various authors attempts to put a number to that question. Numbers are in billions. The current world population is approximately 6.8 billion.
|Billion ~||Billion ~ 13.4||Leeuwenhoek||1679||First known estimate|
|5.2||Edward M. East||1924|
|2.~||Pearl & Reed||1924|
|5.7||Warren D. Smith||1935|
|2.6||Pearl & Gould||1936|
|.9||2.8||Pearson & Harper||1945|
|6.-||10~||C. Galton Darwin||1952|
|10×10 raised 18||Fremlin||1964||Heat dissipation limit|
|79.-||1,022.-||De Wit||1967||Total usage|
|40.-||60.-||Austin & Brewer||1971|
|0.5||1.2||Ehrlich||1971||Permanent & stable|
|100.~||Lieth & Blaxter||1973|
|5.~||7.~||Whittaker & Likens||1975|
|17||Eyre & Blaxter||1978|
|6.1||Ferrell, Sander, Vo||1984|
|22||Calvin & Hudson||1986|
|23.8||Tuckwell & Koziol||1992|
|much less 5.5||Ehrlich||1993|
|11.6||Daily & Ehrlich||1992|
|2.0||Pimentel||1999||At American style|
As you can see for yourself there is little agreement among these projections and that is why the question is flawed. If each of these researchers was asked “What is the maximum number the population the Earth would reach before retreating,” there would probably be a number much nearer Leeuwenhoek’s first prediction of 13.4 billion made back in 1697. He may have been looking through the first microscope but surely he had a reasonably clear distant vision also.
- See also:
- Population, Sustainability by Daily & Paul Ehrlich
- How Many People Should the Earth Support? by Ross McCluney
- Wikipedia article on – Overpopulation
- World Prout Assembly gives a generalized smoothed version.
- The chart above seems to indicate that the population will smoothly top out in 2040 and then smoothly drop back to a more sustainable number. This scenario would be possible if every person on the planet was reasonable but my modest experience has led to believe the exact opposite it closer to the truth.
Probaway’s Doomdsay chart above doesn’t predict an exact day for Doomsday or an exact population when that day comes but it does imply that the Earth’s population will be very near its maximum when that day does arrive.
Pick a number, any number at all from 0 to 1,000,000,000,000,000,000 for the maximum number that the Earth will support and there will be a scholarly supporter for that number. This is especially true if you fund a univiersity chair for that scholar.