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Re: Yuri receives hypocrite of the week award (was Re: Ecological Economics and Entropy)





John McCarthy <jmc@Steam.stanford.edu> wrote in article 
>  
> Yes, but what is the actual numerical argument about how fresh water
supplies
> limit population?
> -- 
> John McCarthy, Computer Science Department, Stanford, CA 94305
> http://www-formal.stanford.edu/jmc/progress/
> During the last years of the Second Millenium, the Earthmen complained
> a lot.


Well you can set a practical limit by finding out the total amount of fresh
water on the earth and divide by the average water usage per person
(including that used for growing crops and raising livestock).  I don't
have those numbers handy (or even know where to find them).  Of course
you'll offer to desalinate the oceans--but one of my points to jw was that
this takes ENERGY which we 'ain't' got.  However, if you want to get really
'crazy' take the total amount of water on the earth--about 1.5x10^21 kg
(almost all in the oceans) and divide by 50 kg the approximate amount of
water in an adult person.  You get about 3x10^19 people.  jw would be
thrilled, this is 30 million, trillion people.  Of course that ties up ALL
the earth's water, none left for crops, bathing, drinking, any other
biological life, etc.  Each person would have to carefully recycle every
gram--but of course this is ridiculous.  It does, however set an absolute
limit, although I suspect that the amount of other elements necessary for
human life and their abundance on earth would set an even lower limit--any
biologists out there with that number?

Of course each of these 30 million,trillion people get a whole 17 square
millimeters of the earth's surface for themselves!  We can use the whole
earth for this since all the ocean's waters are tied up in people.

Even at jw's trillions, we have a problem with space.  At 1 trillion,
that's only 100 square meters per person (of dry land).  Obviously you have
to build up, down, or go undersea to spread this trillion out, but any of
that takes HUGE amounts of energy--for construction, heating, cooling,
sanitation, lighting, etc., etc.  Even 1 trillion is a ridiculous figure
for an earth population, and the technological and energy constraints on
establishing large colonies in this solar system are also out of the
question.  But, for jw and those who decry any kind of population control,
at a 1% annual population growth we WOULD hit a trillion in only a little
over 500 years from now!  

If anyone has fresh water stats I also would like to see them.  What we
need is:

Total fresh water supply:  could probably use average rainfall over land
time area.

Average water use per person: (including water needed to produce food)

Energy cost per unit to desalinate salt water:

>From  a Biologist or BioChemist a figure of rare elements necessary for
human life.
The amount per person and the total estimated amount (near the surface) of
the earth.


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