From: tobis@meteor.wisc.edu (Michael Tobis)
Newsgroups: sci.environment
Subject: Re: population load question
Date: 5 Sep 92 20:54:54 GMT
Organization: University of Wisconsin, Meteorology and Space Science

In article <92Sep01.223316.26181@acs.ucalgary.ca> edstrom@Elmer.hsc.ucalgary.ca (John Edstrom) writes:
>Its a broad question but what are the current estimates of the
>carrying capacity of the earth for humans?  Somebody told me it around
>2 billion.

It's an ill-defined question as it stands. Do you expect energy supplies
to be limited or unlimited? Do you expect wild environments to be protected
or destroyed? Do you expect people to be affluent, barely comfortable, or
desperate? Do you believe that raw materials will be supplied from space
or not? (I think the last point is moot, as in a steady state earth will
not have much to offer extraterrestrially based people in trade unless
the natural environment is preserved. However, others may argue.)

I think that if one specifies a rough balance between speciation and
extinction, current levels of population, and current levels of affluence
and impact, the answer is clearly less than the current population.

To answer the question in a way that is more logical than intuitive requires
deciding, at least for argument's sake, the answers to the above questions,
and then deciding what the limiting process would be.

So let me rephrase the question: assume that the world lives well, with
an affluence comparable to, say, Connecticut. Assume no major technological
brieakthroughs or changes in life style, except that energy remains
available at current prices. Assume that there is no net loss of wilderness
area, and less than 10% loss of remaining species. WHAT IS THE LIMITING
PROCESS on sustained (steady state) human population?

Some readers will take this scenario to be ridiculously pessimistic. Others
will take it to be ridiculously optimistic. Never mind that. In order to get
a number, we need a scenario, and this one seems as good as any.

Any takers? What limits human population with land use, and
technology fixed at current levels, and affluence at the high end of
existing societies' conditions?

I think it is land use. I do not know much about agriculture, and I
understand there is some controversy about the sustainability of modern
practices. However, given the vast areas around here dedicated to the prolific
production of low-value animal feed, one suspects that the existing
agricultural land could sustain at least ten times the existing population.

Then the question of where to put them arises. If they all live a Connecticut
lifestyle, their endless suburbs will take up a lot of room. Since we
specified no loss of wildlands, a tradeoff occurs.

We have observed that the world's population could cover Texas at a
population density of Queens, NY, an observation I find not particularly
reassuring. Let's consider the population density of Connecticut instead.
The population density of Connecticut is 670/sq.mi. (1980), so at that
density, the current 5,000,000,000 would use up 7,470,000 sq.mi., about
twice the total area of the US, probably comparable to all the arable land
on earth. Well, alright, but we'll put them in the deserts, you say.

Assuming the water problems could be worked out, you would still be violating
the assumption of no additional impact on wilderness. Accordingly, if we
assume that a suburban North American lifestyle is a reasonable aspiration
for everyone, the world is already overpopulated, even if we all become
vegetarians.

If, however, you don't give a damn about wilderness, and believe life
is sustainable without it, then 50,000,000,000 is probably sustainable
at current technology levels as far as land goes, and then you need to
check on water supplies. Tofu balls anyone?

mt