Newsgroups: sci.environment

/ hpindda:sci.environment / steinly@topaz.ucsc.edu (Steinn Sigurdsson) /  7:16 am  Mar 31, 1992 /
In article <40911698@hpindda.cup.hp.com> alanm@hpindda.cup.hp.com (Alan McGowen) writes:

      In article <STEINLY.92Mar25110713@topaz.ucsc.edu> steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes:
>   dieback. I think that a noncatastrophic reduction of human population
>   by 90% *could* be achieved in a 100 -- 200 year time frame, say 150
>   years.
>
>Precisely the time frame I was discussing. 150 years is two life
>expectancies, to get 90% reduction in that time you either must reduce
>life expectancy or produce <<1 child per person. Daniel Moscny
>addressed that problem.

Back of envelope. I was using a mental estimate of 150 years = 5 
generations, birth rate = 1 per woman. Without considering age 
structure, this is W(mean fitness) = 0.5, (0.5)^5 = 0.03. Even with 
reasonable mortality and fertility schedules added in, this will not be 
far above 0.1, and many of the women would be above the age of 
reproduction.  We could even achieve a stable age structure by 2200, 
though that isn't very important as far as the extinction crisis is 
concerned; we could certainly reach a 90% reduction by 2200, or even greater
reduction if we stuck at 0.5 for 200 years (0.5^7 = 0.007. From a base
of 5.5E09 that gives about 43 million after the age distribution becomes
flat! This is an order of magnitude smaller than I am advocating.)

If we need to, we can work up a more accurate timetable including explicit 
assumptions about mortalities and fertilities at different ages, but 
I think I've made it clear that the 90% reduction *could* be done easily 
within 200 years by spending a long enough period near one child/couple.
Not << 1 child per person, just about 0.5. As Irv Chidsey points out,
you get a reduction to about 12% by sticking at 0.5 for 3 generations,
and a flat age structure by shifting to 1.0 for another three, which
gets you to about 200 years. 

Of course I don't think that we are actually going to get W = 0.5 right
away -- hence the stars around *could* above . We have to begin moving in 
this direction as quickly as we can, however. Perhaps we could reach W = 0.5
in the overdeveloped world in 30 years, and W = 1.0 -- replacement 
fertility -- in the underdeveloped. Perhaps a slightly slower rate of 
decrease, W = 0.6 or 0.7 should be the target if we can free up land and 
restore ecosystems faster by relocating people (or inducing people to 
relocate by making some places more desirable to live than others). 200 
years to 10% is not an inflexible, sacred goal, in any case: the object 
is to reduce human impact on ecosystems as quickly as possible, compatibly
with maintaining some form of (increasingly sustainable) technological 
civilization. It is more important to reduce population growth as much 
as possible *now* than to reach 10% by 2200 -- the lower the population 
peak, the softer the entire "human shock" to the biosphere will be. It
would be *much* better to peak at 7-8 billion (unlikely) and reach the 10% 
goal at 2300 than to peak at 15 billion (catastrophic, but very possible)
and reach the 10% goal at 2200 (or even sooner due to dieback).

>
>   The transition from a growth economy to a steady-state economy is a
>   nontrivial problem, one which economists should be investigating in
>   detail. 
>
>Indeed. I wouldn't hold my breath waiting for success either!

The prepcon-3 document (for the upcoming "Earth Summit" in Rio) 
on sustainable development calls for research on the transition
to steady-state economies within its funding package. There is 
a very good chance that the funding for the sustainable development
research will all be approved at Rio, and actually made available by
the signatories. So there will be research grants in this area within
a year or two.

>	Kicking the growth habit is likely to be difficult, even 
>   though we know that the equilibrium economy will be intrinsically 
>   healthier.  
>
>We _know_ this? Will you invite your Usenet pals to the ceremony
>when you get you Nobel medal?

Maybe they'll give it to Herman Daly: he deserves it. Anyone with a 
basic grasp of biological science can see that an economy premissed 
on growth is guaranteed to be a temporary affair, one way or another. 
Daly seems to have that basic grasp; most other economists do not.
Growth always eventually saturates -- it's another guise of the principle 
of tolerance at work. If you want health, seek prudent, optimal 
equilibrium, not the enforced limitation to growth of the yeast who 
die in the wine vat in their own alcoholic waste, or of disease-infested
animals who have exceeded their carrying capacity. An economy based on
growth is healthy only until the first signs of limitation show up -- and
these are all around us now -- thereafter health is maintained at optimal
equilibrium or it is not maintained very well at all. Seeking growth
past the optimum is the road to poor health, and we are already some
distance down it.

Conclusion: we *know* that the equilibrium economy will be intrinically 
healthier. Unless we are totally ignorant of biological science, of 
course, as technocrats and creationists invariably are.

--------
Alan McGowen

"If we breed like rabbits, in the end we shall die like rabbits."

--Rachel Carson.