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From: carnes@gargoyle.UUCP (Richard Carnes)
Newsgroups: net.politics,net.sci
Subject: Re: Nuclear power: Petr Beckmann
Message-ID: <541@gargoyle.UUCP>
Date: Wed, 30-Jul-86 15:50:37 EDT
Article-I.D.: gargoyle.541
Posted: Wed Jul 30 15:50:37 1986
Date-Received: Fri, 1-Aug-86 21:03:50 EDT
References: <460@dg_rtp.UUCP> <538@gargoyle.UUCP>
Reply-To: carnes@gargoyle.UUCP (Richard Carnes)
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Our newsfeed has been having manic-depressive episodes lately, so I
am reposting an article.

Congrats to everyone who wrote to explain Paul Ehrlich's alleged
"confusion" concerning an elementary fact about fertility that he has
no doubt been teaching to undergraduates for 25 years in the first
week of "Introduction to Population Biology" -- you have confirmed my
estimate of the net's level of brilliance.  Presumably the same
people, when they read the end of this article, will write to explain
that the eminent ecologist is unaware that CO2 is "absorbed" in
photosynthesis; I assume they would not hesitate, in conversation
with S. J. Gould, to explain to him that dinosaurs were not
contemporaneous with cave men, or point out to Carl Sagan that there
are many more stars than you can see with the naked eye, or explain
to Richard Feynman that protons carry a positive charge.  Sheesh.

I will not have the time or stomach to read the netnews for a long
while at least, so if you want to argue with me please send email.
Following is the text of the reposted article:

>>[Paul & Anne Ehrlich]
>>Beckmann's chapter on coal contains a variety of confused assertions,
>>one of which is that "in the United States, for example, the
>>fertility rate has dropped below the `Zero Population Growth' level,
>>but its population is still expanding." ...
>
>What is confused about this?  Seems straightforward to me.
>In fact, it seems likely that the Ehrlichs are confused here.

"ZPG fertility rate" is not an accepted synonym for "replacement
reproduction", which is apparently what Beckmann is referring to:
that level of the total fertility rate which, sustained for about one
life expectancy, will result in the leveling off of population growth
to ZPG, assuming no net immigration or changes in age-specific vital
rates.  "The TOTAL FERTILITY RATE is the average number of children
each woman would bear during her lifetime if age-specific fertility
remained constant, and a total fertility rate of 2.1 is roughly equal
to an NRR [net reproductive rate] of 1 where typical developed
country death rates prevail."  [P. Ehrlich, A. Ehrlich, and J.P.
Holdren, *Ecoscience*, 2nd ed., p. 218].  In the US, the total
fertility rate has been under the replacement level of 2.1 since
about 1972, at least until about 1983, the last year for which I have
found data.  

Nit-picking?  Perhaps, but the quote from Beckmann is found in a book
(*The Resourceful Earth*) that brags about its sophisticated approach
to projections of population and resource phenomena.  Speaking as
former president of ZPG, Paul Ehrlich writes:

  ...these organizations [ZPG and Friends of the Earth] feel that the
  U.S. population should be stabilized, and they rightly view current
  immigration practices as destabilizing.  They believe that there
  should be a national population policy, spelled out and written down,
  and they realize that there can be no coherent population policy that
  does not include an immigration policy.  Eventually, the number of
  people who enter the United States must be balanced by the number
  leaving or by a reduction in fertility.  The sooner this is achieved,
  the better.  The population of the United States has already exceeded
  the optimum if not the maximum for maintaining the kind of life
  Americans expect.  [P. Ehrlich, A. Ehrlich, and L. Bilderback, *The
  Golden Door:  International Migration, Mexico, and the United
  States*, pp. 344-45.]

So it is not clear what "ZPG fertility rate" should mean, if
anything, although it is clear what Beckmann intends by the phrase.
In *Ecoscience*, Ehrlich et al. explain some basic concepts of
demography:

  If age-specific vital rates (birth and death) remain constant, the
  age composition of a population eventually becomes STABLE, a
  situation in which the proportion of people in each age class does
  not change through time.  A population with a stable age composition
  can be growing, shrinking, or constant in size....
  
  When a population is constant in size, demographers refer to it as
  STATIONARY.  Colloquially, one says that zero population growth has
  been achieved....
  
  The NRR [net reproductive rate] of a human population is the ratio of
  the number of women in one generation to that in the next.  It is
  calculated by applying the age-specific birth and death rates of the
  population at a given time to a hypothetical group of 1000 newborn
  female babies, determining how many live female babies those females
  would themselves produce, and dividing that number by 1000. ...
  
  The drop in American fertility to below replacement level between
  1972 and 1975 was popularly interpreted to mean that ZPG had been
  achieved in the United States.  But growth certainly had not
  stopped.... 
  
  Demographer Thomas Frejka, using 1965 as a base year, showed what
  could happen to the United States population under a variety of
  assumption.  For instance, instant ZPG could be achieved only by
  reducing the NRR to slightly below 0.6, with an average of about 1.2
  children per family, between 1965 and 1985. ... After that, in order
  to hold the population size constant, the crude birth rate and NRR
  would have to oscillate wildly above and below the eventual
  equilibrium values for several centuries.  The age composition would
  correspondingly change violently, undoubtedly having a variety of
  serious social consequences.  
  
  [These problems] could be avoided by maintaining the 1975 level of
  fertility (slightly below replacement).  This would produce further
  growth, but at a slackening rate.  Disregarding immigration, growth
  would end in about fifty years with a peak population of about 252
  million, and then there would be a slow decline.  Accepting some
  further growth followed by a period of negative population growth,
  rather than attempting to hold the population precisely at ZPG, would
  seem to be much less disruptive.  And ... there are powerful
  arguments for reducing the size of the United States population well
  below its *present* level.... [Ehrlich et al., *Ecoscience*, pp.
  208-14]

Now here are two more confused assertions of Beckmann, according to
the Ehrlichs:

  [Beckmann] also says that deforestation in the Third World could play
  a significant role in reducing the "absorption" of carbon dioxide
  produced by coal burning ("absorption" into what?), and that "high
  labor intensity and troublesome handling" will be "far more decisive"
  in affecting coal use than will be all its environmental problems
  combined.

Richard Carnes