[Paleopsych] Reason: Make Mine Malthus!: Overpopulation panic's eternal return
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Mon Aug 2 22:03:23 UTC 2004
Make Mine Malthus!: Overpopulation panic's eternal return
The world has never been overpopulated with humans in any meaningful
sense. It seems, though, that it is overpopulated with theoretical
fears of overpopulation.
The appeal of the overpopulation myth is obvious--who doesn't love a
simple, easily graspable idea that seems to explain a great deal? One
such idea is the central biological insight that all animals aim to
turn food into offspring. When a species' food increases, then its
population grows as well; and when the food supply declines, so too do
its numbers. This applies to everything from paramecia to parakeets.
Since humans are also animals that reproduce, biologists have extended
that insight to us as well. This is the source of the overpopulation
fears that have haunted learned experts from Thomas Robert Malthus
200 years ago to Paul Ehrlich today.
An extensive literature critiques the concept of human
overpopulation. But it's apparently an idea whose time comes again,
and again, and again, in all sorts of strange places. For instance,
the 1990s saw a bad novelization of the concept in Ishmael, in
which a telepathic gorilla recycles Malthusianism.
The latest iteration of this two-century-old idea comes from Duke
University consultant Russell Hopfenberg, in an article called
"Human Carrying Capacity Is Determined by Food Availability", in
the November 2003 issue of the journal Population and Environment.
Hopfenberg writes, "[T]he problem of human population growth can be
feasibly addressed only if it is recognized that increases in the
population of the human species, like increases in the population of
all other species, is a function of increases in food availability."
Hopfenberg backs his argument by showing that global food supplies and
human numbers both rise from 1960 to 2000. In 2001, Hopfenberg,
writing with Cornell University ecologist David Pimentel in
Environment, Development and Sustainability, further asserts that
"if food production continues to increase, the world population is
projected to increase to 12 billion in the next 50 years (based on
current growth rates)." Hopfenberg's solution to skyrocketing human
numbers is simple: "Cap the increases in food production and thereby
halt the increases in population by means of a reduced birth rate."
So has the Malthusian case finally been proven? No. Hopfenberg's
analysis makes the mistake of considering only global numbers. This
hides a great deal of information. If we look on the regional level we
see a very different picture than one of a relentlessly rising tide of
human babies. Fertility does not correlate with food availability.
The countries with greatest access to food are, in fact, the countries
with the lowest fertility rates. As the United Nations reports, 14
developed countries have fertility rates lower than 1.3 children per
woman. (Replacement fertility is 2.1 children per woman.) The
fertility rates in practically all developed countries are below the
replacement rate. Clearly, food availability does not mean more
children. More generally, as food security has increased around the
world, instead of increasing as Hopfenberg's theory would suggest,
global average fertility rates have dropped from 6 children per woman
in 1960 to 2.6 today. And the rates continue to plummet. Sadly, in
Africa, which has the highest current fertility rates, food production
per capita has been declining for nearly 30 years.
If food availability really determined human reproductive capacity,
Illinois farmers should have the highest fertility rate in the world.
Instead, they have one of the lowest. Hopfenberg would reply that
excess food produced in North America and Europe fuels population
growth in the rest of the world. In some sense that is trivially true,
but the strictly biological model that he says applies to people does
not account for such phenomena. For example, deer in Virginia don't
sacrifice their chances to produce fawns and ship their food to deer
in Arkansas, nor do sparrows in New York forego nesting in order to
supply food to Floridian sparrows. Individuals, not populations,
The notion that capping food supplies will halt population growth is
also trivially true, but not by the gentle means which Hopfenberg and
Pimentel suggest, e.g., reducing human birth rates. Food shortages no
doubt reduce fertility, but they also shrink population much more
quickly by simple starvation.
Finally, Hopfenberg and Pimentel's projection that world population
will reach 12 billion by 2050 is off. They simply extrapolate current
levels of fertility, yet as we've seen, fertility rates are rapidly
declining. The 2002 revision of the United Nations' World
Population Prospects' median variant trend projects a world population
of 8.9 billion by 2050. Given the rapidly falling global fertility
rates, the low variant trend is more likely--and that projects a world
population topping out at 7.5 billion by 2040, then beginning to
decline. Perhaps Malthusianism will finally decline along with
Ronald Bailey is Reason's science correspondent. His new book,
Liberation Biology: A Moral and Scientific Defense of the Biotech
Revolution will be published in early 2005.
10. mailto:rbailey at reason.com
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