A ccording to the folk tales of Central Asia, centuries ago an adviser to a powerful king invented an intriguing game. It was played by moving
pieces on a board containing eight columns and eight rows of squares. The
king was so delighted with the game that he by Advertise"> offered to reward his adviser with
gold and jewels. The adviser declined, protesting that he was a humble man with
simple tastes. Rather than accept such a lavish reward, he asked that he be given
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✵a single grain of rice for the first square of his board game, twice for the second
square, twice that for the third, and so on, until each of the 64 squares had their
complement of rice. The king quickly agreed to what he believed was a modest
request. When the Master of the Royal Granary counted out the grains, the
numbers began small enough (1, 2, 4, 8, 16, 32, 64, …), but before long, he
realized the staggering numbers that would soon be involved. For the 64th
square alone, 9,223,372,036,854,775,808 grains would be needed to meet the
adviser’s request. That would amount to roughly 153 billion tons of rice, enough
to fill 31 million cargo ships full if each ship held approximately 5,000 tons
(Dörner 1996, 111). Of course, that would be merely the amount of rice on
the last square of the board game. The next-to-the-last square would take half
as much, only 4,611,686,018,427,387,904 grains, the square before it,
2,305,843,009,213,693,952 grains, and so on.
The story of the king’s adviser is a fable that reminds us of the consequences
of exponential growth. Under certain conditions, amazing configurations can
develop over time. Ever since the Reverend Thomas Malthus proposed in
1798 that when unchecked, population increases in a geometric ratio (e.g., 1 to
2, 2 to 4, 4 to 8) while subsistence increases in only an arithmetic ratio (1 to 2, 2
to 3, 3 to 4), demographers have speculated about the long-term consequences
of rapid population growth. Earth’s population at the beginning of the twentieth
century totaled 1.7 billion people; today it has reached 6.7 billion. Every two
years, it grows roughly by the size of Russia, with over 200,000 people added
to the world total every day. Will these kinds of increases in the world’s population continue in the decades ahead? If so, what impact would they have on the
planet’s carrying capacity—the earth’s ability to support and sustain life? Will
population growth outstrip by Advertise"> natural resources? Can enough food be produced to
feed the billions who will be born in the future? These concerns have attracted
the attention of various scholars and policy makers who are studying how current demographic and environmental trends may affect the global future.
The tragedy of the commons is a metaphor that highlights the potential
impact of human behavior on the planet’s resources and its delicately balanced
ecological systems. First articulated in 1833 by English political economist
William Foster Lloyd, the metaphor was later popularized by ecologist Garrett
Hardin. It depicts a medieval English village, where the village green was common
pasture on which all villagers could graze their cattle. Freedom of access to the
commons was a cherished value. Sharing the common grazing area worked well
as long as usage by individuals (and their cattle) didn’t reduce the land’s usefulness
to everyone else. Assuming the villagers were driven by the profit motive and no
laws existed to restrain their greed, herders had an incentive to increase their stock
tragedy of the commons a metaphor, widely
used to explain the impact
of human behavior on
ecological systems, that
explains how rational selfinterested behavior by
individuals may have a
destructive collective
impact.
carrying capacity the
maximum biomass that can
be supported by a given
territory.
364 C H A P T E R 14as much as possible. In the by Advertise"> short run, the addition of one more animal would
produce a personal gain whose feeding costs would be borne by everyone. But if
everyone increased their stock of cattle, in the long run the village green would be
destroyed by overgrazing. The lesson? “Ruin is the destination toward which all
men rush,” Hardin (1968) concluded, “each pursuing his own best interest.”
This chapter explores the impact of humanity on the natural environment
and how it will most likely affect the global future. The chapter opens with an
examination of prevailing trends in demography and ecology, and then considers
the ways that these trends interact, often creating global environmental problems
that can be exacerbated when, like in the tragedy of the commons metaphor,
self-interested actors pursue personal, short-run gains without anticipating the
side effects and long-term repercussions of their behavior.
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