By Joel E. Cohen, The New York Times, October 23, 2011
How many people can live fulfilling lives in harmony with other species? |
ONE week from
today, the United Nations estimates, the world’s population will reach seven
billion. Because censuses are infrequent and incomplete, no one
knows the precise date — the Census Bureau puts it somewhere next March — but there can be no
doubt that humanity is approaching a milestone.
The first billion people accumulated over a leisurely interval, from
the origins of humans hundreds of thousands of years ago to the early 1800s.
Adding the second took another 120 or so years. Then, in the last 50 years,
humanity more than doubled, surging from three billion in 1959 to four billion
in 1974, five billion in 1987 and six billion in 1998. This rate of population
increase has no historical precedent.
Can the earth support seven billion now, and the three billion people
who are expected to be added by the end of this century? Are the enormous
increases in households, cities, material consumption and waste compatible with
dignity, health, environmental quality and freedom from poverty?
For some in the West, the greatest challenge — because it is the least
visible — is to shake off, at last, the view that large and growing numbers of
people represent power and prosperity.
This view was fostered over millenniums, by the pronatalism of the
Hebrew Bible, the Roman Empire, the Roman Catholic Church and Arab thinkers like
Ibn Khaldun. Mercantilists of the 16th through the 18th centuries saw a growing
population as increasing national wealth: more workers, more consumers, more
soldiers. Enlarging the workforce depressed wages, increasing the economic
surplus available to the king. “The number of the people makes the wealth of
states,” said Frederick the Great.
In the late 19th and early 20th centuries, pronatalism acquired a
specious scientific aura from social Darwinism and eugenics. Even today, some
economists argue, incorrectly, that population growth is required for economic
growth and that Africa is underpopulated.
This view made some sense for societies subject to catastrophic
mortality from famines, plagues and wars. But it has outlived its usefulness
now that human consumption, and pollution, loom large across the earth.
Today, while many people reject the equation of human numbers with
power, it remains unpalatable, if not suicidal, for political leaders to admit
that the United States and Europe do not need growing populations to prosper
and be influential and that rich countries should reduce their rates of
unintended pregnancy and help poor countries do likewise. With the
globalization of work, the incentive for owners of capital today to ignore or
not address rapid growth in the numbers of poor people remains as it was for
the kings of yore: lower wages for workers at any level of skill offer a bigger
economic surplus to be captured.
But just as pronatalism is unjustified, so are the dire — and
discredited — prophecies of Thomas Malthus and his followers, who believed that
soaring populations must lead to mass starvation.
In fact, the world is physically capable of feeding, sheltering and
enriching many more people in the short term. Between 1820, at the dawn of the
industrial age, and 2008, when the world economy entered recession, economic
output per person increased elevenfold.
Life expectancy tripled in the last few thousand years, to a global
average of nearly 70 years. The average number of children per woman fell
worldwide to about 2.5 now from 5 in 1950. The world’s population is growing at
1.1 percent per year, half the peak rate in
the 1960s. The slowing growth rate enables families and societies to focus on
the well-being of their children rather than the quantity.
Nearly two-thirds of women under 50 who are married or in a union use some form of contraception, which saves
the lives of mothers who would otherwise die in childbirth and avoids millions
of abortions each year — an achievement that people who oppose and people who
support the availability of legal abortions can both celebrate.
But there is plenty of bad news, too. Nearly half the world lives on
$2 a day, or less. In China, the figure is 36 percent; in India, 76 percent.
More than 800 million people live in slums. A similar number, mostly women, are illiterate.
Some 850 million to 925 million people experience food insecurity
or chronic undernourishment. In much of Africa and South Asia, more than half
the children are stunted (of low height for their age) as a result of chronic
hunger. While the world produced 2.3 billion metric tons of cereal grains in
2009-10 — enough calories to sustain 9 to 11 billion people — only 46 percent
of the grain went into human mouths. Domestic animals got 34 percent of the
crop, and 19 percent went to industrial uses like biofuels, starches and
plastics.
Of the 208 million pregnancies in 2008, about 86
million were unintended, and they resulted in 33 million unplanned births. And
unintended births are not the whole problem. Contraceptives have been free
since 2002 in Niger, where the total fertility rate — more than seven
children per woman in mid-2010 — was the world’s highest. Women in Niger marry
at a median age of 15.5, and married women and men reported in 2006 that they
wanted an average of 8.8 and 12.6 children, respectively.
Human demands on the earth have grown enormously, though the
atmosphere, the oceans and the continents are no bigger now than they were when
humans evolved. Already, more than a billion people live without an adequate,
renewable supply of fresh water.
About two-thirds of
fresh water is used for agriculture. Over the coming half
century, as incomes rise, people will try to buy agricultural products that
require more water. Cities and industries will demand more than three times as
much water in developing countries. Watershed managers will increasingly want
to limit water diversion from rivers to maintain flood plains, permit fish to
migrate, recycle organic matter and maintain water quality.
Water shortages are projected to be significant in northern Africa,
India, China, parts of Europe, eastern Australia, the western United States and
elsewhere. Climate changes will increase the water available for agriculture in
North America and Asia but decrease it in Africa, Latin America and the
Caribbean. Similar stories could be told about land, overfishing and carbon and
nitrogen emissions to the atmosphere.
Where is this taking us? The coming half century will see huge shifts
in the geopolitical balance of numbers, further declines in the number of
children per woman, smaller but more numerous households, an increasingly elderly
population, and growing and more numerous cities.
The United Nations Population Division anticipates
8 billion people by 2025, 9 billion by 2043 and 10 billion by 2083. India will
have more people than China shortly after 2020, and sub-Saharan Africa will
have more people than India before 2040.
In 1950, there were nearly three times as many Europeans as
sub-Saharan Africans. By 2010, there were 16 percent more sub-Saharan Africans
than Europeans. By 2100, according to the Population Division, there will be
nearly five sub-Saharan Africans for every European.
In some ways, the growth in the numbers of people matters less than
the growth in the numbers of households. If each household has its own
refrigerator, air-conditioner, TV and car, the average energy demand for a
given number of people goes up as the average number of people in a household
goes down.
The urban population of developing countries is expected to grow by a million people every five days through at
least 2030, while the rural population falls. Many cities will eat into prime
agricultural land unless they grow in density, not extent. And nearly half of urban population growth by 2015 will occur in cities of
fewer than half a million people.
The coming revolution in aging is well under way in the more developed
countries. It will go global in the next half century. In 1950, for each person
65 and older, there were more than six children under 15. By 2070, elderly
people will outnumber children under 15, and there will be only three people of
working age (15 to 64) for every two people under 15 or 65 and older. Pressures
to extend the “working age” beyond 65 will grow more intense.
Is economic development the best contraception? Or is voluntary
contraception the best form of development? Does the world need a bigger pie
(more productive technologies) or fewer forks (slower population growth through
voluntary contraception) or better manners (fewer inequities, less violence and
corruption, freer trade and mobility, more rule of law, less material-intensive
consumption)? Or is education of better quality and greater availability a key
ingredient of all other strategies?
All these approaches have value. However much we would like one, there
is no panacea, though some priorities are clear: voluntary contraception and
support services, universal primary and secondary education, and food for
pregnant and lactating mothers and children under 5.
These priorities are mutually reinforcing, and they are affordable.
Providing modern family planning methods to all people with unmet needs would
cost about $6.7 billion a year, slightly less than the $6.9 billion Americans are expected to spend
for Halloween this year. By one estimate, achieving universal primary and secondary education by
2015 would cost anywhere from $35 billion to $70 billion in additional spending
per year.
IF we spend our wealth — our material, environmental, human and
financial capital — faster than we increase it by savings and investment, we
will shift the costs of the prosperity that some enjoy today onto future
generations. The mismatch between the short-term incentives that guide our
political and economic institutions and even our families, on one hand, and our
long-term aspirations, on the other, is severe.
We must increase the probability that every child born will be wanted
and well cared for and have decent prospects for a good life. We must conserve
more, and more wisely use, the energy, water, land, materials and biological
diversity with which we are blessed.
Henceforth we need to measure our growth in prosperity: not by the
sheer number of people who inhabit the earth, and not by flawed measurements
like G.D.P., but by how well we satisfy basic human needs; by how well we
foster dignity, creativity, community and cooperation; by how well we care for
our biological and physical environment, our only home.
Joel E. Cohen, a mathematical biologist and the head of the Laboratory of Populations at Rockefeller University and Columbia University, is the author of “How Many People Can the Earth Support?”
Joel E. Cohen, a mathematical biologist and the head of the Laboratory of Populations at Rockefeller University and Columbia University, is the author of “How Many People Can the Earth Support?”
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