World Should Prepare for 11 Billion or More People
(not 9)
Contrary to previous estimates, the number of people on the planet now seems
unlikely to stabilize this century
Scientific American Sep 19, 2014 |By
David Biello
In the 1970s, the world reached peak
child—the highest rate of human population growth. Since then, countries in
Asia, the Americas, Australia and Europe have all seen birth rates decline
dramatically and in Africa, the number of children in families has dropped
from an average of more than six to around four. But that decline in Africa
is slower than the birth rate drops in other parts of the world. The
persistence of that relatively high birth rate stems from a wide range of
factors, including cultural influences, economics, and a lack of access to
birth control or family planning. And there are enough children in Africa
now that some demographers and statisticians are predicting that
human population growth will not actually flatten in the 21st century,
as some experts had foretold.
Other recent estimates have forecast a
leveling out of
human population growth by mid-century, from a current 7.2 billion
people to around 10 billion by 2050. But those projections counted on
families in Africa reducing the number of children they have at roughly the
same rate that fertility declined in Asia and Latin America in previous
decades. Instead, women are still having more
children in many African countries and the rate of fertility decline has
slowed—or even reversed—in some African countries in the last 15 years.
"This has a compounding effect on population over time, because
higher fertility means more children for the current population, and hence
more grandchildren and so on," explains statistician Adrian Raftery of the
University of Washington, part of the team that conducted the new analysis.
"We project a large increase in the population of
Africa, from the current 1 billion to 4.2 billion in 2100," he
notes. Raftery and his colleagues detail their findings in a
report published online September 18 in
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How fast and how far fertility in Africa
falls—or doesn’t—will determine the fate of human population growth or decline
this century. At current rates, the African continent would likely become as
densely populated as China today. As a result, the "world population is likely
to
continue growing for the rest of the century," Raftery says, although fast
population growth in Africa may also lead to the kind of shortages of food,
water and other resources that can reduce population growth.
"The fast growth of the world population will be over in the second part of this
century," says international health researcher Hans Rosling of the Karolinska
Institute in Stockholm, who expects the world should
prepare for at least 11 billion people. Still,
"the total population may continue to grow, but at a much slower rate, or it may
even start to slowly decline after 2050," he adds.
The new analysis is part of a project to develop better methods for forecasting
human population size—one of the
leading factors influencing the global economy, environment and human
health. Prior methods relied on arbitrary assumptions, such as adding or
subtracting half a child to deliver high and low population estimates. This new
estimate derives from
Bayesian statistics, in which different outcomes are assigned different
probabilities based on what has already occurred.
The cancellation of funding for family planning programs
in the U.S. in the early years of the 21st century may bear some of the blame
for the stalled population growth slowdown in Africa. The Bush administration
poured billions of dollars into the fight against AIDS but also required that
none of that money be used to provide contraceptives—a policy since
reversed by the Obama administration. According to United Nations surveys, at
least 25 percent of women in sub-Saharan African countries want to stop or delay
having children but
lack
access to contraception. "This is largely unchanged
over the last 20 years," Raftery notes.
Ultimately, empowering women by
educating
girls may do more to aid family planning than even providing money for
contraceptives does. The countries with the highest fertility rates also have
high rates of girls failing to receive an education. Educated women are far more
likely to have
access to contraception, among other benefits, including faster economic
growth for their nation. In Ghana, for example, uneducated women have an average
of 5.7 children, whereas women with some education have 3.2 and women with a
college education have just 1.5 kids. Says Rosling: "It is a shame that almost
half of the women in Africa that want to use
contraceptives still, to this day, do not have access to them."
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