Human Population Patterns 165- It took 130 years to reach 2 billion (in 1930), 30
years to reach 3 billion (in 1960), 15 years to reach 4
billion (in 1975), 12 years to reach 5 billion (in 1987),
12 years to reach 6 billion (in 1999), and 12 years to
reach 7 billion (in 2011). Population experts predict
that the population will level out during the 21st cen-
tury, possibly forming an S curve as observed in some
other species.
One of the first people to recognize that the
human population can’t increase indefinitely was
Thomas Malthus (1766–1834), a British economist. He
pointed out that human population growth is not al-
ways desirable—a view contrary to the beliefs of his day
and to those of many people even today. Noting that
human population can increase faster than its food
supply, he warned that the inevitable consequences
of population growth would be famine, disease, and
war. Since Malthus’s time, the human population has
increased from about 1 billion to 7 billion.
On the surface, it seems that Malthus was wrong.
Our population has grown dramatically because geo-
graphic expansion and scientific advances have allowed
food production to keep pace with population growth.
Malthus’s ideas may ultimately be proved correct, how-
ever, because we don’t know whether this increased
food production is sustainable. Have we achieved this
increase in food production at the environmental cost
of reducing the planet’s ability to meet the needs of
future populations? Many economists suggest that mar-
ket forces and future technologies will help us prevent
resource depletion such as soil degradation and over-
fishing in the ocean. But the truth is that we still do not
know if Malthus was wrong or right.
Our world population was 7 billion in late 2011, an
increase of about 95 million from 2010. This increase
was not due to a rise in the birth rate (b), although
high birth rates are a serious problem in many coun-
tries. In fact, the world birth rate has declined slightly
during the past 200 years. The population growth is
due instead to a dramatic decrease in the death rate
(d), which has occurred primarily because greater
food production, better medical care, and improve-
ments in water quality and sanitation practices have - Summarize the history of human population
growth. - Identify Thomas Malthus, relate his ideas on
human population growth, and explain why he
may or may not have been wrong. - Explain why it is impossible to precisely
determine how many people Earth can
support—that is, Earth’s carrying capacity
for humans.
N
ow that you have examined some of the
basic concepts of population ecology, let’s
apply those concepts to the human popula-
tion. Figure 7.6 shows the increase in
human population. Reexamine Figure 7.3 and com-
pare the two curves. The characteristic J curve of
exponential population growth shown in Figure 7.6 re-
flects the decreasing amount of time it has taken to add
each additional billion people to our numbers. It took
tens of thousands of years for the human population to
reach 1 billion, a milestone that took place around
Human Population Patterns
LEARNING OBJECTIVES
8000 6000 4000 2000 0 2000
BCE CE
Time (years)Human population (billions) 1234567
2011: 7 billionBlack Death Based on data from Population Reference Bureau.Õ>Ê««Õ>ÌÊ}ÀÜÌ ÊUÊ}ÕÀiÊÇ°ÈÊ
Compare this figure to Figure 7.5b. Do you think what happened
to the reindeer on the Pribilof Islands could happen to Earth’s
human population? Why or why not? (Black Death refers to a
devastating disease, probably bubonic plague, that decimated
Europe and Asia in the 14th century.)