Human Population
Chapter Objectives
This chapter will help students:
Assess the scope of human population growth
Evaluate how human population, affluence, and technology affect the
environment
Explain and apply the fundamentals of demography
Outline and assess the concept of demographic transition
Describe how wealth and poverty, the status of women, and family planning
programs affect population growth
Characterize the dimensions of the HIV/AIDS epidemic
Lecture Outline
I. Central Case: One-Child Policy
A. The People’s Republic of China is the world’s most populous nation,
home to one-fifth of the 6.5 billion people living on Earth at the start
of 2006.
B. Under Mao Zedong’s leadership, improved food production and
distribution and better medical care allowed China’s population to
swell, causing environmental problems.
C. The government instituted a population-control program in the 1970s.
1. The program started with education and outreach efforts
encouraging people to marry later and have fewer children, and
increasing the accessibility of contraceptives and abortion.
2. In 1979 the government decided to institute a system of rewards
and punishments, enforcing a one-child limit per family.
3. In 1984, the policy was relaxed, exempting rural areas and certain
minorities, thus minimizing opposition.
D. China’s growth rate is down to 0.6%; however, there have been
unintended consequences of the program, such as widespread killing
of female infants and an unbalanced sex ratio.
II. Human Population Growth: Baby 6 Billion and Beyond
A. The human population is growing nearly as fast as ever.
1. The human population has doubled since 1964. There are
approximately 6.7 billion humans living on the planet today.
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2. Since 1975 the world’s population has added one billion humans
every 12 years.
3. Most of human population growth is occurring in developing
countries where economic hardships exist and the governments are
ill-equipped to deal with increasing citizens requiring services.
B. Is population growth really a “problem”?
1. Our ongoing burst of population growth has resulted from
technological innovations, improved sanitation, better medical
care, increased agricultural output, and other factors that have led
to a decline in death rates, particularly a drop in infant mortality.
2. There are many people today who deny that population growth is
a problem.
3. Under the Cornucopian view, resource depletion as a consequence
of greater numbers of people is not a problem if new resources
can be found to replace the depleted resources.
4. Environmental scientists argue that not all resources are
replaceable by others once they are depleted, and that few
resources are actually created by humans.
5. Even if resource substitution could enable indefinite population
growth, could we maintain the quality of life that we would desire,
or would our descendants have less space, less food, and less
material wealth than the average person does today?
6. Many governments have found it difficult to let go of the notion
that population growth increases a nation’s economic, political,
and military strength.
C. Population is one of several factors that affect the environment.
1. The IPAT model represents how humans’ total impact (I) results
from the interaction among three factors—population (P),
affluence (A), and technology (T): I = P × A × T.
2. A sensitivity factor (S) can be added to the equation to denote how
sensitive a given environment is to human pressures: I = P × A × T
× S.
3. Impact can generally be boiled down to either pollution or
resource consumption.
4. Modern-day China shows how all elements of the IPAT formula
can combine to result in tremendous environmental impact in very
little time.
III. Demography
A. Demography is the science of human population.
1. The principles of population ecology apply to humans.
2. Like other organisms, humans have a carrying capacity set by
environmental limitations on our population growth.
3. Estimates of the human carrying capacity have ranged greatly—
from 1–2 billion people living prosperously in a healthy
environment to 33 billion living in extreme poverty in a degraded
world without natural areas.
B. Demography is the study of human population.
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1. The application of population ecology principles to the study of
statistical change in human populations is the focus of the social
science of demography.
2. Population size is the absolute number of individuals.
3. People are very unevenly distributed over the globe.
a. This uneven distribution means that certain areas bear far
more environmental impact than others.
b. At the same time, areas with low population density are often
vulnerable to environmental impacts. The reason they have
low populations may be that they are sensitive and cannot
support many people.
4. Age structure diagrams show the relative sizes of each age group
in a population and are especially valuable to demographers in
predicting future dynamics of a population.
5. The ratio of males to females, the sex ratio, can also affect
population dynamics.
a. The naturally occurring sex ratio in human populations at birth
features a slight preponderance of males.
b. In China, selective abortion of female fetuses has skewed the
natural sex ratio.
C. Population growth depends on the rates of birth, death, immigration,
and emigration.
1. In today’s world, immigration and emigration are playing an
increasingly large role because of the flow of refugees.
2. Since 1970, growth rates in many countries have been declining
and the global growth rate has declined, partially because of a
steep drop in birth rates.
D. A population’s total fertility rate influences population growth.
1. The total fertility rate (TFR) is the average number of children
born per female member of a population during her lifetime.
2. Replacement fertility is the TFR that keeps the size of a
population stable; for humans, it is 2.1.
3. A lower infant mortality rate has reduced people’s tendency to
conceive many children in order to ensure that at least some
survive.
4. Many other social factors play a role in reducing the emphasis on
child rearing.
5. The natural rate of population change is the change due to birth
and death rates alone, excluding migration.
E. Some nations have experienced a change called the demographic
transition.
1. Life expectancy is the average number of years that an individual
in a particular age group is likely to continue to live.
2. Demographic transition is a theoretical model of economic and
cultural change that explains the trend of declining death rates and
birth rates that occurs when nations become industrialized.
3. The first stage, the pre-industrial stage, is characterized by
conditions in which both death rates and birth rates are high.
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4. In the next stage, the transitional stage, death rates decline and
birth rates remain high.
5. The industrial stage creates employment opportunities,
particularly for women, causing the birth rate to fall.
6. In the final stage, the post-industrial stage, both birth rates and
death rates remain low and populations stabilize or decline
slightly.
7. Natural resource managers warn that despite technological
advances, the Earth does not contain enough resources for existing
and future generations to maintain a standard of living equal to
developed countries.
F. Is the demographic transition a universal process?
1. This transition has occurred in many European countries, the
United States, Canada, Japan, and several other developed nations
over the past 200–300 years.
2. It may or may not apply to all of the developing countries
depending on their culture, especially if they place greater value
on childbirth or grant women fewer freedoms.
IV. Population and Society
A. Civil Rights for women greatly affects population growth rates.
1. Drops in TFR have been most noticeable in countries where
women have gained improved access to contraceptives and
education, particularly family-planning education.
2. Unfortunately, many women still lack the information and
personal freedom of choice to allow them to make their own
decisions about when to have children and how many to have.
3. In societies in which women are freer to make reproductive
decisions, fertility rates have fallen, and the children are better
cared for, healthier, and better educated.
B. Population policies and family-planning programs are working around
the globe.
1. The government of Thailand has relied on an education-based
approach to family planning that has reduced birth rates and
slowed population growth.
2. India was the first country to implement population control
measures. After strident policies of the 1970s led to the downfall
of the government, newer policies now focus on education, family
planning services, and incentives/disincentives to better manage
the nation’s population that is expect to overtake China as the
most populated nation.
3. Brazil, Mexico, Iran, Cuba, and many other developing countries
have instituted active programs consisting of population reduction
targets, incentives, education, contraception, and reproductive
health care.
4. In 1994, the United Nations hosted a conference in Cairo on
population and development, at which 179 nations endorsed a
platform calling for all governments to offer universal access to
reproductive health care within 20 years.
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C.
D.
E.
F.
G.
5. Despite the successes of family planning internationally, the
United States has often declined to fund family-planning efforts by
the United Nations. For example, canceling this funding was one
of George W. Bush’s first acts upon becoming U.S. president in
2001.
Poverty is strongly correlated with population growth.
Consumption from affluence creates environmental impact.
1. Individuals in affluent societies leave a larger “ecological
footprint.”
The wealth gap and population growth contribute to violent conflict.
1. In 1999, the richest 20% of the world’s people used 86% of the
world’s resources, and had over 80 times the income of the poorest
20%.
HIV/AIDS is a major influence on populations in parts of the world.
1. Of the 38 million people around the world infected with
HIV/AIDS in 2004, 25 million lived in the nations of sub-Saharan
Africa.
2. The AIDS epidemic is unleashing a variety of demographic
changes.
3. Premature deaths, of both infants and young adults, are reducing
the average life expectancy in African nations.
Severe demographic changes have social, political, and economic
repercussions.
1. Everywhere in sub-Saharan Africa, AIDS is undermining the
ability of developing countries to make the transition to modern
technologies because it is removing many of the youngest and
most productive members of society.
2. Governments of AIDS-infected countries are experiencing
demographic fatigue.
V. Conclusion
A. Although global populations are still growing, the rate of growth has
decreased nearly everywhere.
B. There has been progress in expanding rights for women worldwide. In
addition to the clear ethical progress of this development, it also helps
to slow population growth.
C. True sustainability demands that we stabilize our population size in
time to avoid destroying the natural systems that support our
economies and societies.
Key Terms
demographic transition
demography
industrial stage
IPAT model
life expectancy
natural rate of population change
post-industrial stage
pre-industrial stage
replacement fertility
total fertility rate (TFR)
transitional stage
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Additional Resources
Websites
1. The Effect of China’s One-Child Family Policy after 25 Years, New England
Journal of Medicine (http://content.nejm.org/cgi/content/full/353/11/1171)
This web link is to an article in the New England Journal of Medicine
reviewing China’s attempt to control human population.
2. Country Studies: China—Population Control Programs, Federal Research
Division, Library of Congress (http://countrystudies.us/china/34.htm)
This website is part of the Country Studies/Area Handbook Series, sponsored
by the U.S. Department of the Army between 1986 and 1998, which discusses
China’s population control policy. There are also links to more current
information.
3. Population and Economic Household Topics, U.S. Census Bureau
(www.census.gov/population/www)
This web gateway provides population clocks for the United States and the
world, along with information about births, fertility, deaths, and migration in
the United States.
4. State of the World Population, United Nations Population Fund
(www.unfpa.org/swp/swpmain.htm)
This is a report by the United Nations Population Fund, the world’s largest
international source of funding for population and reproductive health
programs. Access to databases, maps, graphs, and previous years’ reports is
available.
5. UNAIDS, Joint United Nations Programme on HIV/AIDS
(www.unaids.org/en)
This web resource provides access to information, databases, and publications
concerning the global HIV/AIDS epidemic.
6. Carrying Capaity Network. (www.carryingcapacitynetwork.org)
This organization provides sobering analysis of the global human population
dynamic. Topics include revisiting the demographic transition model, foreign
aid, and the future of agriculture in meeting human nutrition needs. CCN can
also be reached at: 2000 P Street NW, Suite 31, Washington, DC 20036. 800466-4866.
Audiovisual Materials
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1. Decade of Decision, 1994, video by Population Communication International
and distributed by Bullfrog Films (www.bullfrogfilms.com)
Narrated by Walter Cronkite, this program follows the history of population
growth from the early 1900s to modern times.
2. Jam Packed, 1997, video by Population Communications International and
distributed by The Video Project (http://videoproject.com)
This program looks at the human population growth problem from a young
person’s point of view.
3. Not the Numbers Game, 1997, video produced by Emily Marlow and Jenny
Richards for Television Trust for the Environment and distributed by Bullfrog
Films (www.bullfrogfilms.com)
This six-part series looks at how women are solving population and
development problems in Bosnia, Cambodia, India, Indonesia, Peru, and
Uganda.
4. Population Six Billion, 1999, video distributed by Films for the Humanities
and Sciences (www.films.com)
This program addresses life in developing nations while providing case studies
of population control initiatives in Vietnam, Uganda, and Mexico which
include family planning, HIV/AIDS testing and counseling, and sex education.
5. Paul Ehrlich and The Population Bomb, 1996, video distributed by Films for
the Humanities and Sciences (www.films.com)
Based on Ehrlich’s book The Population Bomb, this program features archival
footage from around the world, as well as interviews with Ehrlich, his
colleagues, and his critics.
Weighing the Issues: Facts to Consider
Population Growth and Reproductive Freedom
Facts to consider: This question requires an individual response. Students
may struggle with an answer to this question because the privilege of personal
freedoms is set against Hardin’s Tragedy of the Commons. This dilemma is
especially evident in the final question of this problem, which asks students to
decide between reproductive and consumptive freedoms. Students may also
adopt a philosophy of NIMBY (Not In My Backyard) on this issue. In any
case, answers should consider resource use and exploitation of increased
populations. Students may think on a local or global level, and their answers
may reflect this focus.
China’s Reproductive Policy
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Facts to consider: Some benefits of a reproductive policy such as China’s
might include a greater ability to provide food, health care, housing, and
education, as well as reduced environmental pressure. Some problems include
social and legal punishment for people who do not follow the policy; reduction
in personal choice about family decisions; the elimination of unwanted fetuses
and children; and pressure on industry, government finances, health care,
families, and military forces because fewer working-age people are available
to support these systems. Alternative ways of dealing with the resource
demands of a quickly growing population include finding new resources to
replace depleted resources, both within the country and abroad (which may
greatly increase environmental pressure as resources become increasingly
scarce); using rewards for smaller families while refraining from punishments;
and using more efficient technologies to reduce resource-intensive processes
and to reduce pollution.
Consequences of Low Fertility?
Facts to consider: A below-replacement fertility rate means that the
population is aging. Changes in the age composition of the population will
alter patterns of consumption. Most notably, an increase in the mean
population age will trigger an increasing demand for health-care services.
Working-age people will need to supply the productivity and finances required
to support the higher proportion of older, retired people. Further observations
may also be mentioned, based on a broader student understanding of
economics and social issues.
Students may discuss increased immigration to provide a labor force; a
reduced labor force, leading to wage increases and inflation, thus decreasing
the purchasing power of retirees; greater savings rates as families spend less on
dependents; lower savings rates as older people, lacking income, spend their
savings; and increases in the retirement age so as to reduce the demands on
public welfare, as fewer younger workers are putting in funds while more older
workers receive entitlements and services.
U.S. Involvement in International Family Planning
Facts to consider: The first of these questions requires an individual response.
The second question also requires a personal response, but students can
approach the answer from a consumption/tragedy of the commons perspective
(as mentioned in the “Population Growth and Reproductive Freedom” section
on p. 73). In responding to the final question, students may use some of the
examples from the textbook, such as increased education and the availability
of contraceptives; fewer punitive measures and more positive incentives to
adhere to government policy; international monitoring groups, to ensure that
funds are used according to treaties; and measures assuring that actions taken
by those in charge of family planning do not discriminate or penalize minority
ethnic groups.
HIV/AIDS and Population
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Facts to consider: In this case, most of the people who die of complications
from AIDS are in their most economically productive years. In the short term,
increased young adult mortality skews the population structure so that there
are increased percentages of elderly people and pre-adult young people. In the
short run, governments and economies are strained by the need to provide for
orphans and the elderly. People live on more of a subsistence level, as funds
for training, education, and meeting the needs of the highly technological
world are absorbed in medical care and other areas. The result is a slow
economy with high unemployment, a shortage of trained workers, and a high
level of poverty. In the long run, the population of the country will decrease as
the natality rate decreases due to the increased mortality of child-bearing
females. The population structure will shift again as there are fewer children
available to enter the workforce, further hampering the economy. Population
stabilization will eventually take place, but it may take generations before it is
reached.
The Science behind the Stories: Thinking Like a
Scientist
Causes of Fertility Decline in Bangladesh
Observation: In Bangladesh—one of the most densely populated countries on
the planet—fertility declined dramatically from the late 1970s through the
1990s despite high rates of poverty, illiteracy, and gender inequality.
Hypothesis: The Bangladeshi government and international aid organizations
began an aggressive campaign in the mid-1970s to provide women with access
to and information about contraceptives.
Experiment: Researchers measured the impact of outreach efforts on
contraceptive use and fertility rates in Matlab, an isolated rural area in
Bangladesh with a high-intensity family-planning outreach project. Matlab was
compared to a similar government-run program, which had a lower amount of
training, services, and community visits.
Results: In 1988, ten years after the study began, Matlab Project director
James Phillips and his colleagues reviewed a decade’s worth of data collected
by the highly organized health surveillance system already in place. It was
found that contraceptive use in Matlab was higher and fertility was lower than
in the comparison area. The results suggested that Bangladesh’s success was
due to a combination of widely available contraceptives and socially
appropriate family planning services, both of which were present in an
intensified form in Matlab.
Question: Why was Matlab so successful in reducing fertility rates?
Hypothesis: Frequent visits from health-care workers helped to convince
women that small families were desirable.
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Study: Mary Arends-Kuenning of the University of Michigan surveyed
families and visiting health workers about the health-care workers’ visits.
Results: Arends-Kuenning and her colleagues found no correlation between
the patients’ perception of family size and the number of visits made by healthcare workers, in either the Matlab study area or the control area with the
government-run program. It was proposed that the reason for the Matlab
Project’s success was that it helped women to realize an already-existing
desire to have fewer children by providing readily available contraceptives and
education.
AIDS Resistance Genes and the Black Death: An
Unexpected Connection?
Observation: Some individuals are resistant to HIV.
Hypothesis: The immune system of these individuals somehow prevents HIV
from infecting its cells.
Study: Stephen O’Brien, Michael Dean, and other researchers of the National
Cancer Institute studied HIV-resistant individuals for physiological anomalies
pointing to genetic mutations that would allow these individuals to be HIV
resistant.
Results: The research team found that HIV infects cells through the cellular
receptors for an immune cell communication system—the chemokines. Further
studies found that HIV-resistant people had mutations to the chemokine
receptor CCR5 on macrophages. If the person had two copies of the mutation,
they were resistant to HIV. One copy of the mutation slowed the development
of AIDS, and persons without mutations were completely vulnerable to HIV
and AIDS.
Observation: CCR5 mutations were not evenly spread out among the human
population, being found in only 9% of Caucasians and missing entirely from
Japanese, Africans, and other ethnic groups.
Question: Why was the CCR5 mutation limited only to Europeans and their
descendants?
Study: Dean and O’Brien’s team analyzed linkages between the alleles of the
genetic mutation. By examining how weak the linkages were to the allele for
the CCR5 mutation, the team was able to determine approximately when the
mutation first occurred.
Results: Researchers found the mutation to be approximately 700 years old,
which placed the mutation’s origin at about the same time that the Black Death
ravaged Europe. This occurrence seemed to make sense, as the bacterial
pathogen for bubonic plague attacks macrophages in much the same way as
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does HIV. Survivors of the plague would retain the genetic mutation that
allowed them to survive, causing the allele frequency of the mutation to
increase.
However, as is always the case in science, doubt was cast on these results by
other researchers. The research group of Joan Mecsas at Stanford University
found that mice with the CCR5 mutation were not protected from bubonic
plague. In addition, two researchers at the University of California at Berkeley
used a modeling study of disease population dynamics to show that the plague
was not the most likely selection pressure for the CCR5 mutation. These
researchers hypothesize that smallpox was the selection pressure, since it also
caused many deaths in the Middle Ages.
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