Chapter 7: Human Populations
Population Growth
World population reached 6 billion in July, 1999
There are various views as to the impact of rapid population growth
• Growth beyond carrying capacity may threaten the ecological
balance of the world
• More people may be beneficial, i.e., more hands and brains to
solve problems (supported by economists)
• Growth is only a symptom of mis-managed resources that have
the potential to support everyone
Human Population History
World population grew slowly until relatively recently
Many factors contributed to a slow, steady population growth
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Cultural practices such as infanticide
Epidemic disease and famine
War
Period of rapid growth that we are experiencing now raises questions
• Can high levels of growth be maintained?
• Will a dieback of our population serve to balance the current
trend?
Limits to Growth: Some Opposing Views
Malthusian Checks on Population
Rev. Thomas Malthus, 1798
• Theory predicted collapse of human population due to lack of food
supply
• He believed population growth supported increases in starvation,
poverty, social ills
• Supported idea that (1)destructive and (2) preventative checks could
slow population growth
(1) Disease or famine
(2) Moral restraint or celibacy to curb reproduction
Karl Marx - A critic of Malthus
• Population growth is a symptom of social injustice rather than a cause
• Supported the idea that productive, working citizens could always
provide for themselves and society
Malthus and Marx Today
Neo-Malthusians: Name for supporters of Malthus and support
predictions of exceeding the world carrying capacity
Neo-Marxians: Name for supporters of Marx and support use of
technological improvements to equalize social injustices and
solve population problems
Can Technology Make the World More Habitable?
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Food production is outpacing population growth
• Easy acquisition of resources has supported increased carrying
capacity
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Technological advancements:
- Medicine
- Sanitation
- Commerce
- Agricultural productivity
Can More People Be Beneficial?
More people may mean more intelligence for problem solving and
creating new resources
Julian Simon: A primary supporter of humans existing as the ultimate
resource
Human Demography
Demography: to write or measure e.g., birth, death, and growth rates of
people
How Many of Us Are There?
Exact numbers are unavailable due to political instabilities and
inaccurate record keeping
Most growth is expected in less developed countries
• To check the current and predicted world population size, go
look at the World
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Population Clock (close the new window to return to these
pages). (located at "http://sunsite.unc.edu/lunarbin/worldpop")
Fertility and Birthrates
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Fertility rate describes actual production of offspring
Crude birthrate: unadjusted for number of births per thousand
individuals
Total fertility rate: average number of children per life time
Zero population growth (ZPG): number of births needed for a
stable population
Examples:
- Fertility Rate for developed countries = 2.1
- Fertility Rate for the world = 2.8
High fertility usually associated with poverty: e.g., Sub-Saharan
Africa
Low fertility associated with low level of modernization, and high
death rates: e.g., Eastern Block countries
Fertility and Birthrates
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Fertility rate describes actual production of offspring
Crude birthrate: unadjusted for number of births per thousand
individuals
Total fertility rate: average number of children per life time
Zero population growth (ZPG): number of births needed for a
stable population
Examples:
- Fertility Rate for developed countries = 2.1
- Fertility Rate for the world = 2.8
High fertility usually associated with poverty: e.g., Sub-Saharan
Africa
Low fertility associated with low level of modernization, and high
death rates: e.g., Eastern Block countries
Mortality and Death Rates
High rate: 20/1000 in African countries
Low rate: 5/1000 in young, growing countries: e.g., Belize
Population Growth Rates
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Annual Death rate subtracted from Birthrate = natural increase (%)
- Divide percent (# per 100) into 70 = approximation of years to
double population
Total growth rate includes natural increase plus immigration and
emmigration
Examples:
- Even though the United States and Canada have the same rate of
natural increase (0.8% per year), the total growth rate, which
includes immigration and emmigration, is much faster for the
U. S. (high immigration, low emmigration compared to Canada)
- Fast: Afghanistan = 5.3% per year
- Slow: Eastern Europe = negative, with declining populations
- World growth rate = 1.4% per year, doubles every 50 years
Life Span and Life Expectancy
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Life span is the oldest absolute age of an individual
Life expectancy is the average age at death for a population
- Life expectancy has increased due to better food and sanitation
reducing mortality
- If life expectancy changes, many facets of society will also
change: expected to be over 60 years of age for U.S.
in 2100
Living Longer: Demographic Implications
• As developing countries gain access to education, medicine, and
sanitation, life expectancy increases
• Over past 100 years: life expectancy increased from 40 to 65.5 years
of age worldwide
• Good correlation between income and life expectancy (up to about
$4,000 U.S.)
- levels out at 75 years of age for men, 80 for women
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Age structure has impact on society
- A large ratio of young citizens will affect population fertility for
long periods, population momentum, e.g., Mexico
- A large ratio of old citizens will affect productivity, dependency
ratio
Emigration and Immigration
• 38 million people left home countries in 1997
• Refugees can affect places they leave and the places they move into
e.g., uninhabited rainforest seen as a good place to move from crowded
cities
• Movement of large numbers of people can create ecological,
financial, and social change
Population Growth: Opposing Factors
Pronatalist Pressures
• A strong desire to have children is more important than inadequate
contraception
• Number of children often linked to societal status
Birth Reduction Pressures
• Developed countries: education and socioeconomic status are inversely
related to fertility. Families tend to commit to a low
number of highly cared for children
• Undeveloped countries: as education and socioeconomic status rise so
does fertility
Birth Dearth?
A lack of replacement births can affect many aspects of a
productive country
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Military strength
Work force
Taxpaying workers
Demographic Transition
Transition from high birth and death rates to lower birth and death
rates
Development and Population
As death rates fall and birthrates remain high in some developing
countries, total population growth transition curves are unexplained by
past experience
An Optimistic View
Fertility rates are dropping in developing countries such as Morocco,
Peru, Columbia, Thailand, Jamaica, and Mexico
Developing countries are experiencing the technological benefits that
move from developed countries which reduce needs for large families
A Pessimistic View
Lester Brown, Garret Hardin
Lifeboat analogy: wealthy countries are in well supplied, uncrowded
lifeboats. If these lifeboats admit struggling survivors, soon the boat is
overcrowded and no better than the crowded boat left by the survivor.
Resources cannot be shared by all.
A Social Justice View
There may be enough resources for everyone if they are distributed in a
fair and equal system of social justice
May be important to share resources from wealthy nations with
developing nations due to inherent sharing of the environment
An Ecojustice View
Seeking the optimum number of people that provides a fair and decent
life for all humans while causing the minimum impact on
nonhuman species. Considers the 'right' of all species to exist.
Infant Mortality and Women’s Rights
Reductions in infant mortality always precede reductions in birthrates
Child survival will benefit from and increase in adult female rights and
opportunities
Family Planning and Fertility Control
Birth control: any method to control births
Traditional Fertility Control
Ancient societies maintained stable population sizes
Use of social conventions, medicines, abortions, infanticide
Current Birth Control Methods
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Avoidance of fertile periods: rhythm method
Mechanical barriers: Female condom
Surgical methods to prevent release of gametes
Chemicals: Norplant: sub-cutaneous implanted, slow release
progesterone; RU486, the morning after pill
Physical disruption of implantation, IUD
abortion
New Developments in Birth Control
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Vaginal rings loaded with progesterone
Anti-pregnancy vaccines
Anti-sperm vaccines
Sperm and egg suppression chemicals: gonadotropin releasing
hormone agonists
The Future of Human Populations
• An expected equilibrium world population is 8 -10 billion
• Change is required for a stable and sustainable world population
• Approximately 50% of married couples in the world use family
planning
- Family planning success needs:
- Improved women's rights
- Improved status for children
- Support for fertility decision making
- Social and political stability