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Lecture Outlines

ENVIRONMENT the science behind the stories

Chapter 8

Human Population

Lecture objectives  Describe the scope of human population growth.  Discuss divergent views on population growth.  Explain how human population, affluence, and

technology affect the environment.  Explain the fundamentals of demography.  Describe the concept of demographic transition.  Explain how family planning, the status of women,

and affluence affect population growth.

Case Study: Will China’s New “Two-Child Policy” Defuse Their Population “Time Bomb”?  In 1970, China instituted a population control

program that restricted most couples to a single child.

 Efforts included increased accessibility to contraceptives and abortion, rewards for single-child families, and fines and social scorn for those with more.  Fertility rates dropped from 5.8 to 1.7 children per

woman.  The growth rate dropped from 2.8% to 0.5%.

 The one-child policy created problems—the population’s labor force shrank, the percentage of elderly increased, and there were too few women.  The decrease in young

workers has made it difficult for employers, and may affect the economy.  The culturally increased

value of male children combined with the one-child policy had lead to selective abortion and the killing of female children.  The male-to-female ratio is unbalanced, creating large

numbers of young men who cannot marry.

 The population “time bomb” of an aging population and skewed male-to-female ratios has lead to a change in Chinese policies.  In 2013, married couples that were only children were

granted permission to have two children.  In 2015, the one-child policy was immediately altered

to a two-child policy.  It is unclear how many Chinese couples, used to

greater wealth and an urban lifestyle, will grow their families.

Our World at Seven Billion  China is not the only country with population issues;

India lacks similar stringent policies and will soon become the most populous country.  The current population is over 7.3 billion, with most of

the growth is in poorer nations.

The human population is growing rapidly  The human population is currently growing at a rate

of 88 million per year; that is 2.8 people added every second.  The human population didn’t reach 1 billion until after

1800.  A billion people are currently being added about every

12 years.

 This is an example of exponential growth, where a small percentage growth rate still produces a large increase due to the size of the base population.

 Population growth rates vary from place to place.  The doubling time of a population can be estimated

by taking the number 70 and dividing it by the annual percentage growth rate.  Global doubling time is 70/1.2%, or 58 years.  China’s doubling time prior to the one-child policy was

70/2.8%, or about 25 years.

Is population growth a problem?  Improved sanitation, modern medicine, and higher

agricultural output have all helped to reduce the infant mortality rate, the frequency of children dying in infancy.  This is a very good thing—so why is population

growth a problem?

 Prior to the industrial revolution, high birth rates were considered positive.  More children to support

parents in old age, and a greater pool of labor for factory work.

 British economist Thomas Malthus argued that the number of people would eventually outgrow the available food supply.  Paul and Anne Ehrlich of Stanford University have

been called “neo-Malthusians” because they have made similar warnings.

 Despite a quadrupling of the human population, these predictions have not fully materialized.  Food production has intensified.  Enhanced prosperity, education, and increasing

gender equity have helped to slow birth rates.  In spite of these improvements, population growth

still depletes resources, stresses social systems, and degrades the natural environment.

Population is one of several factors that affect the environment  The IPAT model represents how our total impact (I)

on the environment results from the interaction of population (P), affluence (A), and technology (T). I = P × A × T  Increased population means more individuals take up

space, use resources, and generate waste.  Affluence leads to greater per capita resource

consumption.  Technology can increase impact by enhancing our

ability to exploit resources or decrease impact by improving efficiency.

 A sensitivity factor (S) may also be added to denote the vulnerability of a given environment. I = P × A × T × S  For example, the arid lands of western China are

more sensitive to human disturbance due to the slow growth rate of the plants there.

 Modern-day China has many examples of how IPAT elements can create environmental impact.  Intensive agriculture has caused erosion in western

China similar to the Dust Bowl.  Aquifers and rivers are heavily withdrawn.  Air quality is so low in Beijing, that breathing it for a

Review Questions 1. As shown by this graph, the human population is

experiencing _____ growth. a. linear b. exponential c. logistic d. negative

Review Questions 2. According to the IPATS model, which of these

changes would reduce environmental impact? a. An increase in the overall affluence of the global

society b. An decrease in the human population growth rate c. Technological advances in resource harvesting d. Consuming resources in a more sensitive

environment

Demography  Principles of population ecology can be applied to

the study of statistical changes in the human population.  This is called demography.

 Despite our ability to use technology to keep up with our population growth, our knowledge of population ecology and logistic growth suggests that this cannot continue indefinitely.

Demography is the study of the human population  Demographers study several characteristics of the

human population:  Size  Distribution  Age structure  Sex ratio  Rates of birth, death, emigration, and immigration

 The current population size is about 7.3 billion, spread amongst 200 nations.  The United Nations

predicts that by 2050, the global population will surpass 9.7 billion.

 Many other demographic aspects determine environmental impact besides size.

 In ecological terms, the global distribution of people is clumped.  Highest human densities are found in temperate,

subtropical, and tropical climates.

 Age structure diagrams, also called population pyramids, describe the relative numbers of individuals at each age class within a population.  This is valuable in predicting the future growth of a

population.

 A pyramid with a wide base denotes a large proportion of pre-reproductive age people, and the potential for rapid future growth.

 A pyramid with an even age distribution will indicates a stable population.

 A pyramid with a higher proportion of post- reproductive age adults indicates a shrinking population.

 For example, Nigeria’s large concentration of individuals in young age groups predicts a much greater population growth rate than Canada.

 The global population is older than past years.  The median age today is 28; in 2050 it is predicted to

be 35.  This creates strain in social welfare programs in

some countries, as fewer young workers are supporting more elderly.

 The naturally occurring sex ratio at birth for human populations is 106 males born per every 100 females born.  This is likely an evolutionary adaptation to the

increased mortality rate faced by males at all ages.  In China, age distributions have become

increasingly skewed.

 The cultural gender preference for male children, coupled with the one-child policy, has resulted in roughly 116 Chinese boys are born for every 100 girls.  The leading hypothesis is that many parents are

using ultrasounds to determine the gender of their unborn fetus, then selectively aborting females.

Population change results from birth, death, immigration, and emigration  Births and immigration add individuals to a

population.  Death and emigration remove individuals from a

population.  Global decreases in infant mortality rates have

played a large role in population growth.  Historically, families would have many children as

“insurance” against the likelihood of one or more of them dying in infancy due to poor nutrition, disease, and exposure.

 Infant mortality rates are closely tied to a nation’s level of industrialization.  China, for example, saw its infant mortality rate drop

from 47 children per 1000 live births in 1980 to 16 children per 1000 live births in 2013.

 In recent decades, falling growth rates in many countries has lead to an overall decline in the global growth rate.  This is primarily due to a

steep drop in birth rates.  Immigration and

emigration also significantly impact the population of individual nations.

Total fertility rate influences population growth  Total fertility rate (TFR) is the average number of

children born per woman during her lifetime.  Replacement fertility is the TFR that keeps the size

of a population stable. For humans, this is 2.1.  Industrialization, improved women’s rights, and

health care have decreased TFR in many nations in recent years.  Nearly every European nation has a TFR below

replacement level.

 Worldwide, by 2015, 84 countries have fallen below the replacement fertility level.

 Europe’s rate of natural increase, which only includes birth and death rates, was between 0.0% and 0.1% in 2015.

Many nations are experiencing the demographic transition  Industrialized countries tend to have the highest life

expectancy, the average number of years a person in an age group is expected to live, increases due to a drop in infant mortality.

 Countries still industrializing will pass through a series of stages of economic and cultural change called the demographic transition.

 During the pre-industrial stage, death rates are high due to widespread disease, rudimentary health care, and unreliable food supplies.

 People compensate for high infant mortality by having many children. Birth control is not available.  Population growth, overall, is stable.

 Death rates decline during the transitional period, due to improved food production and health care.

 Birth rates remain high as society has not yet adjusted to the new economic conditions.  Overall population growth rate is very high, too.

 During the industrial stage, employment opportunities increase for women and birth control becomes more widely available, decreasing birth rates.  Population growth slows and begins to stabilize.

 The population growth stabilizes or begins to shrink during the post-industrial stage.  The United States is in this stage, although it has

higher birth rates due to an increased immigration rate.

Is the demographic transition a universal process  The demographic transition has occurred in many

European countries, Canada, the United States, Japan, and others.

 Some developing countries are so overpopulated that they may not be able to complete a transition, creating demographic fatigue.  Many sub-Saharan African countries, given their high

populations and prevalence of HIV/AIDS, are in this position.

Review Questions 3. A country with a population pyramid shaped like

this most likely has a _____ population. a. stable b. growing c. shrinking d. fluctuating

Review Questions 4. Japan’s total fertility rate is 1.4. By comparing this

to the replacement fertility level, their population is assumed to be a. growing rapidly. b. growing slowly. c. stable. d. shrinking.

Review Questions 5. A country is experiencing a decrease in death rates

due to improvements in the food supply and health care. Its birth rates, however, remain high and their population is growing rapidly. In what stage of the demographic transition model is this country? a. Preindustrial b. Transitional c. Industrial d. Post-Industrial

Population and Society  There are many economic and societal factors that

affect fertility in a nation.  Access to contraceptives  Acceptance of contraceptive use  Level of women’s rights  Cultural influences, such as television programs  Level of affluence  Importance of child labor  Availability of governmental support for retirees

Family planning is a key approach for controlling population growth  Family planning is the effort to plan the number

and spacing of one’s children.  Birth control includes all efforts to reduce the

frequency of pregnancy.  Contraception is a deliberate attempt to prevent

pregnancy despite engaging in sexual intercourse.  Many family-planning organizations provide free or

discounted condoms, spermicides, hormonal treatments, or surgical sterilization.  Rates of use range from 84% in China and the U.K. to

 Low contraceptive use may be a combination of low availability (especially in rural areas) and a lack of acceptance due to religious or cultural doctrines.

 Access to family planning gives women control over their reproductive window, the time at which they can become pregnant.

Family-planning programs are working around the world  Rapidly growing countries have implemented family-

planning programs, most less intrusive than China’s one-child policy.  Thailand, for example, achieved a reduction in growth

rate from 2.3% in the 1960s to 0.4% in 2015 through increased education of family-planning techniques and improved access to contraceptives.

Empowering women reduces fertility rates  In order to reduce fertility

rates, women must be given equality in decision-making power and access to education and job opportunities.

 Equal rights also leads to women having the ability to make reproductive decisions themselves, leading to further drops in fertility rates and overall better care for children.

Increasing affluence lowers fertility  Poorer societies tend to

show higher population rates than wealthier ones.

 Economic factors are tied closely to population growth.  Poverty exacerbates

population growth.  Rapid population growth

worsens poverty.

 Most of the next billion added to the human population will come from emerging economies, meaning that:  Those countries

will continue to be economically strained.  Environmental

degradation will continue due to poverty.

Expanding wealth can increase the environmental impact per person  Wealth can produce even more severe

environmental impacts than poverty.  Affluence is built on unsustainable levels of resource

consumption.  The addition of 1 person from a wealthy country like

the United States has the same impact as 3.4 Chinese, 8 Indians, or 14 Afghans.

 One analysis concluded that humanity is now living 50% beyond our means, which in ecology would be termed an overshoot.

 The amount of biologically productive land available to us is called biocapacity.  If humanity’s ecological footprint exceeds this, it is

termed an ecological deficit.  If the footprint is less, there is an ecological reserve.

Population goals support sustainable development  The factors that influence fertility are complex and

interacting, so initiatives to slow growth must be diverse, flexible, and culturally specific.

 A 1994 U.N. conference proposed a movement away from a top-down command-and-control policy geared toward providing birth control to a bottom-up policy that addresses poverty and social needs first.  There is no “one-size-fits-all” solution; each must be

tailored to the nation it is serving.

Review Questions 6. Which of these factors has a positive correlation

with fertility rates and population growth? a. Higher levels of affluence b. Higher rates of education for women c. Economic poverty d. Women having equal say in family planning

Review Questions 7. Which of these is a TRUE statement regarding the

current world population and global ecological footprint? a. Poorer nations, due to their high growth rates, have

a greater ecological footprint. b. The human population has an ecological footprint

less than the global biocapacity. c. The human population is generating an ecological

reserve. d. The human population is generating an ecological

debt.

Slide Number 1
Lecture objectives
Case Study: Will China’s New “Two-Child Policy” Defuse Their Population “Time Bomb”?
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Slide Number 5
Our World at Seven Billion
The human population is growing rapidly
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Is population growth a problem?
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Slide Number 12
Population is one of several factors that affect the environment
Slide Number 14
Review Questions
Review Questions
Demography
Demography is the study of the human population
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Slide Number 20
Slide Number 21
Slide Number 22
Slide Number 23
Slide Number 24
Slide Number 25
Slide Number 26
Population change results from birth, death, immigration, and emigration
Slide Number 28
Slide Number 29
Total fertility rate influences population growth
Slide Number 31
Many nations are experiencing the demographic transition
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Is the demographic transition a universal process
Review Questions
Review Questions
Review Questions
Population and Society
Family planning is a key approach for controlling population growth
Slide Number 43
Family-planning programs are working around the world
Empowering women reduces fertility rates
Increasing affluence lowers fertility
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Expanding wealth can increase the environmental impact per person
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Population goals support sustainable development
Review Questions
Review Questions