CHAPTER 6
THE HUMAN POPULATION

I. The Population Explosion

A. Current world population: 6 billion people (October 1999)

B. Putting the numbers in perspective:
1. Each time your heart beats, 3 more people are added to the world
2. Each time a person dies, 2.8 babies are born

C. Causes of population growth:
a. Better recruitment resulted from declining infant mortality rates
b. Mortality rates decline:
·Improvement in agriculture  increased production and better food
distribution and storage
·Public health measures  improved sanitation practices, clean drinking
water, mass inoculations
Fig. 6.1 For most of human history, population grew slowly, but in modern times it has suddenly "exploded."
Fig. 6.2  Declining fertility rates in the last three decades have resulted in a decreasing rate of growth. However, absolute numbers are still adding 80 million per year.
II. Different Worlds

A. Rich Nations

1. Decreased birth rates
2. Low to negative growth rates
3. Increased consumption rates per person
4. Negative environmental impact due not to numbers but affluence.
5. Consequences of affluence
a. Greater contribution per person to global pollutants  carbon dioxide,
ozone depletion chemicals
b. Food consumption high on biomass pyramid  fewer people can be
supported
c. Waste production high  fuel inefficient transportation, throwaway
consumer goods.

B. Poor Nations

1. Moderate birth rates (these rates have decreased in the last 20 years)
2. Moderate to high growth rates
3. Low consumption rates per person
4. Negative environmental impact due to numbers not affluence
5. Consequences of population size
a. Subdividing farms and intensifying cultivation
b. Opening up new lands for agriculture
c. Migration to cities
d. Illicit activities
e. Emigration and immigration
f. Impoverishment of women and children
Fig. 6.3 This figure shows nations of the world  according to gross national product per capita. The population in millions of various regions is also shown by magenta lines and numbers.
Fig. 6.4 Developing countries represent a larger and larger share of world population because of higher populations and higher birth rates.
Fig. 6.7 This figure shows the growth of some major world metropolitan areas. Since 1965, cities in the developing world have grown phenomenally, and a number of them are now among the world's largest.
Fig. 6.9 The diagram shows the numerous connections between unchecked population growth and social and environmental problems.
III. Dynamics of Population Growth

A. Population Profiles
1. Age Structure of Population  relative numbers of young, middle age and old

B. Population Projections
1. Total fertility rate
2. Replacement level fertility
3. Birth rates and death rates (infant and childhood mortality)
4. Doubling time

C. Variation of Population Projections by Country
1. Population projections for a more developed country
2. Population projections for a less developed country
Fig. 6.10 The age structure of the U.S. population, showing the effects of major shifts in fertility.
Fig. 6.11 This figure shows projected world population according to three different fertility scenarios. UN projections of the future world population, using different total fertility rates.
Fig. 6.12 This figure shows a population profile representative of a highly developed country, Denmark.
Fig. 6.13 Projections shift drastically with changes in fertility. Contrast the 1988 projection, based on a fertility rate of 1.8, with the 1993 projection, based on the increased fertility rate of 2.13.
Fig. 6.14 Even if the total fertility rate in Kenya immediately dropped to 2, the number of births (hatched inner portion of the bottom two bars) would still greatly exceed the number of deaths because so few persons are in the upper age groups.
Fig. 6.15 This figure shows population profiles for developed
and developing countries, projected to the year 2025.
D. The Demographic Transition

1. Epidemiologic transition
a. Pattern of change in mortality factors
b. Decline in death rates

2. Fertility transition
a. Pattern of change in crude birth rates
b. Decline in birth rates worldwide

3. Phases of demographic transition
a. The demographic transition is a description of the correlation observed in
developed countries between economic development and decreased fertility
rates. There may be other, equally effective means of reducing fertility rates.
Fig. 6.16 The epidemiologic transition and the fertility transition combined to produce the demographic transition in the developed countries over many decades.
Fig. 6.17 Crude birth rates and crude death rates are shown for major regions of the world.
A dividing line separates countries at or well along in the demographic transition from those apparently stuck in the middle of the transition.