1. The Human Population and the Environment
Chapter 4
The Human Population and
the Environment

2. Basic Concepts of Population Dynamics
A group of individuals of the same species living in the same area of interbreeding and sharing genetic information.
Species:
All individuals that are capable of interbreeding.
Made up of populations
Population dynamics
The general study of population changes.

3. Age Structure Population age structure:
The proportion of the population in each age class
Affects current and future birth rates, death rates and growth rates
Has an impact on the environment
Has complications for current and future social and economic status.

4. Forecasting Population Change
Formula to represent population change:
P2 = P1 + (B – D) + (I – E)
P1=Number of individuals in pop. at time 1
P2=Number of individuals in pop. at time 2
B=Births from time 1 to time 2
D=Deaths from time 1 to time 2
I=Number of immigrants from time 1 to time 2
E=Number leaving as emigrants

5. © 2008 John Wiley and Sons Publishers

6. A Brief History of Human Population Growth
Hunters and gatherers
The world’s population was probably less than a few million
Early, pre-industrial agriculture
Allowed a much greater density of people
The first major increase in human population
Machine age
Industrial revolution led to rapid increase in human population
The Modern era
Rate of population has slowed in wealthy nations but continues to increase rapidly in poorer, less developed nations.

7. © 2008 John Wiley and Sons Publishers

8. Human population from 1000 A.D. to 2000 A.D.
© 2008 John Wiley and Sons Publishers

9. Past and forecasted human population growth rate by geographic region and major nations
© 2008 John Wiley and Sons Publishers

10. Logistic growth curve. World population as total numbers and growth per decade and by development status
© 2008 John Wiley and Sons Publishers

11. United States population 1790-2000
United States population Growth rate of the US population appears to be slowing.
© 2008 John Wiley and Sons Publishers

12. Projecting Future Population Growth
Exponential growth and doubling time
The logistic growth curve
“S” shaped curve that is generated by the logistic growth equation.
A small population grows rapidly
But the growth rate slows down
The population eventually reaches a constant size.
Logistic carrying capacity
The population size at which births equal deaths and there is no net change in population

13. © 2008 John Wiley and Sons Publishers

14. © 2008 John Wiley and Sons Publishers

15. The Demographic Transition
Three-stage pattern of change in birth rates and death rates.
Occurred during the process of industrial and economic development of Western nations.
Leads to a decline in population growth.
Stage I: Decline in death rate
Stage II: High growth rate
Stage III: Birth rate drops toward the death rate, leading to low or zero growth rate.

16. © 2008 John Wiley and Sons Publishers

17. © 2008 John Wiley and Sons Publishers

18. Population and Technology
The total impact of the human population on the environment is:
the average impact of an individual multiplied by the total number of individuals
T = P x I
P=population size
I=average environmental impact per person

19. The Human Population, the Quality of Life, and the Human Carrying Capacity
The number of people that can live on Earth at the same time?
To determine:
Extrapolate from past growth
The “Packing Problem” approach
Considers how many people might be packed onto Earth, not taking into sufficient account the need for lands and oceans to provide food, water, energy, construction materials, and scenic beauty and the need to maintain biological diversity

20. Human Death Rates and the Rise of Industrial Societies
Acute or epidemic disease
Appears rapidly in the population,
Affects a comparatively large percentage of it,
Declines then almost disappears, only to reappear later
Chronic disease
Is always present in a population
Typically occurs in a relatively small but relatively constant presentation of the population
Examples include heart disease, cancer, and stroke

21. © 2008 John Wiley and Sons Publishers

22. Longevity and its Effect on Population Growth
Maximum lifetime:
The genetically determined maximum possible age to which an individual of a species can live
Life expectancy:
The average number of years an individual can expect to live given the individual’s present age

23. Some factors fit into more than one category
Limiting Factors
Short-term factors
Those that affect a population during the year in which they become limiting
Intermediate-term factors
Those whose effects are apparent after one year but before ten years
Long-term factors
Those whose effects are not apparent for ten years
Some factors fit into more than one category

24. Life expectancy in ancient Rome and 20th century England
Approximate survivorship curve for Rome for the first four centuries A.D.
© 2008 John Wiley and Sons Publishers

25. How Can We Achieve Zero Population Growth?
Delay the age of first childbearing by women
Birth control
Biological and Social
Breast-feeding, which can delay resumption of ovulation
Abstinence
Induction of sterility with natural agents
Contraceptive devices
National Programs to Reduce Birth Rates
Formal family planning programs to
explain the problems arising from rapid population growth
Describe the benefits to individuals of reduced population growth.