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Chapter 4. The Human Population and the Environment. Basic Concepts of Population Dynamics. Population: 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.

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chapter 4

Chapter 4

The Human Population and

the Environment

Botkin & Keller

Environmental Science 5/e

basic concepts of population dynamics
Basic Concepts of Population Dynamics
  • Population:
    • 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.

Botkin & Keller

Environmental Science 5/e

age structure
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.

Botkin & Keller

Environmental Science 5/e

forecasting population change
Forecasting Population Change
  • Formula to represent population change:

P2 = P1 + (B – D) + (I – E)

Botkin & Keller

Environmental Science 5/e

slide5

Fig 4.3

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

a brief history of human population growth
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.

Botkin & Keller

Environmental Science 5/e

slide7

Fig 4.4a

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

slide8

Fig 4.4b

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

slide9

Fig 4.4c

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

slide10

Fig 4.5

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

slide11

Fig 4.6

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

projecting future population growth
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

Botkin & Keller

Environmental Science 5/e

slide13

Fig 4.7

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

slide14

Fig 4.8

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

the demographic transition
The Demographic Transition
  • 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.

Botkin & Keller

Environmental Science 5/e

slide16

Fig 4.9

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

population and technology
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

Botkin & Keller

Environmental Science 5/e

the human population the quality of life and the human carrying capacity
The Human Population, the Quality of Life, and the Human Carrying Capacity
  • 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

Botkin & Keller

Environmental Science 5/e

human death rates and the rise of industrial societies
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

Botkin & Keller

Environmental Science 5/e

slide20

Fig 4.10

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

will aids stop population growth
Will AIDS stop population growth?

Worldwide 33.6 million have AIDS or HIV

Compare this to 84 million people added to world/year

Botkin & Keller

Environmental Science 5/e

longevity and its effect on population growth
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

Botkin & Keller

Environmental Science 5/e

limiting factors
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

Botkin & Keller

Environmental Science 5/e

tfr and replacement fertility rate
TFR and Replacement Fertility Rate

TFR: Average number of children born during a woman’s lifetime

  • 3.8 in U.S. during post was “baby boom”
  • Approx. 2.0 now (replacement rate/2.1)
  • Bangladesh 3.3
  • Brazil 2.3
  • p. 184 (R&B)

Botkin & Keller

Environmental Science 5/e

slide25

Fig 4.11

Botkin & Keller

Environmental Science 5/e

© 2005 John Wiley and Sons Publishers

how can we achieve zero population growth
How Can We Achieve Zero Population Growth?
  • Delay the age of first childbearing by women (marriage age increase)
  • Educate Women (single most important factor)
  • Encourage Women to breast-feed
  • Encourage family planning
  • Encourage national programs to reduce birth rates
    • China (1.2% in 1978 to 1.0% in 2000)

Botkin & Keller

Environmental Science 5/e