CHAPTER 4 continued The Demographic Transition

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CHAPTER 4 (continued)The Demographic Transition

• Understanding how a population makes the
  transition from one which is growing
  exponentially with high fertility rates to one
  which is
• stabilizing, and
• birth rates are beginning to equal death rates

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THE FOUR STAGE MODEL

• Pre-industrial harsh conditions gave rise to a
  high birth rate to compensate for a high infant
  mortality rate. There was also a high death rate
  often at an earlier age.
• The early industrial age A decline in death rate
  due to improvements in living conditions, food
  and water supplies.
• Some countries seem to still be at this stage and
  in a demographic trap. Still high birth rates
  coupled with lower death rates.

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THE MODEL continued

• The industrial stage Declining birth rate that
  begins to approach the death rate slows
  population growth. Factors include birth control
  access, better opportunities for women, better
  health care.
• The post industrial stage Birth rate equals or
  falls below death rate. Zero population growth is
  achieved.

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ZERO POPULATION GROWTH

• In theory, the logistic growth curve can predict
  the eventual population size or carrying capacity
  in specific nations and the planet.
• However, there are many factors that influence
  population size education, health, environmental
  conditions, technology, among others.

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DISEASES

• Historically, diseases and specifically pandemics
  have had a major impact on population.
• The Plague, or Black Death, in the Middle Ages
  killed millions of people.
• Cholera and malaria continue to affect children.
• Influenza ( the flu) is always a threat to the
  elderly.
• AIDS and SARS are more recent additions to the
  arsenal of diseases.

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DISEASES

• As indicated in the text, there is a concern that
  the use and overuse of antibiotics,
  anti-bacterial cleaning compounds is causing more
  mutations in bacteria and other disease-causing
  organisms, resulting in more resistant strains.
  This has happened with insects in the case of
  insecticides.
• How clean do our homes need to be?

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CARRYING CAPACITY

• The maximum number of organisms, eg humans, that
  a particular habitat can support sustainably in
  the long term.
• In the case of humans, this must consider
  primarily the land areas that are productive and
  can support life.
• In addition, this calculation has to consider
  that if we exceed the carrying capacity, we will
  change the environment on which we depend.

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MALTHUS

• Theorized that the geometric growth in the human
  population would exceed the food supply
  Assuming, then, my postulata as granted, I say
  that the power of population is indefinitely
  greater than the power of the earth to produce
  subsistence for man. Malthus,1798. Essay on the
  Principle of Population.

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ERLICH

• In the Population Bomb (1968) predicted famine
  and disaster for hundreds of millions of people
  in the late 1970s and 1980s.
• He called for population control programs in the
  U.S.and elsewhere.
• He was basing his predictions on models that
  assumed growth would continue at the 1960s rate.

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LIMITS TO GROWTH

• In 1972, a report prepared by an influential
  group, The Club of Rome, made similar predictions
  about the availability of resources for an
  expanding population with increasing consumption.
• They suggested that we would run out of food and
  conventional energy before the end of the 1900s.

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TABLE 4. PER CAPITA AVAILABILITY OF RESOURCES
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FOOD SUPPLY

• The FAO (2002) has recently assessed the food
  production using recent estimates of population
  growth.
• Based on present day knowledge and technology,
  the FAO is optimistic that growth in global
  agriculture will be more than sufficient to meet
  world demand of a population of 8 billion in 2030.

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AVAILABILITY OF RESOURCES

• If one of the limiting factors is the amount of
  biological resources available per person, then
  it appears that, given the technologies, at the
  time, the peak of resource availability may have
  already been passed.
• However, it appears that we can expand that
  capacity somewhat. How can we achieve this?

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FORECASTING THE POPULATION

• Age structure (males, females, pre-productive,prod
  uctive and post productive)
• Fertility rate /replacement fertility
• Life expectancy
• Dependency ratio (number of dependents per 100
  people that must be supported during economically
  productive years)

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FUTURE POPULATION TRENDS

• The population of the planet will age much faster
  in the next 50 years with the continuing
  fertility decline and increase in life
  expectancy
• the median age is increasing (1950-23.5,
  1998-26.1, 2050-37.8 est)
• the proportion of less than 15 years old is
  decreasing (1950-34,1998-30,2050-15est)
• The proportion of 60 years old and older
  increased from 8 - 10 between 1950 and 1998

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POPULATION CONTROL

• An extremely sensitive topic
• General strategies education, publicity,
  rewards, penalties, access to contraceptives
  /devices, etc.
• National programs China.

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POPULATION AND ENVIRONMENTAL SUSTAINABILITY

• Not just a national issue - as population
  increases, demands for resources increase,
  pollution and waste increase which in turn
  affects health of human and other populations.
• Overcoming the perception of self-interest? How
  do we achieve this?

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CHALLENGES

• Requires a change in attitude, knowledge and
  affordability.
• Requires empowerment of women, elimination of
  inequality between sexes, and education.
• Recognize that there are cultural and religious
  realities that cannot be easily changed.