Population Dynamics - History

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• Population Dynamics - History
• Thomas Malthus (1766-1834)
• English parson
• Became concerned that unrestricted population
  growth would cause demand to exceed availability
  of resources
• Predicted widespread poverty and famine
• Global population lt 1 billion
• Malthusians - People who forecast disaster due to
  overpopulation
• Many of Malthus predictions did not occur
• Agricultural improvements (did not foresee)
• Birth control (rejected on moral grounds)

PopClock
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• Population Dynamics - History
• Demographic Transition
• Theory developed to explain human population
  dynamics in response to economic development
• Cohen Four Stages
• High birth death rates (nearly equal but
  variable) ? Growth rate low
• Death rate falls and becomes less variable, birth
  rate still high ? Growth rate rises, population
  increases. Mortality transition
• Birth rate drops, death rate remains low or
  declines, growth rate slows, population
  increases. Fertility transition
• Low birth death rates (nearly equal, not
  variable), growth rate low or negative,
  population larger than before (1)
• This process has occurred in many developed
  nations
• United States, Canada, Japan, Western Europe
• Mortality and fertility transitions typically due
  to greater affluence, improved health care,
  changing social expectations, etc.

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• Population Dynamics - History
• Demographic Transition
• In recent years death rates in many developing
  nations have decreased
• Status of the social and economic changes that
  will supposedly lead to stable populations is
  unclear
• Some neo-Malthusians pessimistic that transition
  to lower birth rates and stable populations will
  occur
• Garrett Hardin - Lifeboat Ethics
• Barry Commoner - Anti-Malthusian
• Main cause of environmental degradation is
  inappropriate use of technology, not simple
  population growth
• Ecologically sound development more important
  than population control

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• Population Dynamics - Theory
• Background
• Understanding human population dynamics requires
  understanding population theory
• Earth is a closed system (no immigration/emigratio
  n)
• Population size is dynamic equilibrium between
• Biotic potential
• Environmental resistance
• Two basic growth models
• Density-independent (exponential) growth
• Density-dependent (logistic) growth

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• Population Dynamics - Theory
• Density-Independent Growth
• Population growth with unlimited resources
• In nature, usually occurs rarely and briefly
• Limited by maximum reproduction rate for a
  species
• Inversely related to generation time
• Ex - Higher for mouse than human

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• Population Dynamics - Theory
• Density-Independent Growth
• Not sustainable indefinitely in the real world
• Assumes/Requires unlimited resources
• Increasing population density limits ability of
  individuals to acquire resources
• Density affects/limits population growth rate
• Density-Dependent Growth
• Based on idea that a given environment only can
  support a limited number of individuals
• Carrying capacity
• Population growth described by logistic growth
  model
• Environmental resistance increases as population
  size increases

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• Population Dynamics - Trends
• Demographics
• Global population reached 6 billion in Oct 1999
• Most population growth currently taking place in
  developing nations
• Developing nations contain 80 of global
  population
• Percentage of global population growth in
  developing nations
• 1950 85
• Today 99

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• Population Dynamics - Trends
• Total Fertility Rate (TFR)
• TFR Fecundity
• 2.0 Replacement level fertility
• Global TFR
• 1950 5.0
• 2007 2.60 (48 decrease)
• Africa 4.73 (Mali 7.38, Niger 7.37)
• Asia 2.41 (India 2.81, China 1.75)
• N America 2.26 (Canada 1.61, Mexico 2.39,
  USA 2.09)
• Europe 1.45 (Lithuania 1.21, Italy 1.29,
  Spain 1.29)

Source U.S. Census Bureau
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• Population Dynamics - Trends
• Infant Mortality Rate (IMR)
• Global IMR
• 1950 156 deaths per 1000 births (15.6)
• 2007 44.0 deaths per 1000 births (4.40)
• 72 decrease
• Europe 0.76
• Africa 8.03

Source U.S. Census Bureau
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• Population Dynamics - Trends
• Birth and Death Rates
• 1950
• Birth rate 37 per 1000 people per year
• Death rate 20 per 1000 people per year
• Growth 17 per 1000 people per year 1.7
• 2007
• Birth rate 20.2 per 1000 people per year
• Death rate 8.4 per 1000 people per year
• Growth 11.8 per 1000 people per year 1.18
• Developed nations 0.22 (0.06 B-D 0.16 I)
• Developing nations 1.38 (1.43 B-D 0.05 E)

Source U.S. Census Bureau
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• Population Dynamics - Trends
• Age and Life Expectancy
• Median Age
• World 28.0 years
• Developed nations 39.2 years
• Europe 39.8 years
• N. America 32.0 years
• Developing nations 25.8 years
• Africa 19.3 years
• Life Expectancy
• 1950 46 years
• 2007 65.7 years
• Africa 51.9 years (Swaziland 32.2 years)
• Europe 74.8 years (Andorra 83.5 years)
• N. America 75.9 years (USA 78.0 years)

Source U.S. Census Bureau
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• Population Dynamics - Trends
• Population Projections - UN
• Low Variant (TFR ? 1.35 by 2050)
• 2050 7.68 billion
• 2150 3.2 billion
• Medium Variant (TFR ? 1.85 by 2050)
• 2050 9.08 billion
• 2150 9.7 billion
• High Variant (TFR ? 2.35 by 2050)
• 2050 10.65 billion
• 2150 24.8 billion
• Constant Variant (TFR 2.59)
• 2050 11.66 billion
• 2150 51.2 billion

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United Nations Population Division
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• Population Environmental Effects
• Ehrlich Earth can support a larger population
  of cooperative, far-sighted, vegetarian pacifist
  saints than of competitive, myopic, meat-eating,
  war-making typical human beings. All else being
  equal, Earth can hold more people if they have
  relatively equal access to the requisites of a
  decent life than if the few are able to
  monopolize resources and the many must largely do
  without. The problems of population, social and
  economic inequity, and environmental
  deterioration are thus completely intertwined.

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• Population Environmental Effects
• Not all humans impact the environment equally
• Industrialized nations currently house 22 of the
  worlds population but consume
• 60 of food
• 70 of energy
• 75 of metals
• 85 of wood
• Generate 75 of CO2 emissions

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• Population Environmental Effects
• I PAT (Ehrlich and Holdren)
• I Environmental Impact of nation
• P Population
• A Affluence (reflects consumption)
• T Technology (reflected in pollution)
• Ex Changes in CFC emissions related to
  technology, not population
• Developments in technology historically not
  directed toward environmental preservation