Population Dynamics - History

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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
• Per-capita growth rate (r)
• r b - d (per-capita birth rate - death rate)
• r gt 0 population growing
• r lt 0 population shrinking
• r 0 ZPG

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• Population Dynamics - Theory
• Background
• Instantaneous growth rate of a population may be
  represented by dN/dt rN
• dN/dt - Change in population size over time
• r - Per-capita growth rate
• N - Population size
• Two basic growth models
• Density-independent growth
• Density-dependent 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 per-capita growth rate for a
  species (rmax)
• rmax inversely related to generation time
• Ex - Higher for mouse than human
• Population growth rate described by
• dN/dt rmaxN
• Exponential growth

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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

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• Population Dynamics - Theory
• Density-Dependent Growth
• Based on idea that a given environment only can
  support a limited number of individuals
• Carrying capacity (K)
• Population growth described by logistic growth
  model
• dN/dt rmaxN (1-N/K)
• Environmental resistance (N/K) increases as N
  increases

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• Population Dynamics - Trends
• Demographics
• Global population reached 6 billion in Oct 1999
  and 7 billion in Oct 2011
• 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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Roberts 2011
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UN Population Division
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• Population Dynamics - Trends
• Total Fertility Rate (TFR)
• TFR Fecundity
• 2.0 Replacement level fertility
• Global TFR
• 1950 5.0
• 2010 2.45 (51 decrease)
• Africa 4.37 (Niger 7.19, Somalia 6.40)
• Asia 2.18 (India 2.73, China 1.64)
• N America 2.04 (Canada 1.65, Mexico 2.41,
  USA 2.07)
• Europe 1.59 (Bosnia 1.18, Germany 1.36)
• PRB Map

Source UN Population Division
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UN Population Division
Roberts 2011
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• Population Dynamics - Trends
• Infant Mortality Rate (IMR)
• Global IMR
• 1950 156 deaths per 1000 births (15.6)
• 2010 43 deaths per 1000 births (4.30)
• 72.4 decrease
• Europe 0.7
• Africa 7.50

Source UN Population Division
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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
• 2010
• Birth rate 19.4 per 1000 people per year
• Death rate 8.3 per 1000 people per year
• Growth 11.1 per 1000 people per year 1.11
• Developed nations 0.23 (0.07 B-D 0.16 I)
• Developing nations 1.28 (1.33 B-D 0.05 E)

Source UN Population Division
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• Population Dynamics - Trends
• Age and Life Expectancy
• Median Age
• World 29.4 years (2011)
• Developed nations 39.7 years
• Europe 40.2 years
• N. America 36.9 years
• Developing nations 26.8 years
• Africa 19.7 years
• Life Expectancy
• 1950 46 years
• 2010 68.9 years
• Africa 56.0 years (Swaziland 48.7 years)
• Europe 76.1 years (Andorra 83.5 years)

Source UN Population Division
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Roberts 2011
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• Population Dynamics - Trends
• Population Projections - UN
• Low Variant (TFR 2.45 ? 1.55 by 2100)
• 2050 8.1 billion, 2100 6.2 billion
• Medium Variant (TFR 2.45 ? 2.03)
• 2050 9.3 billion, 2100 10.1 billion
• High Variant (TFR 2.45 ? 2.51)
• 2050 10.6 billion, 2100 15.8 billion
• Constant Variant (TFR 2.45 ? 4.44)
• 2050 10.9 billion, 2100 26.8 billion

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Roberts 2011