1. I. I.Population Dynamics - History B. B.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

2. II. II.Population Dynamics - Theory A. A.Background Understanding human population dynamics requires understanding population theory Earth is a closed system (no immigration/emigration) Population size is dynamic equilibrium between Biotic potential Per-capita growth rate (r) r = b - d (per-capita birth rate - death rate) r > 0 population growing r < 0 population shrinking r = 0 ZPG

3. II. II.Population Dynamics - Theory A. A.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

4. II. II.Population Dynamics - Theory B. B.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 (r max ) r max inversely related to generation time Ex - Higher for mouse than human Population growth rate described by dN/dt = r max N Exponential growth

6. II. II.Population Dynamics - Theory B. B.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

7. II. II.Population Dynamics - Theory C. C.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 = r max N (1-N/K) Environmental resistance (N/K) increases as N increases

13. III. III.Population Dynamics - Trends A. A.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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15. UN Population Division

16. III. III.Population Dynamics - Trends B. B.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

17. UN Population DivisionRoberts 2011

18. III. III.Population Dynamics - Trends C. C.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

19. III. III.Population Dynamics - Trends D. D.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

20. III. III.Population Dynamics - Trends E. E.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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22. III. III.Population Dynamics - Trends F. F.Population Projections - UN 1. 1.Low Variant (TFR: 2.45  1.55 by 2100) 2050 – 8.1 billion, 2100 – 6.2 billion 2. 2.Medium Variant (TFR: 2.45  2.03) 2050 – 9.3 billion, 2100 – 10.1 billion 3. 3.High Variant (TFR: 2.45  2.51) 2050 – 10.6 billion, 2100 – 15.8 billion 4. 4.Constant Variant (TFR = 2.45  4.44) 2050 – 10.9 billion, 2100 – 26.8 billion

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