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Human Population

Human Population. Envi 201 Spring 2004. Key Concepts. Exponential Growth – Rule of 70 Demographic transition Age structure and population momentum Causes of fertility decline Links between fertility decisions and environment (Dasgupta article). Exponential Growth.

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Human Population

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  1. Human Population Envi 201 Spring 2004

  2. Key Concepts • Exponential Growth – Rule of 70 • Demographic transition • Age structure and population momentum • Causes of fertility decline • Links between fertility decisions and environment (Dasgupta article)

  3. Exponential Growth • Quantity grows by the same relative amount (g) each year • P(next year) = P(this year)* (1+g) • At time t, P = P0 x (1+g)t

  4. Exponential Growth • Quantity grows by the same relative amount each year • Doubling time d is constant

  5. Rule of 70: • Doubling time x growth rate = 70 • Examples:

  6. World Population Growth

  7. World Population Grew Slowly Through 1945…Then accelerated…Then slowed

  8. Trends in Population Growth Worldwide Population Increase and Growth Rate, Five-Year Periods Percent increase per year Millions Source: United Nations, World Population Prospects: The 2002 Revision (medium scenario), 2003.

  9. Growth Rates have Peaked…

  10. Alaska Population: Average Annual Rates of Growth (due to births, deaths, and net migration)

  11. The Demographic Transition • Stage I: high birthrates and death rates • Stage II: continued high birthrates, declining death rates • Stage III: falling birthrates and death rates, eventually stabilizing

  12. Replacement Rate would be 2 children per woman

  13. Population Momentum • Lots of young people • Although each woman may have total fertility = 2 children, • There are many more future mothers than current mothers

  14. Does Alaska have Population Momentum? Native Age Structure

  15. Replacement Rate would be 2 children per woman

  16. Testing the Relationship: • Bangladesh fertility dropped from 7.0 to 3.8 between 1970 and 1998 • Bangladesh income per capita in 1998 is supposed to be $2200 in 1980$…. • Latest HDR says $1602 year 2000$ • Fertility has dropped faster than curve predicts

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