1. Population Dynamics and Growth

2. Exponential Growth Time (t) Population size (N) -ideal habitat -maximum reproduction -unlimited resources Increase often followed by crash

3. 2,000 1,500 Number of reindeer 19101920193019401950 Year 1,000 500 Reindeer on an Alaskan island

4. 5,000 4,000 3,000 2,000 1,000 500 Number of moose 100 90 80 70 60 50 40 30 20 10 0 1900191019301950197019902000 1999 Year Number of wolves Moose population Wolf population Moose and wolves on Isle Royale

5. Logistic Growth Time (t) Population size (N) K -accelerating, decelerating Carrying capacity -growth slows as population size approaches carrying capacity -number that environment can support indefinitely Carrying capacity set by limiting factor

6. 2.0 1.5 1.0.5 Number of sheep (millions) 180018251850187519001925 Year Sheep in Tasmania

7. Human population growth -exponential or logistic?

8. -appears exponential -history may suggest logistic -periods of rapid growth followed by stability

9. Human population growth -exponential or logistic? Cultural evolution -tool-making revolution -agricultural revolution -industrial (technological) revolution

10. Carrying capacity for humans Set by: -famine -disease -warfare Will these become more common as population approaches carrying capacity?

11. Population Demographics  What affects human population size and growth rate?  What affects human population size and growth rate? 1) Birth rate and death rate 2) Migration rate 3) Fertility rate 4) Age structure 5) Average marriage age 1) Birth rate and death rate 2) Migration rate 3) Fertility rate 4) Age structure 5) Average marriage age

12. Factors Affecting Human Population Size  Population change equation  Zero population growth (ZPG)  Birth rate (number/1000 people/year)  Death rate (number/1000 people/year) Population Change Population Change = = (Births + Immigration) – (Deaths + Emigration)

13. Birth and death rates  U.S. - 16 and 9 (7 or 0.7%)  Rwanda - 52 and 18 (34 or 3.4%) 32 30 28 26 24 22 20 18 16 14 0 Births per thousand population 19101920193019401950196019701980199020002010 Year Demographic transition Depression End of World War II Baby boomBaby bustEcho baby boom  World - 26 and 9 (17 or 1.7%)

14. Infant deaths per 1,000 live births <10 <10-35 <36-70 <71-100 <100+ Data not available Factors Affecting Death Rate  Life expectancy  Infant mortality rate (IMR)

15. Rate of Natural Increase Developed Countries 50 40 30 20 10 0 1775 1800 185019001950 2000 2050 Rate of natural increase Crude birth rate Crude death rate Rate of natural increase = crude birth rate–crude death rate Developing Countries 50 40 30 20 10 0 1775 1800 185019001950 2000 2050 Rate per 1,000 people Crude birth rate Rate of natural increase Crude death rate Year © 2004 Brooks/Cole – Thomson Learning

16. Natural Rate of Increase <1% 1-1.9% 2-2.9% 3+% Data not available Annual world population growth 1% - triple in 100 years 2% - 7X in 100 years

17. Migration Rates  Affect regional populations  e.g., United States  Net gain of 4/1000 people/year  Add to 7 from BR - DR = 11 (1.1%)

18. Fertility Rates  Average number of children born to a woman during her childbearing years (ages 15-44)  Average number of children born to a woman during her childbearing years (ages 15-44)  Replacement level fertility rates for ZPG  Replacement level fertility rates for ZPG  Total fertility rates

19. Fertility Rates  Replacement level fertility rates for ZPG - developed countries - 2.1/woman - developing countries - 2.5 - total world - 2.3-2.4  Replacement level fertility rates for ZPG - developed countries - 2.1/woman - developing countries - 2.5 - total world - 2.3-2.4

20. Fertility Rates  Total fertility rates - developed countries – 1.6 (U.S. 2.2) - developing countries – 2.9 (older values:Rwanda-8.5, Kenya-8.0) - total world – 2.7  Total fertility rates - developed countries – 1.6 (U.S. 2.2) - developing countries – 2.9 (older values:Rwanda-8.5, Kenya-8.0) - total world – 2.7

21. Births per woman < 2 2-2.9 3-3.9 4-4.9 5+ No Data Fertility Rates

22.  Time lag to ZPG - about 3 generations (~70 years) required to achieve ZPG once replacement level fertility rates are reached  Time lag to ZPG - about 3 generations (~70 years) required to achieve ZPG once replacement level fertility rates are reached

23. Ages 0-14 Ages 15-44 Ages 45-85+ Rapid Growth Guatemala Nigeria Saudi Arabia Rapid Growth Guatemala Nigeria Saudi Arabia Slow Growth United States Australia Canada Slow Growth United States Australia Canada Male Female Zero Growth Spain Austria Greece Zero Growth Spain Austria Greece Negative Growth Germany Bulgaria Sweden Negative Growth Germany Bulgaria Sweden Population Age Structure

24. Average Marriage Age  or age at birth of first child  Higher marriage age leads to reduced reproductive period, which leads to lower fertility rates  Higher marriage age leads to reduced reproductive period, which leads to lower fertility rates

25. Average Marriage Age  Current U.S. marriage age - 24 (F)  Reduces 30-year reproductive period (15-44) to 21-year reproductive period (24-44) - 30% reduction  Reduces 30-year reproductive period (15-44) to 21-year reproductive period (24-44) - 30% reduction  Reduces 15-year prime reproductive period (15-29) to a 6-year prime reproductive period (24-29) - 60% reduction  Reduces 15-year prime reproductive period (15-29) to a 6-year prime reproductive period (24-29) - 60% reduction  Expectation: >25 needed to affect fertility rate

26. Current Needs for Large Families  Increased income  High infant mortality  Support for elderly  Few opportunities for women outside the home  Few opportunities for women outside the home  Family planning unavailable

27. Can population growth be slowed?  Family planning  Economic development

28. Family Planning  Goal: help people have only as many children as they want, when they want them  Goal: help people have only as many children as they want, when they want them

29. Family Planning  Contraceptive methods - pills, devices, abortion (1 in 5 pregnancies terminated by abortion in world, 1 in 3 in U.S.)  Contraceptive methods - pills, devices, abortion (1 in 5 pregnancies terminated by abortion in world, 1 in 3 in U.S.)

30. Family Planning  Economic incentives, disincentives - direct incentives for contraceptive use, etc. - delayed incentives - old-age pensions - health insurance - free education for small families - penalties - extra taxes, reduce/withhold benefits for too many children  Economic incentives, disincentives - direct incentives for contraceptive use, etc. - delayed incentives - old-age pensions - health insurance - free education for small families - penalties - extra taxes, reduce/withhold benefits for too many children

31. Family Planning  Increased women’s rights - jobs - education - shown to lead to lower fertility rates  Increased women’s rights - jobs - education - shown to lead to lower fertility rates

32. Economic Development  Goal: encourage people to want fewer children  Goal: encourage people to want fewer children  Stimulating economy influences demographics - demographic transition model - reduction in birth rate is ultimate goal  Stimulating economy influences demographics - demographic transition model - reduction in birth rate is ultimate goal

33. The Demographic Transition Low High Relative population size Birth rate and death rate (number per 1,000 per year) Birth rate and death rate (number per 1,000 per year) 80 70 60 50 40 30 20 10 0 0 Stage 1 Preindustrial Stage 1 Preindustrial Stage 2 Transitional Stage 2 Transitional Stage 3 Industrial Stage 3 Industrial Stage 4 Postindustrial Stage 4 Postindustrial Low growth rate Low growth rate Increasing Growth growth rate Increasing Growth growth rate Very high growth rate Very high growth rate Decreasing growth rate Decreasing growth rate Low growth rate Low growth rate Zero growth rate Zero growth rate Negative growth rate Negative growth rate Birth rate Total population Death rate Time

34. Case Study: Slowing Population Growth in China (1.3 billion people)  Economic incentives  Free medical care  Preferential treatment  Intrusive and coercive  Locally administered Generally positive results: begun in 1972

35. China’s Program: The Details - birth rate cut in half  Encourage later marriage (24-28 F, 26-30 M)  Family planning decentralized  Pledge benefits, penalties  Mandatory sterilization for >2 children  Free contraceptives (IUD), sterilization abortion  Free contraceptives (IUD), sterilization abortion  83% participation, fertility rate 5.7 to 1.7

36. Case Study: Slowing Population Growth in India (1.1 billion people)  Poor planning (centralized)  Bureaucratic inefficiency  Low status of women (desire for male child)  Low status of women (desire for male child)  Extreme poverty  Lack of support Generally disappointing results: begun in 1950s Generally disappointing results: begun in 1950s

37. India’s Program: The Details - no effect  Only 20% participation  Majority rural, illiterate (high fertility rate, high infant mortality)  Majority rural, illiterate (high fertility rate, high infant mortality)  36% of population <15 years of age  Mid-1970s - voluntary sterilization!  1978 raised minimum marriage age  Education to rural areas via satellite

38. Cutting Global Population Growth  Family planning  Reduce poverty  Elevate the status of women