1 Principles of Environmental Science Inquiry and Applications Third Edition Cunningham Chapter 4 Lecture Outlines* *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Human Populations Chapter 4

3 Outline: Population Doubling Times Malthus vs. Marx Role of Technology Two Demographic Worlds Fertility and Birth Rates Mortality and Death Rates Population Growth Factors Demographic Transition Future of Population Growth

4 POPULATION GROWTH For most of human history, humans have not been very numerous compared to other species.  It took all of human history to reach 1 billion.  150 years to reach 3 billion.  12 years to go from 5 to 6 billion. - Human population tripled during the twentieth century.

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6 Human Population History

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8 Population Doubling Times Rule of Thumb:  In exponentially growing populations: - 70/annual % growth = Doubling Time  70/2.0% = 35 years

Table 04.01

10 LIMITS TO GROWTH Thomas Malthus (1798) argued human populations tend to increase exponentially while food production is plentiful.  Humans inevitably outstrip food supply and eventually collapse. - Human population only stabilized by positive checks. - Humans are too lazy and immoral to voluntarily regulate birth rates.

Figure 04.03

12 Karl Marx Population growth is a symptom rather than a root cause of poverty and other social problems.  Real causes of these problems are exploitation and oppression. - The way to slow population growth and alleviate many social problems is through social justice.

13 Malthus and Marx Today Neo-Malthusians - Believe we are approaching, or have already surpassed, the Earth’s carrying capacity.  We should make over-population issues our first priority. Neo-Marxists - Believe eliminating oppression and poverty through social justice is the only solution to the population problem.  Wealth and resource distribution must be addressed.

14 The Role of Technology Technological optimists argue that Malthus was wrong in his predictions because he failed to account for scientific progress.  Current burst of growth was stimulated by the scientific and industrial revolutions.

15 Can More People be Beneficial? More people mean larger markets, more workers, and increased efficiency due to mass productions. Greater numbers also provide more intelligence and enterprise to overcome problems.  Human ingenuity and intelligence.

16 HUMAN DEMOGRAPHY Demography - Encompasses vital statistics about people such as births, deaths, distribution, and population size.  October 12, 1999, UN officially declared the human population reached 6 billion. - Estimation at best.

17 Estimated Human Population Growth

18 Two Demographic Worlds First is poor, young, and rapidly growing.  Less-developed countries. - Africa, Asia, Latin America - Contain 80% of world population, and will account for 90% of projected growth. Second is wealthy, old, and mostly shrinking.  North America, Western Europe, Japan - Average age is about Populations expected to decline.

Table 04.02

Figure 04.05

20. Demographic transition:accompanies economic development & stabilization. 21

Figure 04.06

23 Fertility and Birth Rates Crude Birth Rate - Number of births in a year per thousand. (Not adjusted for population characteristics) Total Fertility Rate - Number of children born to an average woman in a population during her reproductive life. Zero Population Growth - Occurs when births plus immigration in a population just equal deaths plus emigration.

24 Mortality and Death Rates Crude Death Rate - Number of deaths per thousand persons in a given year.  Poor countries average about 20 while wealthier countries average about 10 per 1,000 people. - Some rapidly growing countries have very low crude death rates compared to slower growing countries, due to a higher proportion of young people in the population.

24. Ex of r of slow growth= .0019 or 0.19% 25

26 Life Span and Life Expectancy Life Expectancy - Average age a newborn can expect to attain in any given society.  Worldwide, average has risen from 40 to 65.5 over the past century. - Greatest progress has been in developing countries.  Annual income and life expectancy are strongly correlated up to about $4, (U.S.) per person.

27 Fig. 4.7 Life Expectancy

Table 04.03

29 Demographic Implications of Living Longer A population growing rapidly due to natural increase has more young people than a stationary population. Natural Increase  (Crude Birth Rate - Crude Death Rate)  Both rapidly and slowly growing countries can have a problem with dependency ratio. - The number of non-working compared to working individuals in a population.

30 Age Structure Diagrams

31 Population Growth : Opposing Factors Pronatalist Pressures  Factors that increase the desire for children. - Source of pleasure, pride, comfort. - Source of support for elderly parents. - Current source of family income. - Social Status - Replace members in society as they die.  Boys frequently valued more than girls.

Figure 04.10

33 Birth Reduction Pressures Higher education and personal freedom for women often result in decisions to limit childbearing.  When women have more opportunities to earn a salary, they are less likely to have children: therefore birthrates decrease as development increases.  Education and socioeconomic status are usually inversely related to fertility in wealthier countries.

34 Birth Reduction Pressures Cont’d In developing countries, higher income often means families can afford more children, thus fertility often increases. In less-developed countries, adding another child to a family usually does not cost much, while in developed countries, raising an additional child can carry significant costs.

Figure 04.14

36 DEMOGRAPHIC TRANSITION Model of falling death rates and birth rates due to improved living conditions accompanying economic development.  Pre-Developed Country - Poor conditions keep death rates high, thus birth rates are correspondingly high.  Economic Development brings better conditions and standard of living thus death rates fall. Birth rates stay constant or even rise.

37 United States Birth Rate

38 DEMOGRAPHIC TRANSITION CONT’D Eventually, birth rates begin to fall.  Populations grow rapidly in time between death rates and birth rates fall. Developed Countries - Transition is complete and both death and birth rates are low and population is in equilibrium.

Figure 04.09

40 Demographic Transition

42. Replacement level fertility: Current fertility:

42 Optimism or Pessimism Some demographers believe the demographic transition is already taking place in developing countries, and world population should stabilize during the next century. Others argue that many poorer countries are trapped in the middle phase of transition, and their populations are growing so rapidly that human demands exceed sustainable resource yields.

43 Social Justice Still other demographers believe that in order for the demographic transition model to work, resources must be distributed more equitably.  The world has enough natural resources, but inequitable social and economic systems cause maldistribution.

Figure 04.10

45 FAMILY PLANNING Family Planning allows couples to determine the number and spacing of their children. Birth Control - Any method used to reduce births.  Traditional Methods - Long breast-feeding, taboos against intercourse while breast-feeding, celibacy, folk medicines, abortion, infanticide.

46 United States Birth Rate

Current Methods 48. Contraceptive is usually by women because men fear hormone change and repressed sex drive. 47

48 Birth Control Current Methods  Avoidance of sex during fertile periods.  Mechanical barriers preventing contact between sperm and egg.  Surgical prevention of sperm or egg release.  Chemical prevention of sperm or egg maturation, release, or implantation.  Physical barriers to implantation.  Abortion

Figure 04.16

Figure 04.17

Figure 04.18

iveFigure 04.01

iveFigure 04.02

54 FUTURE OF HUMAN POPULATIONS Most demographers believe the world population will stabilize sometime during the next century.  Projections of maximum population size: - Low 8billion - Medium 9.3 billion - High 13 billion Stabilize by decreasing child mortality, BUT we are still growing.

55 Summary: Population Doubling Times Malthus vs. Marx Role of Technology Two Demographic Worlds Fertility and Birth Rates Mortality and Death Rates Population Growth Factors Demographic Transition Future of Population Growth

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