2 Key ConceptsHow many people can the earth support?What factors influence the size of the human population?How does a population’s age structures affect its growth or decline?How can we slow human population growth?
3 Core Case Study: Are There Too Many of Us? Estimated 2.4 billion more people by 2050Are there too many people already?Will technological advances overcome environmental resistance that populations face?Should populations be controlled?Will growing populations cause increasedenvironmental stresses?
4 6-1 How Many People Can the Earth Support? 1) 3 major factors account for the population increasea) ability to expand into new habitatsb) Agriculture allows us to feed more peoplec) Sanitation, antibiotics and vaccines2) Death rates dropped causing the increase in population3) Current rate of growth is 1.22% per yeara) Developed 0.1%b) Developing 1.5%
5 4) How many people by 20505) Cultural carrying capacity: optimum level that would allow most people to live in reasonable comfort and freedom without effecting the future generation
6 Science Focus: How Long Can the Human Population Keep Growing? Thomas Malthus and population growth: 1798Humans have altered 83% of the earth’s land surfaceCan the human population grow indefinitely?
7 6-2 What Factors Influence the Size of the Human Population? 1) Population change: same as last chapter2) Crude rates: number of births or deaths per 1000 people in a population
8 3) Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population a) Fertility rate: number of children born to a woman in her lifetimeb) Replacement level fertility rate: ave. number of children that couple must have to replace themselvesc) Current replacement rate: 2.1 in developed and 2.5 in some developingd) At 2.1 rate, the population would continue to grow for 50 years
9 e) Total fertility rate (TFR): ave e) Total fertility rate (TFR): ave. number of children born to women during their reproductive yearsf) Global average 2.6 in 2008 (1.6 developed & 2.8 developing)
10 Case Study: The U.S. Population Is Growing Rapidly Drop in TFR in U.S.Rate of population growth has slowedPopulation still growing and not leveling offFourfold increase since 1900Changes in lifestyle in the U.S. during the 20th century
11 4) Several Factors Affect Birth & Fertility Rates a) Importance of children in labor forceb) Cost of raising & educating a child (290K in US)c) Availability of pension systemsd) Urbanizatione) Educational & employment opportunities for womenf) Infant mortality rate (# of live births who die before age 1)g) Average age at marriageh) Availability of legal abortionsi) Availability of birth controlj) Religious beliefs, traditions and cultural norms
12 5) Several Factors Affect Death Rates a) Largest reason for increased population is a decrease in death ratesb) Better food supplies & distributionc) Better nutrition and medical advancesd) Improved sanitatione) Safer waterf) Indicators of health:1. Life expectance (ave. # of yrs an infant may live)2. Infant mortality rate
13 Several Factors Affect Death Rates (2) g) Why the U.S. infant mortality rate is highInadequate health care for poor women during pregnancy and their infantsDrug addiction among pregnant womenHigh birth rate among teenagersh) Infant mortality rate indicates food supply, nutrition & infectious diseasesi) 4 million infants die of preventable causes per year
14 6) Migration Affects an Area’s Population Size Economic improvementReligious freedomPolitical freedomWarsEnvironmental refugees
15 Case Study: The United States: A Nation of Immigrants Historical role of immigration in the U.S.Legal immigrationIllegal immigration
16 6-3 How Does a Population’s Age Structure Affect Its Growth or Decline? 1) Age structure diagramsa) distribution of males & females by age groupb) Large pre-reproductive will probably growc) Nearly 28% of people were under 15 in 2008
17 Figure 6.13: Global outlook: These charts illustrate population structure by age and sex in less-developed countries and more-developed countries for Question: If all girls under 15 were to have only one child during their lifetimes, how do you think these structures would change over time? (Data from United Nations Population Division and Population Reference Bureau)
18 2) Age-Structures can be used to Make Population and Economic Projections a) Baby boomers added 70 millionb) B.B. make up almost half of the adultsc) They dominate demand for goods & servicesd) Important roles in elections and lawse) Will cause the over 65 to increase starting in 2011f) Their retirement will cause a shortage of workers
19 3) Populations Made Up of Mostly Older People Can Decline Rapidly a) Slow decline is manageableb) Rapid decline can cause severe economic & social problemsc) Strains budgets: medical care, social security, other services, with fewer paying ind) Labor shortages
20 4) Populations Can Decline from a Rising Death Rate: The AIDS Tragedy a) 25 million killed by 2008b) Many young adults die: loss of most productive workersc) Sharp drop in life expectancyd) Loss of the young workerse) International community called upon to1. Reduce the spread of HIV through education and health care2. Financial assistance and volunteers
21 Figure 6.16: Global outlook: Worldwide, AIDS is the leading cause of death for people ages 15–49. This loss of productive working adults can affect the age structure of a population. In Botswana, more than 24% of this age group was infected with HIV in 2008 and about 148,000 people died. This figure shows two projected age structures for Botswana’s population in 2020—one including the possible effects of the AIDS epidemic (red bars), and the other not including those effects (yellow bars). See the Data Analysis Exercise at the end of this chapter for further analysis of this problem. (Data from the U.S. Census Bureau) Question: How might this affect Botswana’s economic development?Fig. 6-16, p. 139
22 6-4 How Can We Slow Human Population Growth? 1) Demographic Transition: Hypothesis of population change tracking death rate decrease & birth rate increase through 4 stages
23 As Countries Develop, Their Populations Tend to Grow More Slowly 2) Demographic trap: countries getting stuck in stage 2 due to various factors (page 133)3) Family planning worksa) has been a major factor in reducing the number of birthsb) has decreased the number of abortionsc) had decreased the number of mother & fetus deathsd) Remaining problems: 42% of pregnancies are unplanned & 201 million couples want to limit the number of children, but lack access in developing countries
24 4) Empowering Women Slows Population Growth a) Women tend to have fewer children if they are educated, hold paying jobs outside the home and live in societies where their rights are not suppressed.b) If daughters are not valued, they are not always educatedc) Teaching women to read decrease populationpoor women who cannot read have 5-7 children compared to 2 or less where most women can.
25 Case Study: Slowing Population Growth in China: the One-Child Policy Encourages fewer childrenGender imbalanceFast-growing economyFace serious resource and environmental problems
26 Case Study: Slowing Population Growth in India Population control: gender biasPovertyMalnutritionEnvironmental problems