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Chapter 4

Human Populations

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Family Planning in Thailand: A Success Story

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4.1 Past and Current PopulationGrowth are Very Different

• Every second, on average, four or five children are born, somewhere on the earth. In that same second, one or two other people die.

• The U.S. Census Bureau estimates the mid-2010 world population to be about 7 billion people and growing at 1.13 percent per year.

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09/22/10

How the Great Tsunami of 2004

Affected the Human Population

Human Populations Grew Slowly Until Recently

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• For most of our history, humans were not very numerous.

• Populations of early hunting and gathering societies probably numbered only a few million before the invention of agriculture 10,000 years ago.

Population Doubling Time

• Take 70 divided by the percentage growth and you get the number of years it takes for that population to double.

• If our world population were growing at 1% per year (in actuality it is 1.14%) how fast will it double…

70/1=70 years (to go from 8 billion to 16 billion)

09/22/10

4.2 Perspectives on Population Growth

• Does environment or culture control human population growth?

• There have been many opposing views proposed on this subject over the years.

– In 1798, Thomas Malthus hypothesized that human populations would outstrip their food supply and collapse into starvation, crime, and misery.

– A few decades later, Karl Marx presented an opposing view, that population growth resulted from poverty, resource depletion, pollution, and other social ills.

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Is the World Overcrowded?

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What is the Carrying Capacity for Humans?

• Some believe that we are approaching, or may have surpassed, the earth’s carrying capacity.

• Is there a perfect number for earth’s carrying capacity?

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What is eaten in one week!• Germany : The Melander family of Bargteheide

Food expenditure for one week: 375.39 Euros or $500.07

• United States : The Revis family of North Carolina (sure hope most Americanfamilies eat more fresh fruits and vegetables and less junk food than this family.) Food expenditure for one week $341.98

• Italy : The Manzo family of Sicily Food expenditure for one week: 214.36 Euros or $260.11

• Mexico : The Casales family of Cuernavaca Food expenditure for one week: 1, 862.78 Mexican Pesos or $189.09

• Egypt : The Ahmed family of Cairo Food expenditure for one week: 387.85 Egyptian Pounds or $68.53

• Ecuador : The Ayme family of TingoFood expenditure for one week: $31.55

• Bhutan : The Namgay family of Shingkhey VillageFood expenditure for one week: 224.93 ngultrum or $5.03

• Chad : The Aboubakar family of Breidjing CampFood expenditure for one week: 685 CFA Francs or $1.23

• Earth’s human carrying capacity depends in part on how we want to live, and how we want those who follow us to live

Carrying Capacity Analysis

09/22/10

• Joel Cohen, at Rockefeller University reviewed published estimates of the maximum human population size the planet can sustain. The estimates, spanning 300 years of thinking, converged on a median value of 10–12 billion.

• David Pimental from Cornell University states that “By 2100, if current trends continue, 12 billion miserable humans will suffer a difficult life on Earth.”

Technology Increases CarryingCapacity for Humans

• Optimists argue that Malthus was wrong in his predictions of famine and disaster 200 years ago because he failed to account for scientific and technical progress.

• Since then, progress in agricultural productivity, engineering, information technology, commerce, medicine, and sanitation, have made it possible to support approximately 1,000 times as many people per unit area as was possible 10,000 years ago.

• Will we continue to find technological solutions?

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Calculating the Impact of Human Population

• This concept is summarized as the I = PAT formula. Our environmental impacts (I) are the product of our population size (P) times affluence level (A) and the technology level (T).

• Another way to estimate our environmental impacts is to express our consumption choices into the equivalent amount of land required to produce goods and services.

• This gives us a single number, called our ecological footprint, which estimates the relative amount of bioproductive land required to support each of us.

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09/22/10

Population Growth Could Bring Benefits

• More people means larger markets, more workers, and efficiencies of scale in mass production of goods.

• It also means more people to find new resources and better solutions to problems.

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4.3 Many Factors DeterminePopulation Growth

• How many of us are there?

– Demography encompasses vital statistics about people, such as births, deaths, and where they live, as well as total population size.

– We really live in two very different demographic worlds. One of these worlds is poor, young, and growing rapidly, while the other is rich, old, and shrinking in population size.

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We Live in Two Demographic Worlds

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AIDS Affects Population Growth Rates

• In Zimbabwe, Botswana, Zambia, and Namibia, up to 39% of the adult population have AIDS or are HIV positive.

• Without AIDS, the average life expectancy would have been nearly 70 years. Now, with AIDS, life expectancy has dropped to only 31.6 years.

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09/22/10

Politics Affects Population Growth Rates

• In Russia, since the break up of the USSR, population growth rates have taken a drastic downturn.

• Demoralization, increased poverty and political instability have had an impact.

Fertility Varies Among Culturesand at Different Times

• The total fertility rate is the number of children born to an average woman in a population during her entire reproductive life.

• This rate varies according to many factors.

• Living longer has profound social implications.

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World Fertility Rates are Declining

• Zero population growth (ZPG) occurs when births plus immigration in a population just equal deaths plus emigration.

• The world as a whole still has an average fertility rate of 2.6, growth rates are now lower than at any time since World War II.

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Life Expectancy is Rising Worldwide

• Life span is the oldest age to which a species is known to survive.

• Life expectancy is the average age that a newborn infant can expect to attain in any given society.

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Life Expectancy is Related to Income

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Living Longer has Profound Social Implications

• These histograms can be used to determine thedependency ratio, the number of nonworking compared with working individuals in a population.

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Age Class Histograms

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Projection of Shifting Dependency Ratios

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4.4 Fertility is Influenced by Culture• A number of social and economic pressures

affect decisions about family size, which in turn affects the population at large.

• Factors that increase people’s desire to have babies are called pronatalist pressures.

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Education and Income Affect the Desire for Children

• Highly developed countries

– Higher education and personal freedom affect women to not have children.

– The desire to spend time and money on other priorities limits the number of children.

• Less-developed countries

– Feeding and clothing is minimally expensive, adding one more child is negligible.

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4.5 A Demographic Transition CanLead to Stable Population Size

• Demographic transition is a typical pattern of falling death rates and birth rates due to improved living conditions that usually accompanies economic development.

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Stage I

• Poor conditions mean high mortality rates and high births

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Stage II

• Economic development in Stage II brings better jobs, medical care, sanitation, and a generally improved standard of living, and death rates often fall very rapidly.

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Stage III

• Note that populations grow rapidly during Stage III when death rates have already fallen but birth rates remain high.

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Stage IV

• Stage IV represents conditions in developed countries, where the transition is complete and both birth rates and death rates are low, often a third or less than those in the predevelopment era.

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Two Ways to Completethe Demographic Transition

• The Indian states of Kerala and Andra Pradesh exemplify two very different approaches to regulating population growth.

• In Kerala, providing an equal share of social benefits to everyone through redistribution of resources is seen as the key to family planning.

• The leaders of Andra Pradesh, on the other hand, have adopted a strategy of emphasizing birth control; providing economic rewards for reducing births and punishment for exceeding limits.

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Improving Women’s Lives HelpsReduce Birth Rates

• A broad consensus at a conference of many countries in 1994 resulted in the agreement that the following will help reduce birth rates worldwide:

– responsible economic development

– education and empowerment of women

– high-quality health care with access to family planning services

• Also, more opportunities for education, land reform, political rights, and the opportunity to earn an independent income, will help reduce birth rates

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4.6 Family Planning Gives Us Choices

• Family planning allows couples to determine the number and spacing of their children.

• Birth control usually means any method used to reduce births including celibacy, delayed marriage, contraception, and methods that prevent embryo implantation and other methods like induced abortions.

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Conclusion

• A few decades ago, we were warned that a human population explosion was about to engulf the world.

• However, birth rates have fallen, almost everywhere, and most demographers now believe that we will reach an equilibrium around 9 billion people in about 2050.

• How, or if we should carry out family planning and utilize birth control remains controversial.

• How many humans our planet can support on a long-term basis also remains a vital question.

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