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Chapter 8 Human

Population

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China’s One-Child Policy• In 1970, the average Chinese woman had

about six children. • Since 1979, China has used a system of

rewards and punishments to enforce a one-child limit to slow population growth.

• In 2005, there were 32 million more males than females in China under the age of 20

Write About It Is it ethical for governments to limit or encourage human population growth?

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• Why did it take so long to reach 1 billion?

• Why do you think it took off around the late 1880s?

Interesting Fact: Of all the humans ever born, approximately 6-7% are alive today.

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Studying Human Populations

Demography: the study of human population

How many people live where?

How long are you expected to live?

How many children are you likely to have.

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Demography• Population size: Number of people

• Population density: Number of people living per mi2 (or per km2)

• Population distribution: How people are distributed within an area

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Exponential Growth

Exponential Growth: rapid growth often seen as J-Shaped curve on a graph

Can that growth continue?

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Forecasting Population Size

Will new schools be needed?

Should we be building more housing?

Should farming practices be improved?

Predictions like this often wrong because human behavior changes

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Forecasting Population Size

Age Structure: the distribution of ages in a population

Age Structure Diagrams also known as population pyramids

What is useful about these diagrams?

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• What are these age-structure diagrams showing?

• What are the “reproductive years” Why is that important in forecasting future population growth?

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• Which “type” of countries are going to see most of the population growth?

• Which “type” of countries do people live longer lives?

• Survivorship: percent of population likely to survive a given age

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Fertility and Women Two main factors

impact fertility rates worldwide

Education level of women (knowledge of family planning)

Economic level of women

Generally, on average, more education, more wealth = lower fertility rates

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• What does this graph show?

• How has U.S. fertility rates changed?

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Migration: movement INTO – immigration

or OUT of emigration

an area

Population

Change = (births + immigration) – (deaths + emigration)

U.S. growth continues because of both births and immigration

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Death rates on the decline… people living longer

Why?

Population

Change = (births + immigration) – (deaths + emigration)

Better hygiene, sewage disposal, clean water, medicines, education, access to food, nutrition

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Demographic TransitionEvery Country Goes

Through It

Explain what you see on this chart

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• Stage 1 : High Birth AND Death rates = little population change

• Stage 2 : Death Rates Fall, Birth Rates Still High = Population Growth

• Stage 3: Death Rates Low, Birth Rates Drop = Population Growth Slows

• Stage 4: Death Rates Low, Birth Rate Low = Population Declines

DESCRIBE EACH STAGE: WHAT DO YOU SEE?

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Calculations

A town currently has a population of 20 people. If 10 people are born, 8 people die, 3 immigrate and 1 emigrate, what is the population?

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Calculations

USA currently has a population of 320,000,000 people. If 5,000,000 people are born, 2,000,000 people die, 200,000 immigrate and 50,000 emigrate, what is the population?

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Rule of 70: Doubling Time

1. Currently, a city has a population of 10 million. When will it reach 20 million if the population is growing at 10% per year (growing 10% every year)?

2. How long will it take a population to go from 200 to 400 if it grows at 5% a year?

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Rule of 70: Doubling Time

1. Currently, a city has a population of 10 million. When will it reach 20 million if the population is growing at 10% per year (growing 10% every year)?

2. How long will it take a population to go from 200 to 400 if it grows at 5% a year?

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Review

Describe how the size and growth rate for human population has changed over history

What factors lead to population changes

Analyze populations using Age Structure Diagrams

Terms: Demography, Age Structure, Survivorship, Fertility, Migration, Life Expectancy

23Ages 0-14Ages 0-14 Ages 15-44Ages 15-44 Ages 45-85+Ages 45-85+

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Slow GrowthUnited States

AustraliaCanada

Slow GrowthUnited States

AustraliaCanada

MaleMale FemaleFemale

Zero GrowthSpainAustriaGreece

Zero GrowthSpainAustriaGreece

Negative GrowthGermanyBulgariaSweden

Negative GrowthGermanyBulgariaSweden

Population Age StructurePopulation Age Structure

Fig. 10-14 p. 184Fig. 10-14 p. 184

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Problems With Rapid Growth

Lack of infrastructure to support population

Water supplies Sewers Roads Schools Powerplants Hospitals Housing

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Problems With Rapid Growth

Using up resources too quickly

Water supplies Food Supplies,

Vegetation Wood/fuels : wood

supplies critical to life in many regions

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Problems With Rapid Growth

Unsafe water supplies

Sewage mixing with water supplies

Cholera, Dysentery, Typhoid

1 Billion lack clean water

3 million/yr die

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Clean Water Lacking

If the millions of women who haul water long distances had a faucet by their door, whole societies could be transformed.

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Problems With Rapid Growth

Land becomes scarce Arable land : land

that can grow crops

Tradeoffs made : agriculture, housing, natural habitats

Which do you think typically wins out?

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Problems With Rapid Growth

Urbanization: movement of people from rural areas to cities

Much of world is going through

Increased demand on infrastructure

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Problems With GrowthIn U.S.Suburban sprawl:

work in cities live in suburbs

Decay of inner cities

Increased traffic Loss of farmland Decreased wildlife

habitat

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Comparing a developed country

to

Moderately Developed

to

Developing (lesser developed)

Did You Know? On average, 1 American consumes as much natural resources as 5 Chinese or 13 Pakistanis.

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Diverse World Population

Developing (lesser developed)

5.2 billion people living with very little 97% of population

growth.

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Percent of World’s

Developingcountries

Developedcountries

Population

Populationgrowth

Wealth andincome

Resourceuse

Pollutionand waste

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81

0.1

1.6

85

15

88

12

75

25

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Growth Is Slowingbut still growing