The Human Population

Big Idea The size and growth rate of human population has changed drastically over the last 200 years. Those changes have led to profound changes to almost every place on Earth.

Questions to Ponder What is the world’s population? http://www.census.gov/popclock/ http://www.worldometers.info/world-population/ Do the factors that affect other populations affect humans as well? Why or why not?

This is AFTER we factor in deaths Q: If 2.8 humans are born every second, then how many are born each day? 241920 people born each day This is AFTER we factor in deaths over 88,500,000 people born each year

JQ: Which of the following graphs do you think represents the world’s population growth over the next few hundred years (population in vs. time)? Explain. -or-

Studying Human Populations 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 Define demographic transition

Describe what you see on this graph How long did it take to get to 1 billion, then 2, 3, 4, 5, 6? How many people are living today? Did You Know? Basic sanitation was rare even in the medical profession until 1861, when Dr. Ignaz Semmelweis discovered that doctors’ hand washing greatly reduced patient mortality.

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.

Rapid population growth has led to serious environmental problems

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.

2 General Categories of Populations Developed Countries Higher average income Slower population growth Diverse industrial economies Stronger social support systems Developing Countries Lower average incomes Rapid population growth Simple, agriculture-based economies

Exponential Growth Exponential Growth: rapid growth often seen as J-Shaped curve on a graph Is exponential growth sustainable?

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

POPULATION SIZE http://www.worldometers.info/world-population/

Forecasting Population Size Age Structure: the distribution of ages in a population Age Structure Diagrams aka Population Pyramids What is useful about these diagrams?

What do age structure diagrams show? What are the “reproductive years”? Why is that important in forecasting future population growth?

Population Age Structure Rapid Growth Guatemala Nigeria Saudi Arabia Slow Growth United States Australia Canada Male Female Zero Growth Spain Austria Greece Negative Growth Germany Bulgaria Sweden Fig. 10-14 p. 184

QUESTIONS Which “type” of nation is going to see most of the population growth? In which “type” of nation do people live longer lives?

Forecasting Population Size Survivorship: percent of population likely to survive to any given age Survivorship Curves – show how much of the population survives for a given age Type I Wealthy, developed countries Most people live to be very old Type II Similar death rates at all ages Type III Very poor, undeveloped countries Many children die

PROJECTED WORLD POPULATIONS

What causes population to change? Population Changes = (births + immigration) – (deaths + emigration) For world population growth we are only concerned about births and deaths. Many developed countries would have negative population growth without immigration.

Migration: movement INTO (immigration) or OUT of (emigration) an area Population Change = (births + immigration) – (deaths + emigration) Migration: movement INTO (immigration) or OUT of (emigration) an area U.S. growth continues because of both births and immigration

Death rates on the decline… people living longer Population Change = (births + immigration) – (deaths + emigration) Death rates on the decline… people living longer Why? Better hygiene, sewage disposal, clean water, medicines, education, access to food, nutrition

Life Expectancy Life Expectancy: average number of years members of a population are expected to live Improvement in most of world Lower INFANT MORTALITY

Compared to our neighbors

Major changes in U.S. over last 100+ years

Fertility Rates Fertility Rate: number of children born each year per 1,000 women Total fertility rate (lifetime) Replacement level

How have U.S. fertility rates changed? What does this graph show? Total Fertility Rate – average number of births in one woman’s lifetime How have U.S. fertility rates changed?

Fertility and Women Two main factors impact fertility rates worldwide Education level of women (knowledge of family planning) Economic level of women Generally: more education = more wealth = lower fertility rates

Rule of 70: Doubling Time Currently, a city has a population of 10 million. If the population is growing at 10%, when will it reach 20 million? (70/rate = doubling time) What is the growth rate if the population increases from 200 million to 400 million in 14 years ? (70/doubling time = rate)

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, Fertility, Migration, Life Expectancy

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

Diverse World Population Developed Countries US, Canada, Japan, Australia, New Zealand and most of Europe. High Per Capita GDP. (1.2 billion people)

Comparing a Developed Country to a Moderately Developed Developing (Least Developed)

Diverse World Population Developing (lesser developed) 5.2 billion people living with very little 97% of population growth

Percent of World’s 19 Population 81 0.1 Population growth 1.6 85 Wealth and income 85 15 88 Resource use 12 75 Pollution and waste 25 Developed countries Developing countries

World Growth Rates

Strategies for Controlling Growth Public Advertisements Economic Incentives Legal Punishments Empowering Women Investments in Education and Family Planning

Worldwide fertility rates are dropping

Growth Is Slowing but still growing Medium growth rate – fertility rates decline to replacement level by 2050

Review How do developed and developing (less developed) countries compare? What are some strategies for reducing population growth?