1. The Human Population and Its Impact
Chapter 6

2. World Population www.census.gov/main/www/popclock.html

3. World Population Distribution

4. World Population Density

5. World Land Area

6. World Population Density
The size of each territory shows the relative proportion of the world's population living there.

7. World Population Growth Rates

8. World Population Growth
Pop. Size...
Reached in...
Interval between next
1 Billion people...
1 Billion
1804
2 Billion
1927
123 years later
3 billion
1960
33 years later
4 Billion
1974
14 years later
5 Billion
1987
13 years later
6 Billion
1999
12 years later
7 Billion
2011
8 Billion
2028
17 years later
9 billion
2050
22 years later

9. Core Case Study: Are There Too Many of Us?
The world’s population is projected to increase from 7 billion to 9.3 billion between 2012 and 2050.
Much of the world’s population growth occurs in rapidly developing countries like China and India.

10. Core Case Study: Are There Too Many of Us?
Some argue that the planet has too many people.
Some feel that the world can support billions of more people due to technological advances.
There is a constant debate over the need to reduce population growth.
Must consider moral, religious, and personal freedom.
The debate over interactions among population growth, economic growth, politics, and the impact on the environment is one of the most important and controversial issues in environmental science.

11. 6-1 How Many People Can the Earth Support?
Concept 6-1 We do not know how long we can continue increasing the earth’s carrying capacity for humans without seriously degrading the life-support system for humans and many other species.

12. Human Population Growth Continues but It Is Unevenly Distributed
Reasons for human population increase:
Movement into new habitats and climate zones
Early and modern agriculture methods
Feed more people per unit of land
Control of infectious diseases through
Sanitation systems
Antibiotics
Vaccines

13. Human Population Growth Continues but It Is Unevenly Distributed
We do not know how long we can continue increasing the earth’s carrying capacity.
There will likely be between billion people on earth by 2050.
97% of growth is in developing countries with many people living in acute poverty.
What is the optimum sustainable population of the earth based on the cultural carrying capacity?
Maximum pop. our planet could support in a sustainable manner that would also allow most people to live in reasonable comfort.

14. Human Population Growth Continues but It Is Unevenly Distributed
U.N. world population projection based on women having an average of 2.5 (high), 2.0 (medium), or 1.5 (low) children.
In 2006, the population of developed countries grew at 0.1% per year.
Developing countries grew 15 times faster at 1.5% per year.

15. Science Focus: How Long Can the Human Population Keep Growing?
Thomas Robert Malthus (1798)
He predicted that the human population would grow exponentially while food production would increase linearly
Human population growth would outstrip the Earth's carrying capacity and that disease and famines would limit humanity's growth.
Although humans have altered 83% of the earth’s land surface, his predictions have not yet come true.
Technology has allowed food production to increase exponentially as well…
...for now.

16. 6-2 What Factors Influence the Size of the Human Population?
Concept 6-2A Population size increases because of births and immigration and decreases through deaths and emigration.
Concept 6-2B The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.

17. Populations Can Grow, Shrink, or Remain Stable
Populations increase through:
Births
Immigration = arrival of individuals from outside the population
Populations decrease through:
Deaths
Emigration = departure of individuals from the population

18. The Human Population Can Grow, Decline, or Remain Fairly Stable
Instead of using raw numbers, crude birth rates and crude death rates are used .
Based on total number of births or deaths per 1,000 people in a population
It makes it possible to compare birth/death rates for countries with greatly different total populations.
It’s also much easier to find population growth rates using the crude birth/death rates than using the raw numbers 18

19. Crude birth/death rates Population comparison
Global Connections:
Crude birth/death rates
Population comparison

20. Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population
The average number of children that a woman bears has dropped sharply.
However, this decline is not enough to stabilize the world’s population in the near future.
Replacement-level fertility: the number of children a couple must bear to replace themselves.
2.1 in developed, 2.54 in developing
Why difference between developed/developing?
Total fertility rate (TFR): the average number of children a woman has during her reproductive years.
2.7 worldwide (1.6 in developed, 2.9 in developing) 20

21. Case Study: The U.S. Population Is Growing Rapidly
U.S. pop. grew by nearly 2.9 million people in 2008:
66% occurred because of births outnumbering deaths.
~34% came from illegal and legal immigration.
In 2008, the TFR in the United States was 2.1 per woman 21

22. Case Study: The U.S. Population Is Growing Rapidly
The population of the U.S. has grown from 76 million in 1900 to 310 in 2010 despite oscillations in TFR and birth rates.
During the Baby Boom ( ) TFR reached 3.7 children per woman.
The baby bust of the 1970’s that followed the baby boom of the 50’s and 60’s was largely due to delayed marriage, more women entering the workforce, contraception, and abortion. 22

23. Case Study: The U.S. Population Is Growing Rapidly

24. Several Factors Affect Birth Rates and Fertility Rates
The number of children women have is affected by:
Importance of children as part of labor force
The cost of raising and educating them
Urbanization
Education and employment opportunities for women
Infant deaths
Marriage age
Availability of contraception and abortion
Religious beliefs, traditions, cultural norms

25. Several Factors Affect Death Rates
The rapid growth of the world's population has not been because of increasing birth rates.
It is because of a rapid decrease in death rates.
Life expectancy – the number of years a newborn infant can expect to live.
Death rates have declined because of:
Increased food supplies, better nutrition
Advances in medicine
Improved sanitation and personal hygiene
Safer water supplies

26. Several Factors Affect Death Rates
Infant mortality rate the number of infants out of every 1,000 who die before their first birthday.
U.S. infant mortality is higher than it should be (ranked 46th world-wide) due to:
Inadequate pre- and post-natal care for poor
Drug addiction
High teenage birth rate
This rate has dropped by almost half from

27. Migration Affects an Area’s Population Size Case Study: The United States: A Nation of Immigrants
Since 1820, the U.S. has admitted almost twice as many immigrants and refugees as all other countries combined.
Most migrants seek jobs and economic improvements.
Others come to escape religious, ethnic, or political oppression.
Environmental refugees – people driven out of an area as a result of environmental degradation.
Water shortage, pollution, rise in ocean level, etc.

28. 6-3 How Does a Population’s Age Structure Affect Its Growth or Decline?
Concept 6-3 The numbers of males and females in young, middle, and older age groups determine how fast a population grows or declines.

29. 6-3 How Does a Population’s Age Structure Affect Its Growth or Decline?
The number of people in young, middle, and older age groups determines how fast populations grow or decline.
Age structure categories:
Pre Reproductive, Reproductive, Post Reproductive
The number of people younger than age 15 is the major factor determining a country’s population growth – they are future reproducers.
Changes in the distribution of a country’s age groups have long-lasting economic, social, and environmental impacts.

30. Populations Can Grow, Shrink, or Remain Stable
The proportion of individuals at various ages is the population’s age structure.
Pre-reproductive age: not mature enough to reproduce.
Reproductive age: those capable of reproduction.
Post-reproductive age: those too old to reproduce.
How fast a population grows or declines depends on its age structure:
Young populations can grow fast
Old populations decrease over time
Even age distribution will result in constant population size

31. Generalized Population Age Structure Diagrams
Populations with a large proportion of its people in the pre-reproductive ages of 1-14 yrs have a large potential for rapid population growth.

32. A Reminder From Chapter 1: Developed vs. Developing Countries
The United Nations classifies the world’s countries into as developed or developing based one their level of industrialization and their per capita GDP.

33. Population Structure by Age and Sex in Developing and Developed Countries
Nearly 28% of the world’s population (1.9 billion) were under 15 years old in 2008.
Includes 30% of the people in developing countries versus only 17% in developed countries.

34. Tracking the Baby-Boom Generation in the United States
Today, baby boomers make up nearly half of all adult Americans and dominate the populations demand for goods and services.

35. Populations Made Up of Mostly Older People Can Decline Rapidly
About 14% of the world’s population live in countries with stabilizing or declining populations.
Japan, Russia, Germany, Italy, Spain, Hungary, Poland, Greece, Ukraine, Czech Republic
Slow decline is manageable
Rapid population decline can lead to long-lasting economic and social problems.

36. Populations Made Up of Mostly Older People Can Decline Rapidly
Rapid population decline can put severe strains on a country’s budget since older people consume a larger share of medical care, social security funds, and other public services that are paid for by a decreasing number of taxpayers.

37. Populations Can Decline from a Rising Death Rate: The AIDS Tragedy
Death from AIDS can disrupt a country’s social and economic structure by removing significant numbers of young adults.
25 million killed by 2008
Sharp drop in life expectancy
Many young adults die:
loss of most productive workers
International community called upon to:
Reduce the spread of HIV through education and health care
Financial assistance and volunteers