1. The Human Population
Think of the earth as a living organism that is being attacked by billions of bacteria whose numbers double every forty years. Either the …bacteria dies, or both die. 
- Gore Vidal

2. The Science of Overpopulation…

3. Human Population Growth

4. Early Human History
During the earliest parts of human history, our population survived as hunter-gatherers.
Population during this time was low due to density-dependent growth limiting factors:
Competition for food
Availability of water
Predators
Disease
The indigeonous Hadza people of Tanzania.

5. At some point, estimated to be about 130,000 years ago, Homo sapiens migrated out of Africa into the Fertile Crescent.

6. The Fertile Crescent was an especially biodiverse area, due to several factors:
The area was a geographic “bridge” between two other continents.
Proximity to the Mediterranean sea reduced the impacts of climate change during the ice age.
Variety of elevation created many microclimates.
It included floodplain areas, which receive nutrients from the river.

7. Plowing was used to loosen up the soil.
The Fertile Crescent is seen as the birthplace of agriculture, the growing of plants and animals for food, fiber, and other products.
Plowing was used to loosen up the soil.
Artificial selection was used to breed native animals and plants with desired traits into crops we still use today:
Wheat, barley, flax, chick peas, peas, lentils.
Cows, goats, sheep, and pigs.

8. Agriculture helped reduce the impact of food availability and competition as a density- dependent growth limiting factor, and the human population began to increase.
Other factors, such as disease, were still present.

9. The Industrial Revolution
The Industrial Revolution was a transition from hand production methods to machines, including the increased use of steam power and factories.
During this time, many important medical discoveries were made:
The Germ Theory, the idea that microscopic bacteria and viruses cause disease.
Vaccines, injections of dead or weakened viruses that prevent disease.
Antibiotics, chemical compounds that kill bacteria.
Water treatment, the filtration and addition of chlorine to water to remove microorganisms and toxins.

10. World Population “Dots” Video. Population Connection, 2003.

11. Prior to the industrial revolution, human population growth was fixed, meaning it grew at a consistent rate.
About 0.1% per year.

12. Following the industrial revolution, human population growth was exponential, an increasingly rapid rate with a continuously growing base.

13. Exponential Growth
Exponential growth occurs when the population size and its rate of growth both increase.
It took over 70,000 years to reach 1 billion.
150 years to reach 3 billion.
25 years to reach 4 billion.
20 years to reach 5 billion
12 years to reach 6 billion.
11 years to reach 7 billion.

14. Doubling time is calculated with this equation:
Doubling time is an estimate of how long it will take the population to double in size at its current rate of growth.
Doubling time is calculated with this equation:
70 / (Current % Growth Rate)
Year
Growth Rate
Doubling Time
1543
0.10%
1737
0.12%
1803
0.28%
1928
0.56%
1975
0.92%
1987
1.89%
700 years
583 years
250 years
125 years
76 years
37 years

15. HUMAN DEMOGRAPHY
The rate of population growth varies widely from country-to- country.
Developing countries have populations that tend to be poorer, younger, and are growing much more rapidly.
Developed countries are wealthier, older, and have populations that are stable in size or shrinking.
Developing countries account for most of the human population growth.

16. Demographics is the statistical study of human population data.
Life expectancy measures how long an average newborn will live in a given country.

17. Life expectancy is influenced by the rate of diseases, availability of food and water, conflict, but most of all by infant mortality.
Infant mortality is the number of deaths of infants under one year of age per 1,000 live births.

18. To reiterate…
Life expectancy - the average # of years an infant can expect to live
Infant mortality rate:
The infant mortality rate (IMR) is the number of deaths of infants under one year old, per 1,000 live births.
High infant mortality rate indicates:
Inadequate health care for poor women during pregnancy and their infants (poverty)
Drug addiction among pregnant women
High birth rate among teenagers

19. Several Factors Affect Death Rates (cont’d.)
Less-developed countries
(deaths per 1,000 live births)
Infant mortality rate
World
Figure 6-10: Infant mortality rates for the world’s more-developed countries and less-developed countries, 1950–2012, with projections to 2050 based on medium population projections.
More-developed countries
Year
Fig. 6-10, p. 129

20. The total fertility rate, the average number of children a woman will have in her lifetime.
A total fertility rate of 2.1 is considered replacement level and will result in a stable population.

21. Gross domestic product (GDP) is the total value of goods produced and services provided in a country during one year.
GDP per capita divides the GDP by the total population.

22. The Genuine Progress Indicator is a metric designed to incorporate factors ignored by GDP.
Income inequality
Costs of environmental degradation
Social factors, such as education, leisure time, family dynamics

23. The use of GPI reveals social and environmental issues hidden by GDP.

24. Migration
The movement of individuals between areas can have a major impact on population change.
Emigration is when people move out of an area.
More likely to occur in developing countries.
Immigration is when people move into an area.
More likely to occur in developed countries.
Ellis Island

25. For a developed country, immigration can mean the difference between low, positive growth rates, and negative growth.

26. Calculating Population Change
(births + immigration) – (deaths + emigration)
Crude birth rate
The number of live births/1000/year
Crude death rate
The number of deaths/1000/year

27. NATURAL CAPITAL DEGRADATION
Altering Nature to Meet Our Needs
Reduction of biodiversity
Increasing use of the earth's net primary productivity
Increasing genetic resistance of pest species and disease-causing bacteria
Elimination of many natural predators
Introduction of potentially harmful species into communities
Figure 6.A
Major ways in which humans have altered the rest of nature to meet our growing population’s resource needs and wants. See an animation based on this figure at CengageNOW. Questions: Which three of these items do you believe have been the most harmful? Explain. How does your lifestyle contribute directly or indirectly to each of these three items?
Using some renewable resources faster than they can be replenished
Interfering with the earth's chemical cycling and energy flow processes
Relying mostly on polluting and climate-changing fossil fuels
Fig. 6-A, p. 124

28. Population Pyramids
Population pyramids graphically show the distribution of defined age groups, separated by gender.

29. Countries in rapid growth will be pyramid-shaped, with a wide base of young people.
Countries in slow growth have age groups that are roughly equal.
Countries in negative growth have narrower bases, indicating a fertility rate below replacement level.

30. Demographic Transition
The fertility rate and population growth patterns in a given country will not remain constant. They change based on a wide variety of factors.
United States Fertility Rates,

31. Demographic Transition Model
The demographic transition model is a series of stages countries generally pass through as they industrialize and transition from developing to developed countries.
Each stage is marked by changes in birth rate, death rate, living conditions, and cultural norms.

32. No present-day country is in the pre-industrial age.
During the pre-industrial stage, food shortages, malnutrition, poor sanitation, and lack of access to modern medicine keep death rates high.
High birth rates counteract this, resulting in stable population sizes.
No present-day country is in the pre-industrial age.

33. Preindustrial cultures had significant pronatalist pressures to ensure high birth rates.
Pronatalist pressures are policies or cultural beliefs aimed at increasing the birth rate or maintaining a high birth rate, which was needed for:
A source of support for elderly parents.
Aid in supporting family income.
Counteracting high child mortality rates.
The son preference: a desire to have a male child.

34. Populations in early transition countries grow exponentially.
During the early transition stage, access to food and medicine improve, leading to a rapid drop in death rates.
Birth rates remain high, as pronatalist cultural norms and pressures remain in place.
Populations in early transition countries grow exponentially.

35. The population continues to increase, but at slower and slower rates.
During the late transition stage, death rates remain low, and efforts are made to reduce birth rate.
Birth control and sex education gain greater acceptance.
Women play a greater role in family planning.
Educational and professional opportunities for women increase.
The population continues to increase, but at slower and slower rates.

36. The industrial stage marks the point where birth rates have fallen back into balance with death rates.
Total fertility rate is close to replacement level (2.1 children per couple), causing the population to stabilize.

37. The population size decreases.
During the post-industrial stage, birth rates continue to fall due to antinatalist pressures
Total fertility rate is below replacement level.
The population size decreases.

38. The length of time a country spends in the early and late transition stages determine how large its population will be when it is fully industrialized.

39. Four Stages of the Demographic Transition

40. Some countries have instituted antinatalist programs and laws to rapidly reduce birth rates and accelerate the demographic transition.
China implemented a one child policy in that was altered to a two-child policy in

41. Antinatalist efforts, combined with a son preference, have left some countries with a disproportionate number of boys compared to girls.

42. Some Problems with Rapid Population Decline
Can threaten economic growth
Labor shortages
Less government revenues with fewer workers
Less entrepreneurship and new business formation
Less likelihood for new technology development
Figure 6.11
Some problems with rapid population decline. Question: Which three of these problems do you think are the most important?
Increasing public deficits to fund higher pension and health-care costs
Pensions may be cut and retirement age increased
Fig. 6-11, p. 133

43. FUTURE OF HUMAN POPULATIONS
Most demographers believe the world population will stabilize sometime during the next century.
Population projections vary depending on how quickly developing countries pass through the demographic transition.

44. 5 Human Impacts on the Env