1. The human population and the environment Chapter 7
AP Environmental
The human population and the environment
Chapter 7

2. History of Human Population Growth
The human population increased slowly until the last 200 years
Initially the human population was limited by resources provided by the land and higher mortality rates for a younger age demographic

3. History of Human Population Growth
Hunters and gatherers
The world’s population was probably less than a few million
Early, pre-industrial agriculture
Allowed a much greater density of people
The first major increase in human population
Machine age
Industrial revolution led to rapid increase in human population
The Modern era
Rate of population has slowed in wealthy nations but continues to increase rapidly in poorer, less developed nations.

4. Current Human Population Growth
Technology, medical advancements, better sanitation and food distribution have all contributed to the current exponential growth of the human population
Estimates state that every second 4 children are born and one person dies
Overpopulation trends have been identified as the biggest contributing factor in resource depletion and environmental degradation

5. Population Changes
Exponential growth represents a constant net rate of increase.
The rate of net increase for the human population in the graph has exceeded the exponential rate
Factors like a decline in death rate have caused the growth in the net rate of increase

6. Exponential growth and doubling time
The current growth rate for the human population falls between 1-2% so doubling time is expected to be between years.
*Remember: doubling time = 70/R
No population can sustain exponential growth rate indefinitely because of resource constraints within the environment so some scientists believe that the human population will start to level out around 11 billion people by year 2100

7. How do we measure the human population?
A group of individuals of the same species living in the same area of interbreeding and sharing genetic information.
Species:
All individuals that are capable of interbreeding.
Made up of populations
Population dynamics
The general study of population changes.

8. Population Dynamics Formula to represent population change:
Human population is usually presented as a crude rate which is a given number per 1000.
Example: If the crude death rate is 9 then that represents 9 out of every 1000 people died in that given time frame. Expressed as a percentage this would equal 0.9%.
Crude growth = crude birth rate – crude death rate ( g = b-d) and represents a net change in the population
P1 = number of individuals at a given time
P2 = number of individuals at a later time
P2 = P1 + (B – D) + (I – E)

9. Population Dynamics
Growth rates can be determined using a series of equations that factor in the number of births or deaths in a population with a known population size (N).
birth rate (b)= B/N
death rate (d) = D/N
Growth rate (g) = (B-D)/N

10. Perspectives on Population Growth
Given the current population of the Earth, what factors influence population growth rates in the future and how the size of the human population will impact the environment?

11. Perspectives on Population Growth
Thomas Malthus (1798 An Essay on the Principle of Population)
Argues that population growth is tied to food resources so when the population gets too large the lack of food resources will cause the population to decline
Depletion of resources will lead to poverty, war, starvation, etc.

12. Perspectives on Population Growth
Karl Marx ( )
Argued that poor economic and social conditions (oppression of workers, exploitation of resources) led to poverty which in turn led to higher birth rates and more resource depletion
With increasing environmental degradation and resource depletion overpopulation would lead to unequal distribution of resources, starvation, war, etc.

13. Perspectives on Population Growth
The opposing viewpoints of Malthus and Marx beg the question:
Is it more important to focus on reducing population size or reducing poverty to prevent further environmental degradation?

14. China Case Study
1960’s : uncontrolled population growth was leading to food resource issues and the possibility of mass starvation in some provinces
1970’s: government begins to focus on slowing population growth
1979: Implementation of “One Child Policy”
Encouraged young professionals to focus on career before family
Government offered free contraceptives, sterilization and abortion
Families that agreed to one child given increased pension, better housing, free food, salary bonuses, free medical care and free school (all taken away if families later exceeded one child)
2001: Studies showed fertility rates dropped from 6.5 to 1.3 children per woman
2015: Phase out of “One Child Policy”

15. Population Solutions Delay the age of first childbearing by women
Birth control
Biological and Social
Breast-feeding, which can delay resumption of ovulation
Abstinence
Induction of sterility with natural agents
Contraceptive devices
National Programs to Reduce Birth Rates
Formal family planning programs to
explain the problems arising from rapid population growth
Describe the benefits to individuals of reduced population growth.
Education
Jobs for women
Family planning flyer from Singapore

16. Where do you see population trends increasing? Why?
Population Changes
Where do you see population trends increasing? Why?

17. Population Changes

18. Growth Factors
Total Fertility Rate (TFR) is a major factor in the growth or maintenance of a population over time.
Total fertility refers to the average number of children that could be born to a woman if she follows the normal rates of fertility and survives from birth through her reproductive years.
An important figure in fertility is called Replacement Level Fertility.
Replacement level fertility means that a woman produces enough children to maintain the current population levels

19. Growth Factors
Fertility rates are generally higher in developing countries because of a need for labor and caregivers within the household, a lack of education in birth control, and cultural beliefs
Worldwide fertility rates are dropping due to higher levels of urbanization, especially in developing countries (Current TFR = 2.6)
If fertility rates were to drop below replacement levels then the population could stabilize by 2100

20. Population Outlook

21. Age Structure Graphs Population age structure:
The proportion of the population in each age class, also divided by gender
Shows possible effects on current and future birth rates, death rates and growth rates
Can be used as a predictor for future impacts on the environment
Can predict complications for current and future social and economic status in a country.

22. Age Structure

23. Population Growth Factors
Mortality rates are dependent upon access to clean water, good hygiene, sanitary living conditions and access to medical care
Declining mortality, not increases in fertility contribute to current population growth
World mortality rates do not currently offset natality rates leading to natural increases in most populations
The current growth rate of the world is 1.08% meaning the population will double in approximately 65 years

24. Population Growth Factors
Life expectancy is the average age a newborn infant is expected to attain
For most of human history average life expectancy was 30 years
Increased medical care, sanitation, etc. have increased the average life expectancy to 71.2
Life Expectancy By Country (2017 data from CIA Factbook)
Top 5
Bottom 5
Monaco
Swaziland
Japan
Gabon
Singapore 85.2
Afghanistan
Macau
Guinea-Bissau 51
Iceland
Chad

25. Population Growth Factors
Life Expectancy Patterns:
Women generally have higher life expectancies than men
Life expectancy tends to increase with annual income
Worldwide life expectancy has been steadily increasing in the last 30 years

26. Demographic Implications
As populations stabilize and reduce the number of children born into a country the ratio of people in the young working class begins to drop below the numbers of those in the older age groups that are retired and are dependent upon government support
Higher numbers of older, non-working individuals puts a stress on the economy of a country
Sudden increases such as the “baby-boomer” population in the United States can also cause temporary stresses

27. Birth Dearth
In developed countries fertility rates have started to drop below the standard fertility rate of 2.1 children per woman needed to maintain a population (Italy 1.5, Japan, 1.3)
Declining populations in these countries will no longer be able to fill the jobs needed to support the economy or provide soldiers to bolster military strength
By 2030 the former world superpower countries in Europe and North America may only account for 9% of the total world population

28. Immigration/Emigration
Movement of people between countries has become necessary for economic stability of countries experiencing fertility declines
The United States averages 800,000 immigrants each year entering the population while European numbers have seen numbers in the millions due to the recent refugee crisis
2016 estimates for number of refugees was 60 million

29. How did we get here?
Much of the current population growth today can be attributed to the economic development that occurred during the industrial revolution
Economic development leads to increased jobs, better medicine and improved living conditions for a population
Modernization of a population affects birth and death rates over time in a demographic transition

30. Demographic Transition
Three-stage pattern of change in birth rates and death rates.
Occurred during the process of industrial and economic development of Western nations.
Leads to a decline in population growth.
Stage I: Decline in death rate
Stage II: High growth rate
Stage III: Birth rate drops toward the death rate, leading to low or zero growth rate

32. Demographic Transition

33. Demographic Transition

34. Demographic Transition
Benefits
Population stabilization
Increased technology availability
Growing prosperity and social reform
Concerns
Countries that get “trapped” in the middle transitional stage
Social justice