1. 3.1 Human population growth

2. The Population Explosion – Exponential Growth

3. The Population Clock
Population Clock
The global population reached 6 billion in fall of 1999
In 2013 Global Population Topped 7 billion!

5. Limiting factors of population Growth
Availability of food and water
Invasion of parasites, pathogens, or disease
Over-crowding
Sudden Climate changes
Pollution of air, soil and water
If we do not take steps to control population it is likely one of these factors will forcibly reduce our population for us!!

6. Humans Avoid Limiting Factors by…
Importing resources
Improving sanitation and medicine
Expanding habitat
Increasing capacity in existing habitats
Increasing in agricultural technology

7. Key Terms Population: number of persons
Population change: a change (increase or decrease) in the number of persons (per year)
Growth rates: rate of change (per year) includes births, deaths and immigration, and emigration

8. Crude Birth Rate
Crude Birth Rate (CBR)= number of births per population
Example: US Births = 3,999,386 and the total population is 307,645,076 people
(Births / Total Population) x 1000

9. Crude Death Rate
Crude Death Rate (CDR)= number of deaths per population
Example: US Deaths = 2,468,435 and the total population is 307,645,076 people
(Deaths/ Total Population) x 1000

10. Natural Increase Rate (NIR) Rate of Natural Increase (RNI)
Rate Natural Increase is % growth rate based only on birth and death
(Totally ignores immigration and emigration)
RNI = (crude birth rate – crude death rate)
Example: The CBR of USA is 13.0 and the CDR is Calculate the RNI of USA

11. Fertility
General Fertility-(# live births / female reproductive population (15-44) x 1000
Example: US Births = 3,999,386 and female population ages is 62,071,000

12. Fertility Continued
Replacement Fertility: Number of children adults need to have to replace themselves
MEDC ~ 2.1
LEDC ~ 2.3 +
TFR (total fertility rate) =
number of children born to a woman during her reproductive years (or life time)
USA TFR is 2.06
Mali TFR is 7.38 !

13. Total Fertility Rate

14. Infant Mortality Rate IMR (infant mortality rate) =
infant deaths per 1000 live births (infant < 1 yr)
Used as overall indicator of health

15. Infant Mortality rate

16. Doubling Time Number of years in which a population doubles its size
Doubling time can be approximated using growth rates and the rule of 70
Doubling time (T) = ___70_____
% growth rate
Calculate Doubling Time Below
rate: 1.4% doubling time = 50 years
rate: 2.0% doubling time = ______ years
rate: 0.5% doubling time= _______ years
rate: -0.5% doubling time = _______years

17. Growth Rate Human Population Growth Per Year = 1.4%
LEDC (least economically developed country)=1.7%
MEDC (more economically developed country) = 1.0%

18. Rate of Population Increase

19. Factors affecting fertility Rates
Urbanization
Importance of children in workforce
Cost of raising a child
Education/Employment for women
Average age of marriage
Availability of abortion
Availability of birth control
Religious beliefs, traditions and
culture

20. Determining Future populations
Use Ne(rt) formula
N= Current population
e= constant …
r = growth rate as a decimal!!! (Divide by 100!)
t = time in years
Example: 2010 data reports that a population of 2,350,000 has a growth rate of 1.2%. What will the population be in 2025?

21. Carrying Capacity
The maximum population that can be sustainably supported without running out of resources.

22. Population Pyramids

23. Characteristics of MEDC/LEDC
MEDC’s
LEDC’s
industrialized
little or no industry
high GDP (gross domestic product)
low GDP
relatively rich population
provide raw materials but few processed or manufactured goods
access to education and health care
limited access to education and health care
high resource use per capita
fewer resources consumed per person
low population growth rates
most have high population growth rates

24. What is a Population Pyramid?
Graphic device: bar graph
Shows the age and gender composition of a region
Horizontal axis: gender
male: left-hand female: right-hand
absolute number of people or %
Vertical axis: age
5-year or 10-year age groups
Three age population categories
Pre Reproductive- (0-14)
Reproductive- (15-44)
Post Reproductive- (45 +)

26. Why a population Pyramid?
Helps to determine specifics of potential future populations
Shape of pyramid indicates future growth
Can point to future changes in social conditions of a country

27. Population Pyramids

28. Demographic Transition Model

29. Stages of Demographic Transition Model
Pre-industrial
(Stage 1)
LEDC
(Stage 2)
Wealthier LEDC
(Stage 3)
MEDC (Stage 4)
MEDC
(Stage 5)
Birth rate
High
Declining
Low
Very low
Death rate
Moderate
Life expect
Short
Medium
Long
Pop’l growth
Slow
Rapid
Slowing
Stable
Shrinking

30. Reason for changes in the DTM
Birth rates, death rates and growth rates systematically change through time as societies change:
Modernize, urbanize
Gain access to new technology
Births, deaths, migration
Fertility rates play huge role

31. Stage 1 High birth rates, high death rates, low growth rates
Stage for much of human history, traditional societies
Practically no country today

32. Stage 2 High birth rates, declining death rates, rising growth rates
Improvements in sanitation (water) and medicine
Europe during Industrial Revolution
LEDC countries since the 1950’s
Much of Africa today, some countries of Asia (Afghanistan, Nepal)

33. Stage 3
Continued decline of death rates, declining birth rates, growth rates decline from high to lower levels
Change in behavior: adaptation to lower death rate, in particular infant mortality rate
Economic change: urbanization (incentive to have fewer children)
Mexico today

34. Stage 4 & 5
Stage 4: low birth rates, low death rates, low growth rates
United States today
Stage 5: low birth rates, rising death rates, declining growth rates (if birth rates drop below death rates: negative growth rates)
Western Europe, Japan

35. Population Pyramid and Demographic Transition
Stage 2: wide base

36. Population Pyramid and Demographic Transition
stage 3: wide middle

37. Population Pyramid and Demographic Transition
stage 4: slender

38. Population Pyramid and Demographic Transition
stage 5: narrow base

39. Demographic Transitions in China

42. China Population Pyramid 2005

45. Models for Predicting Population growth
Computer simulations:
Can be highly accurate with many variables
Cant include unforeseen events (i.e. natural disaster, terrorist strike, warfare)?
Statistical and/or demographic tables
Include actual field measurements based on past trends.
Past trends may not always predict future trends.
How large/representative are the sample populations?
Age/sex pyramids (
see above)
Population curves
Mathematical extrapolation from graphs based on real data
Less complex than computer models