3.1 HUMAN
POPULATION GROWTH
THE POPULATION EXPLOSION –
EXPONENTIAL GROWTH
THE POPULATION CLOCK


Population Clock
http://www.census.gov/main/www/popclock.html
The global population reached 6 billion in fall of 1999
REASONS FOR POPULATION EXPLOSION
 Expansion
of habitat
 Increased capacity in existing habitats
 Importing resources
 Improved sanitation and medicine
 Increase in agricultural technology
LIMITING FACTORS OF POPULATION
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!!

POPULATION, POPULATION CHANGE, GROWTH
RATES
Population: number of persons
 Population change: increase in the number of
persons (per year)
 Growth rates: rate of change (per year) includes
births, deaths and immigration, and emigration

MEASURING POPULATION GROWTH
USE: INTERNATIONAL DATA BASE HTTP://WWW.CENSUS.GOV/IPC/WWW/IDBNEW.HTML,
THEN ONLINE DEMOGRAPHIC AGGREGATION

Crude Birth Rate (CBR)= number of births per 1000
population



Today: 21.3
Crude Death Rate (CDR)= number of deaths per 1000
population


1990: 24
1990: 9
Today: 8.93
Rate Natural Increase is % growth rate without
migration
RNI = (crude birth rate – crude death rate)
10


1990: 1.5%
Today: 1.4%
growth rates have come down
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%
rate: 2.0%
rate: 0.5%
rate: -0.5%
doubling time = 50 years
doubling time = ______ years
doubling time= _______ years
doubling time = _______years
GROWTH RATE



Human Population Growth Per Year = 1.4%
LEDC (least economically developed country)=1.7%
MEDC (more economically developed country) = 1.0%
RATE OF POPULATION INCREASE
SPECIAL KINDS OF FERTILITY AND MORTALITY
RATES

TFR (total fertility rate) =
 number
of children born to a woman during her
reproductive years (or life time)
 1990: 3.1
2000: 2.8

IMR (infant mortality rate) =
 infant
deaths per 1000 live births (infant < 1 yr)
 Used as overall indicator of health
 1990: 62
2000: 56
(1900: 200)
TOTAL FERTILITY RATE
INFANT MORTALITY RATE
CALCULATING FUTURE POPULATION

Use Ne(rt) formula
 N=
Current population
 e= constant 2.71828…
 r = growth rate as a decimal!!!
 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?
CARRYING CAPACITY

The maximum population that can be
sustainably supported without running out of
resources.
3.1.3 POPULATION PYRAMIDS
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
POPULATION PYRAMIDS
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 population categories
Pre Reproductive- (0-14)
 Reproductive- (15-44)
 Post Reproductive- (45 +)

EXAMPLE FROM BANGLADESH
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

POPULATION PYRAMIDS
BANGLADESH POPULATION OVER TIME
3.1.4 DEMOGRAPHIC TRANSITION MODEL
STAGES OF DEMOGRAPHIC TRANSITION MODEL
Stage
PreWealthier
LEDC
MEDC
MEDC
industrial
LEDC
(Stage 2)
(Stage 4) (Stage 5)
(Stage 1)
(Stage 3)
Birth
rate
High
High
Declining
Low
Very low
Death
rate
High
Moderate
Low
Low
Low
Life
expect
Short
Medium
Long
Long
Long
Pop’l
growth
Slow
Rapid
Slowing
Stable
Shrinking
FIVE STAGES OF THE DEMOGRAPHIC
TRANSITION

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
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

STAGE 1



High birth rates, high
death rates, low
growth rates
Stage for much of
human history,
traditional societies
Practically no country
today
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)
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
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
COMPARISON OF POPULATION PYRAMIDS
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