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Human population growth
IBESS 3.1
Population growth
• Population size, for any species, is
affected by two inputs and two outputs,
which are influenced by a number of
different factors.
Calculating Population ChangeBirths, deaths, and net migrations
determine the numbers of individuals in a
population
According to the United Nations Population
Fund global population reached 7 billion on
Monday, October 31st, 2011
http://www.worldometers.info/world-population/
India and China make up 37% of the world’s population
How to determine crude birth
rates
• Determined by taking the number of live
births in one year in a country, dividing it
by the country’s population and
multiplying the number by 1000
Birth rates
• The number of births per year divided by the total population.
b = total births/total population
*the crude birth rate is usually stated as the number of births per 1000 individuals.
Birth rates, an example
• If the total population of mice in a forest is 1,000,000 and 5,000 mice were born in a one year time period the birthrate would be
5,000/1,000,000 = 0.005 or 0.5%
• The crude birth rate is what is usually reported which would be
5 out of 1000 Confusing I know!
How to determine crude death
rates
• Determined by taking the number of
deaths in a country in one year, and
dividing it by the country’s population
and multiplying the number by 1000
Death rates
• The number of deaths per year divided by the
total population.
d = total deaths/total population
• The crude death rate is usually stated as the
number of deaths per 1000 individuals
Death rates, an example
• So for the same population of mice in a forest (1,000,000) there were a total of 2,500 deaths…so
2,500/1,000,000 = 0.0025 or 0.25%
• The crude death rate reported would be 2.5 out of 1000 (2.5/1000)
In your notebooks:
• A rabbit population is 2,000,000 and there
were 57,638 births. What is the crude birth
rate?
• In the same population there were 7,888
deaths that year. What is the crude death
rate?
• Is this population rising or decreasing?
In your notebooks:
• A squirrel population is 320,000 and there
were 7,532 births. What is the crude birth
rate?
• In the same population there were 15,867
deaths that year. What is the crude death
rate?
• Is this population rising or decreasing?
LEDC and MEDC
MEDC and LEDC
MEDCMore economically developed country
LEDCLess economically developed country
1. Most countries in Europe and North
America, Israel, and Japan
2. Industrialized nations with high
GDPs
3. Population is relatively rich
4. Individuals are unlikely to starve
through poverty
5. Relatively high level of resource
use per capita (per person)
6. Relatively low pop. Growth rates
largely due to low CBR but rising
CDRs
7. Have very high carbon and
ecological footprint
1. Most countries in sub-Saharan
Africa. Large areas of Asia and
South America
2. Less industrialized or have hardly
any industry at all
3. May have raw materials (natural
capital) but this tends to be
exported and processed in MEDCs
4. Population has a lower GDP and
higher poverty rates
5. More people are poor with low
standards of living
6. High pop. Growth rates largely due
to rapidly falling CDRs
7. Have lower carbon and ecological
footprint
Take notes on this documentary I
will grade this separate from
notebook grade.
• https://www.youtube.com/watch?v=-
UbmG8gtBPM
Demographic transition model
• This model describes the pattern of
decline in mortality and fertility of a
country as a result of economic and
social development.
• It is described as a five-stage population
model.
•
• Demographic transition- broad generalization about
population growth since the middle of the 18th century
• No country as a whole retains the characteristics of stage 1.
This only applies to the most remote societies on Earth.
• All MEDC’s are stage 4 or 5
• The poorest of LEDC’s are in stage 2 (Niger, Bolivia)
• Most LEDC’s with advanced social and economics are in stage
3. (Brazil, China, India)
Stage 1
The high stationary stage
• Pre-industrial society
• High birth rate due to no birth control.
• High infant mortality rates.
• Cultural factors and agricultural society encourage
large families.
• High death rates due to disease, famine, poor
hygiene, and little medicine.
• Fluctuating population growth, overall no growth.
Stage 2
The early expanding stage
• LEDC
• Death rate drops as sanitation and food improve.
• Disease is reduced so lifespan increases.
• High population under the age of 15
• Birth rate is still high so population expands rapidly
and child mortality falls due to improved medicine.
• High growth rate.
Stage 3
The late expanding stage• Wealthier LEDC
• As a country becomes more developed, birth rates
will also fall due to access to contraception,
improved healthcare, education, emancipation of
women.
• Increased mechanization reduces need for
workers.
• Desire for material goods increases.
• Infant death rates decrease.
• Smaller families.
• Growth begins to level off.
Stage 4
The low stationary stage
• MEDC
• Low birth and death rates.
• Industrialized countries.
• Stable population sizes.
• Life expectancy increases
Stage 5
The natural decrease stage
Newly added stage
• MEDC
• Population may not be replaced as fertility
is low.
• Problems of aging workforce put pressure
on economy.
• Birth rate may have fallen below death rate
resulting in natural decrease
Explains 4 stages of
demographic transition
• https://www.youtube.com/watch?v=-
XlLN5E1nIY
Age-structure pyramids
• Age-structure pyramids are a graphic
representation of the age and gender
structure of a population.
• The pyramids are a snapshot in time but
can give a great deal of information
about the demographics of the
population.
How to construct a pyramid
• Calculate the percentage of the population that falls into each age category, and separate by gender.
• Take the number of individuals that fall into the age/sex category, divide by the total population and multiply by 100.
Cut out and color the two sides different. Males blue and females red
• Do pyramid activity packet
Analyze and
interpret the
pyramid
Analyze
• There is a wide base
• Decrease in width as
age increases
Interpret
• extremely high fertility rates.
• indicates relatively high
mortality rates
• The wide base reflects
extremely high fertility
rates.
• Birth rates are 48 per
1000
• Decrease in width
indicates relatively high
mortality rates
• Death rate 12 per 1000
• Infant mortality rate very
high 88 per 1000
• Life expectancy is 55
• 49% of pop. Under the
age of 15
• Stage 2
Analyze Interpret
• Lower fertility rates by
narrow band compared to
the middle age band
• 13 per 1000 births
• Decline in mortality by
each narrowing band
• Greater life expectancy
• Life expectancy is 80
• 9 per 1000 death
• Stage 4
What pyramids say about the population
Expanding pyramids
• This population is very bottom heavy.
• The birth rates are high.
• Most of the population is young, causing competition for jobs and resources.
Still expanding but the birth rate is dropping and growth rate is slowing.
Chimney shapes indicate that birth and
death rates are both low, population
growth is close to zero.
Contracting pyramid indicates a declining growth rate.
This can cause a financial burden on the working age
individuals to support an aging population.
Population Doubling Time
• Doubling Time of a population is the number of years
it would take a population to double its size at its
current growth rate.
• Knowing the doubling times of populations is useful in
making international comparisons or variations within
countries.
• Population doubling makes people consider the
impact of population growth on resources and the
environment in general.
Population Doubling Time
Calculation doubling times
• Doubling time is determined by dividing 70 by the growth
rate.
• The number 70 comes from the natural log of 2, which is 70
• Example:
A country in 2010 with a population of 33 million had a
population growth rate of 0.9%
Population doubling time:
70/0.9 = 77.7 years
So, in 2087 if growth rate maintained, the country will have
doubled it pop. From 33 million to 66 million
Environmental FactorsEnvironmental factors may be
categorized according to how much
population density influences their effect
on population growth:
Density independent factors have a
controlling effect on population size and
growth, regardless of the population
density.
Density dependent factors have an
increasing effect on population growth as
the density of the population increases.
Severe fires can result in high mortality
Humans often live at high density
Density Dependent FactorsDensity dependent factors exert a greater
effect on population growth at higher
population densities.
At high densities, individuals:
Compete more for resources.
Are more easily located by predators and parasites.
Are more vulnerable to infection and disease.
Density dependent factors are biotic factors
such as food supply, disease, parasite
infestation, competition, and predation.
Parasites can spread rapidly
through dense populations
Competition increases
in crowded populations
Density Independent
FactorsThe effect of density independent factors
on a population’s growth is not dependent
on that population’s density:
•Physical (abiotic) factors
•Temperature
•Precipitation
•Humidity
•Acidity
•Salinity
•Catastrophic events
•Floods and tsunamis
•Fire
•Drought
•Earthquakes and Eruptions
When is a country overpopulated?
• The optimum pop. Is when pop. Produces
highest economic return per capita, using all
available resources.
• Some countries have higher optimum pop.
Densities than others
• Netherland has high pop. Densities but can
support this w/ high living standards
• Brazil in the north w/ 2 people for km2 is
overpopulated as resources are much scarcer.
When is a country overpopulated?
• richer countries import goods and services
from elsewhere.
Why do people have large families?
• High infant and childhood mortality rate
• According to UNICEF one child dies every 3
seconds (26,500 per day) due to malnutrition and
disease. It is an insurance to have more than you
may need so that some reach adulthood.
Why do people have large families?
• Security in old age
• The tradition in the family is that children will care
for their parents. The more children the more
secure the parents and less burden for each
child. If no social welfare network, children need
to take care of parents
Why do people have large families?
• Children are economic asset
• Agriculture society they work on the land asap.
More kids can help take care of younger ones.
• In MEDCs children depend on their parents and
take longer to contribute to society.
Why do people have large families?
• Status of women
• Traditional position of women they are
subordinate to men.
• In many countries deprived of many rights:
• Owning property
• Education
• Career
Why do people have large families?
• Status of women
• They do most agricultural work and are
considered worthy only for making children and
their social status depends on the number of
children they produce (especially boys)
Ways to reduce family size
• Provide education
• Basic literacy for children and adults
Ways to reduce family size
• Provide education
• Basic literacy for children and adults
Ways to reduce family size
• Improve health care
• By preventing the spread of diseases through
simple measures of hygiene (boiling water), by
improving nutrition, and providing medicine and
vaccines
Ways to reduce family size
• contraceptives
• Education on family planning and making
contraceptives available
Ways to reduce family size
• Enhance Income
• Small loans given to families to buy seeds or
equipment necessary to start a small family
business.
Ways to reduce family size
• Biggest factor in reducing population….
Improved status of women
Ways to reduce family size
• Improved status of women
• Fertility rates are high where women status is low
• Less than 20% world’s countries will account for
nearly all of the world population growth
• Those countries are least developed and girls are
most likely less to attend school
• Child marriage is common
• Women lack basic rights
Human Population growth and
resources
• More people require more resources
• More people produce more waste
• People usually want to improve their standard
of living
• So the more people there are, the greater the
impact they have
• If we can control pop. Increase and control
resource demand, levels of sustainability should
increase
Population growth and food
shortages
Use 2 pages of your notebooks one side for
Malthusian theory and the other for Boserup’s
theory.
• What are each?
• What are the limitations of each?
• What are the applications of each?
• Include graphs
• Pages 357-359
Carrying Capacity
• The largest number of individuals in a
population that the resources in the
environment can support for an
extended period of time
