Transcript The Human Population

APES Ch. 7
The Human Population
China’s Population &
Environmental Impacts
• 1.3 billion people; 20 % of the worlds
poputation
• Rapid economic development = world’s
largest economy
• “One Child” policy since 1970’s
• Use many tools to meet population
targets such as abortion, sterilizations,
and designation of illegal pregnancies.
• Fertility rate of 1.6 births per woman
China’s Population
• Even if growth stops today, resource
consumption would continue to increase
• Population increased by 30 % between
1985 & 2002, but vehicles inceased by
500%
• Causing pollutants such as CO and
photochemical smog to also increase
• 16 of the 20 most polluted cities in the
world are in China
Earth’s Carrying Capacity
• Up until a few hundred years ago, the human
population was stable (births = deaths).
• Limiting factors determine carrying capacity (scarcity
of resources, diseases)
• Disagreement:
• Will outgrow resources (Malthus, 1798) OR that increase
intellect will provide increase supply of resources.
Factors that Drive Population Growth
• Demography – the study of human populations and
population trends.
Changes in Population Size
Total births have slightly outnumbered deaths =
slow population growth.
Inputs:
• Births & immigration (increase in population)
• Deaths & emigration (decrease in population)
Crude birth rate (CBR) = number of births/1,000
individuals/year
Crude death rate (CDR) = number of
deaths/1,000 individuals /year
• In 2009, there were 20 births & 8 deaths/1,000
Changes in Population Size
Thus you can calculate the Global population growth rate:
[ CBR – CDR]
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For 2009:
[20 – 8] = 1.2%
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Changes in Population Size
To calculate the growth rate for a nation,
immigration & emigration must be
accounted for.
Nat. Pop. = [(CBR + immigr) – (CDR + emigr)]
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Doubling Time = approx. time it takes for
a population to double. Assume constant
growth rate.
Doubling Time
Calculated using the “rule of 70”.
Doubling Time =
70
growth rate
Earth’s population has doubled several
times since 1600 but it is certain it will not
double again.
• In 2050, pop. will be between 8.1 – 9.6 billion
& will stabilize between 6.8 – 10.5 billion in
2100.
Fertility
• Total Fertility Rate (TFR) = an estimate of the
average number of children that each woman
in the population will bear.
• In 2008, TFR for US was 2.1
• Japan, TFR is 1.2
• Kenya, TFR is 4.7
• Fertility helps demographers understand the
role of births in a population.
Replacement-level Fertility
• Replacement-level fertility = the TFR required to
offset the average number of deaths in a
population (stable).
• Usually 2.1 in developed countries
• Depends on prereproductive mortality, which depends
on a countries economic status
• Developing countries (income < $3/person/day) the
replacement-level fertility is > 2.1
US Fertility Rate Over Time
Factors that Affect Birth Rates and Fertility
Rates
• Importance of Children as a part of the labor force
• Urbanization
• Cost of raising and educating children
• Educational and employment opportunities for
women
• Infant mortality rate
• Average age at marriage
• Availability of private and public pension systems
• Availability of legal abortions
• Availability of reliable birth control methods
• Religious beliefs, traditions, and cultural norms
Life Expectancy & Infant Mortality
Rates
• Factors that affect life expectancy &
Infant Mortality Rates are:
• Availability of health care
• Access to good nutrition
• Exposure to pollutants
Life Expectancy
• The average number of years that an infant born
in a particular year in a particular country can be
expected to live.
• Higher in countries with better health care
• High life expectancy also tends to be good
predictor of high resource consumption rates &
environmental impacts
• Reported three different ways (2008):
• For overall population of a country (78 in US)
• For females only (81 in US)
• For males only (75 in US)
Life Expectancy
Good News/ Bad News About Life
Expectancy
• Good news: Life expectancy at birth
has increased globally from 48-67
years
• Developed to 76 years; Developing to 65 years
• Bad news: in the world’ s 49 poorest
countries, mostly in Africa, the life
expectancy is 55 or less. And declining
due to HIV/AIDS.
Infant & Child Mortality
• Infant Mortality – rate of the number of
deaths of children under 1 year of age per
1,000 live births.
• Global = 46 deaths/1,000 live births
• US = 6.6 deaths/1,000 live births
• Sweden = 2.5 deaths/1,000 live births
• Child Mortality – rate of the number of
deaths in children under 5 years of age per
1,000 live births.
Infant Mortality and the U.S.
• Between 1900 and 2002 the U.S. infant mortality
dropped from 165 to 6.8. This led directly to the
increase in life expectancy.
• However even though it is so low the U.S. has 37
other countries with lower Infant Mortality rates
• Why is the U.S. rate so high in comparison?
• Inadequate health care (mainly for poor women)
• Drug addictions among pregnant women
• High teenage birth rates
Aging & Disease
• Disease is an important regulator in human
population
• WHO sated that infectious diseases is the 2nd
largest killer after heart disease.
• Today HIV/AIDS is responsible for the most
deaths by disease
• 1990 – 2007, AIDS related illnesses killed 22
million
Age Structure
• Used to help predict how rapidly a population
will increase and what size it will be in the
future.
• Age structure describes how a populations
members are distributed across age ranges.
• Age Structure Diagrams visually represent the age
structure within a country for males & females
• Each horizontal bar represents a 5-year age group
• The total area of all the bars represents the size of
the whole population.
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A Column-shaped
country with
a greater
amount
of older
Population
pyramid
or square-shaped
– more
young
than
diagram
old
people
thanslow
younger
shows
an inverted
population;
indicates
typical
population
for
developing
growth;
US,
countries;
Sweden,
pyramid.
These
populations
are declining;
like Venezuela
France
are
examples;
& Indiastable
Singapore, Germany, Russia
• Graphed as a population pyramid.
• More young people in a population usually
means higher growth rates.
• The proportion of the population of each sex
at each age level.
• Three age levels:
• Pre-reproductive: 0-14
• Reproductive: 15-44
• Post-reproductive: 45-85+
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Age Structure