Transcript Human Population

Human Population
SOME ALARMING STATISTICS
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Late 1600’s – ½ billion people
1830 – 1 billion
1930 – 2 billion
Since 1975 – world’s population has added 1
billion ever 12 years
• Greatest growth occurring in developing
countries
• By 2050 – 10.5 billion
Causes of “explosion”
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Technology
Improved sanitation
Better medical care
Increased agricultural output
These and others led to a decrease in death
rates, primarily infant death rates
Environmental Impacts
• Cornucopian view – resource depletion is not
a problem if new resources can be found to
replace
• Not all resources are replaceable
• Even if it could, could we maintain the quality
of life we desire?
Environmental Impacts
• IPAT Model represents how human impact (I)
results from interaction among three factors:
• Three factors: population, affluence,
technology
I=PxAxT
• Impact can be boiled down to pollution
and/or resource depletion
DEMOGRAPHY
Demography
• The science of human population
• Principles of population ecology apply to
humans
• Humans have a carrying capacity set by
environmental limitations
• Estimates: 1-2 billion living prosperously to 33
billion living in poverty
Demography
• Uneven distribution means certain areas bear
more burden
• Areas of low population density are often
vulnerable to impact (sensitive environment
that cannot support many people)
• Age structure diagrams show relative sizes of
each age group in a population; used to
predict future population dynamics
Demography
• Population growth depends on rates of birth,
death, immigration, and emigration
= (birth + immigration) – (death + emigration)
• Immigration and emigration play a large role
today
• Since 1970 growth rates in many countries
have been declining
Demography
• Total Fertility Rate (TFR): average number of
children born per female during her lifetime
• Replacement fertility is the TFR that keeps the
size of a population stable; for humans it is 2.1
• A lower infant mortality rate has reduced
people’s tendency to conceive many children
to ensure some survive
• Natural rate of population change is change
due to birth and death rates alone
Demography
• Many nations experience a change called
demographic transition
• This is a model of economic and cultural
change that explains the trends in declining
birth and death rates as nations industrialize
• Four stages: pre-industrial, transitional,
industrial, post-industrial
Demography
• Despite technological advances, earth does
not have enough resources for existing and
future generations to maintain standard of
living equal to developed countries
• Is the demographic transition universal?
POPULATION AND
SOCIETY
Civil Rights for Women
• In societies in which women are freer to make
reproductive decisions, fertility rates have
declined
• Children are better cared for, healthier, and
better educated
Population Policies
• Thailand – relied on education-based approach
to family planning
• India – 1st country to implement population
control measures. Strident policies in the
1970’s. Now focus on education, family
planning
• Brazil, Mexico, Iran, Cuba et al, have instituted
programs with reduction targets, incentives,
education, contraception and reproductive
health care
Population Policies
• UN in 1994 – Cairo conference on population
& development. 179 nations endorsed all
gov’ts to offer repro health care w/in 20 years
• US has often declined to fund family-planning
efforts by the UN
Other Factors & Influences
• Poverty is strongly correlated with pop growth
• Consumption from affluence creates huge
impact on environment
• 1999 – the richest 20% of people used 86% of
world’s resources
• HIV/AIDS leads to premature deaths, reducing
life expectancy in African nations
• AIDS is undermining ability of developing
countries to make transition modern tech