l10 human pop
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HUMAN POPULATION
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Nt+1
= Nt+ Births – Deaths + Immigration – Emigration
Populations can be described with simple models
reindeer, marine algae, or humans.…for reindeer, marine algae, or humans, the same rules apply
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• Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Nt+1 = Nt + Births – Deaths
Global population: why were there so few of us?
• Predators,
parasites,pathogens
• Famine &dependence on
found food
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Population distribution is not even, globally
Source: United Nations Population Division, Briefing Packet, 1998 Revision of
World Population Prospects.
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The world's population distribution has notchanged much over time
• In 1800, 86% of the world's population resided in Asia and Europe,65% in Asia alone; currently Asia still represents nearly 60%.
• 1900, Europe's population represented 25% of the world, fueled bythe Industrial Revolution. Some of this spilled over to the Americas.
• After World War II, growth accelerated as less developed countriesbegan to increase dramatically.
• A billion people were added between 1960 and 1975. Another billionwere added between 1975 and 1987.
• Human population entered the 20th century with 1.6 billion peopleand left the century with 6.1 billion.
• 1789, Thomas Malthus studied population growth in Europe. Heobserved that populations grow geometrically (1, 2, 4, 8 …), rather thanarithmetically (1, 2, 3, 4 …), like food production. He feared eventualglobal starvation.
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Population growth rates are not even, either
Why are some countries declining, others stable orincreasing in population?
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Rate of Natural Increase
Rate of Natural Increase: Rate at which a population isincreasing (or decreasing) in a given year due to a surplus(or deficit) of births over deaths.
• 1700s start of
the modern era ofpopulation growth
• 1850-1900:annual globalgrowth ratereached 0.5%.
• mid-1960s:surged to 2.0%;
• mid-1980s:dropped to 1.7% 2000 down to
~1.4%.
Drop inbirthrate, late20th century.
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Crude birth rate - The average annual number of live births during a year per 1,000 population
Crude death rate - The average annual number of deaths during a yearper 1,000 population
Global population isgrowing, but not evenlyaround the world.
In some countries,
death > birth (Belgium,Finland)
In many countries,birth < death (developingcountries, e.g. Cameroon)
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• Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Source: U.S. Census Bureau, Current Population Reports .
Nt+1 = Nt + Births – Deaths + Immigration – Emigration
Percentage of U.S. PopulationGrowth from Migration
• Most Americans, Australians,and Brazilians are immigrants or descendants of immigrants
• 2/3 of United Statespopulation growth is fromnatural increase and 1/3 isfrom immigration andinternational migration.
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Source: Immigration and Naturalization Service, 1998 Statistical Yearbook .
Nt+1 = Nt + Births – Deaths + Immigration – Emigration
Regional Origins of Immigrants to the United States
People move for economic (agriculture, labor), political, and religious reasons.
Current immigration to the U.S. isestimated at ~100-500K per year
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•
Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Ages 0-14 Ages 15-44 Ages 45-85+
Male FemaleMale Female
Rapid GrowthCameroon
Nigeria
Saudi Arabia
Slow GrowthUnited States
China
Canada
Zero GrowthSweden
Austria
Germany
Negative GrowthEstonia
Latvia
Russia
Population Age Structure
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100
10
1
0
Age
Population age structure viewed a different way:
Survival rates vary with age among human populations just as they do among other animal species
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Age
Fem. Males
Age
Females Males
2416
8448
1620
Millions 2416
8448
16
Millions
Age Age
Females Males Females Males
20 168 4
4 8 16 20
Millions 2416
8448
1624
Millions
1955 1985 2015 2035
Age structures can change through time
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•
Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Largest urban agglomerations through time
More developed nations: 76% urban; Less developed nations: 40% urban
2015: 23 cities expected >10 million people; 19 in less developed countries.2030: 60% of the world population is expected to be urban.
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•
Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Women’s age at first reproduction and family size
Source: Demographic and Health Surveys , 1991–1999; and Carl Haub andDiana Cornelius, 2000 World Population Data Sheet (Washington, DC:
Population Reference Bureau, 2000).
strong relationship betweenage at first reproductionand # children.
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Assuming births > deaths, shorter generation times result in fasterpopulation growth
P1 + P2
G1 G2 G3 G4
K2K1
15
15
15
P1 + P2
K2K1
25
25
Descendants by age 65:
630
Nt+1
= Nt
+ Births – Deaths
Women’s age at first reproduction and population growth
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Women’s education and family size
Source: Demographic and Health Surveys , 1991–1999.
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•
Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Life expectancy has increased through time
Source: World Bank, Demographic Trends and Prospects
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Life expectancy remains uneven, globally:a different view
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Infant mortality is a sensitive measure of a nation’s health
Source: World Bank, World Development Indicators 2002 .
Source: UNICEF, The State of the
World's Children, 1998.
Mortality sources under 5 years-1995
Less developed countries
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AIDS is causing decreased life expectancy in many countries
Source: UNAIDS, Report on Global HIV/AIDS Epidemic, 2000
Source: World Bank, World Development Indicators, 2004
Percent of world's HIV/AIDScases, 1999
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•
Population growth and distribution
• Effect of migration on population growth
• Population age structure
• Patterns of world urbanization
• The status of women
• World health
• Human relationships with the environment
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Global impacts of humans,…on humans!
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Replacement reproduction
Replacement reproduction – replacement of a couple with the samenumber of people (an average of one boy and one girl).
It can also be defined as (an average of) one daughter born to eachmother (red line).
A fertility rate of ~ 2.1 or 2.2 children/couple is the replacement rate thatallows a constant population.
Nt+1 = Nt + Births – Deaths
Replacement reproductiondepends on both birth anddeath rates
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