Population Growth

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Population Growth
World population now over ?? billion
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• Population growth
• Limits to growth some opposing views
• Human demography
• Population growth opposing factors
• Demographic transition
• Population (fertility) control
• The future of human populations

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POPULATION DYNAMICS

• Population Growth
• Exponential Growth unrestricted growth. Growth
  as a percentage of the whole.
• dN/dt r N
• Biotic Potential - Potential of a population to
  grow in the absence of expansion limitations.

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Boom and Bust Cycles

• Exponential growth is graphed as a J curve.
• Carrying Capacity - Number of individuals that
  can be indefinitely supported in a given area.
• Overshoot - When a population surpasses the
  carrying capacity of its environment.
• Dieback
• Oscillations

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Population Oscillations
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Population Oscillations
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Abiotic Biotic Controls
Changes in pop No predators lots of
vegetation so moose increase, Vegetation
heavily eaten decreases so moose crash
then increase stabilize, Wolves arrive
and moose decrease, Wolves decrease w less
genetic variation and canine virus
introduced by dogs so moose increase.
Moose decrease due to lack of food, poor
reproduction, severe winter and tick
infestation so crash.
Isle Royal on Lake Superior
Miller 2002
Moose and wolves stabilize
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Growth to a Stable Population

• Logistic Growth - Growth slows as the population
  approaches carrying capacity.

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Limiting Factors

• Environmental Resistance
• Density-Independent Factors - Effect on mortality
  rate is independent of population density.
• Abiotic conditions.
• Density-Dependent Factors - Mortality rates
  increase as the density of the population
  increases.
• Disease, Stress, Predation

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World Population Density
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• Increasing Population
• Cons
• increasing pollution,
• poor human health,
• resource overuse
• etc
• etc??
• Pros ?
• greater chance of
• intelligence ingenuity solving problems,
• ?

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Population Estimations

• World pop
• 2010 6,793,593,686 Jan 1, 2010
• US pop
• 2010 308,435,073 At 10 AM Jan 6, 2010
• In U.S. 2005 2006
  2007 2008 2009
• 1 birth every 8 8 8 8 8
  secs
• 1 death every 13 12 11 11 12 secs
• 1 intnl migrant (net) every 26 31 27 30
  36 secs
• 1 NET person every 12 14 15 13 14
  secs
• http//www.census.gov/main/www/popclock.html
• http//www.ibiblio.org/lunarbin/worldpop
• Births and deaths accounted for in these
  estimations!

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Current Birth and Death Rates of the World

• Every second 4 or 5 children are born, while 2
  other people die
• Net gain 2.3 humans added to the world
  population every second (1.14 per year)
• 74.6 million added every year

(Cunningham Cunningham 2008)
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Effect of Birth Rate and Death Rate on Population
Size
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Human Population Levels Throughout History
Critique graphics used to present concepts!!!
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Growth to a Stable Population
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Population Growth
N Amer
Latin Am Carib
Europe
Asia Oceania
Africa
World Resources 1998-99
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Overshoots and Diebacks
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Basic Causes of Environmental Problems??
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Throughput
Throughput
(McKinney Schoch)
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P x A x T
Environmental Impact
P population density people/area A
affluence avg resource use/person T
technology effects of technologies used
to provide consume each unit of
resource
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P number of people per area A affluence or
average resource-use per person T technology or
the beneficial harmful environmental effects of
the technologies used to provide consume each
unit of resource
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Projected Population Growth
N Amer
Latin Am Carib
Europe
Asia Oceania
Africa
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Stabilization ratio crude birth rate/crude
death rate
SC Amer
Africa
Devg
Asia
Devd
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Concerns about Growth Limitations?

• Varying Perspectives
• Overpopulation causes resource depletion and
  environmental degradation
• Human ingenuity and technology will allow us to
  overcome any problems - more people may be
  beneficial
• Resources are sufficient to meet everyone's needs
  - shortages are the result of greed, waste, and
  oppression

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Decisions on how many children to have are
influenced by many factors, including culture,
religion, politics, need for old-age security,
and immediate family finances.
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Human Demography

• Demography - vital statistics about people, such
  as births and deaths
• Two demographic worlds
• Less-developed countries represent 80 of the
  world population, but more than 90 of projected
  growth
• Richer countries may even have negative growth
  rates

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Fertility and Birth Rates

• Fecundity - physical ability to reproduce while
  Fertility is the actual production of
  offspring
• Crude birth rate - of births per year per
  thousand people
• Total fertility rate - of children born to an
  average woman during her reproductive life(world
  avg 2.7 2.1 is required for replacement)
• Zero population growth (ZPG) occurs when
  births immigration deaths emigration

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Two demographic worlds
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By 2050, India will probably be the worlds most
populous country.
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Regional Declines in Total Fertility Rates
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Population Growth -Opposing Factors

• Pronatalist pressures
• Factors that increase peoples desires to have
  children (eg, enjoy family, children help w/
  earnings, high death rate, help when older,
  males valued, male pride, etc)
• Birth reduction pressures
• Factors that tend to reduce fertility (eg,
  educated women careers, higher family earnings,
  etc)

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Demographic Transition Accompanying Economic and
Social Development
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Demographic Transition

• Optimistic view - world population will stabilize
  during this century
• Pessimistic view - poorer countries of the world
  are caught in a "demographic trap" - helping poor
  countries will only further threaten the earth's
  resources
• Social justice view - overpopulation due to a
  lack of justice, not resources

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The Future of Human Populations
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As incomes rise, so does life expectancy.
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Birth Control Methods
Family Planning
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Infant Mortality and Women's Education
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Summary

• Role of Technology
• Two Demographic Worlds
• Fertility and Birth Rates
• Mortality and Death Rates
• Population Growth Factors
• Demographic Transition
• Future of Population Growth

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