HUMAN POPULATION DYNAMICS - MyTeacherPages by yurtgc548


									Population Ecology Part II
Thomas Malthus
 “diminishing returns”
He argues that rising wages and improved well-
being would lead to excess reproduction among
the working class.
A labor surplus would then cause wages to fall
below subsistence levels, resulting in
starvation, disease and crime.
In his view, land for food production was the
limiting factor in both population growth and
economic development.
Was Malthus Right?
     The Black Plague
Also called the “black death” or Bubonic
Deadliest pandemic in human history
1340’s and 1350’s
Thought to have been a bacterial
infection carried by fleas
Density dependent
Bubonic Plague
          mortality rate
          swelling in
          lymph nodes
          Turned black
Pneumatic Plague
           Caused a form of
           Same bacterium
           Victims died
           before reaching
           other places
Septicemic Plague
           100% mortality
           High fever
           Skin turned purple
The Catholic Church
 Lost prestige and spiritual
 Promised cures and treatments
 Said it was God’s will
 Could not explain so many
 People abandoned the church
  Effect on Europe
  Why has the human
population been able to
 continue exponential
  growth when other
populations would have
  leveled off by now?
Humans Have Been Able
      To Overcome
Environmental Resistance
  (Limiting Factors) to
     Sustain Growth
Arable Land
        Land that can
        be used for
        growing crops
        21% of
        surface is
Reasons for World Hunger Issues
  Unequal distribution of available food
  Loss of arable land
  Increasing population growth rate
  Increasing poverty in developing
    Arable Land
Assume no arable land is being
lost for the next 33 years.
2006, there was 1.15 acres of
arable land per person, world-
(i.e. 7.68 billion acres / 6.68
billion people).
        Arable Land
2039, there may be only 0.59 acres of
arable land per person, world-wide
i.e. 7.68 billion acres / 13 billion people
arable land is being lost at the
alarming rate of over24.7 million
acres per year.
  2039, there may be only 0.53 acres
of arable land per person, world-wide
Reasons for Loss of Arable Land
  Over exploitation for fuel wood
  Over farming (deplete nutrients)
  No rich sediment replacement due
  to flooding – controlled by dams
How have we still managed
to grow enough food to feed
the world?
Who grows most of the food?
What affect could global
warming have on this
Ways to Increase Crop Production
   Modern farm equipment
   Return nutrients to soil
   New genetically modified crops
Strategies for ensuring adequate
nutrition for a growing population:
   Increase the number of new food crops
   from a diversity of plant species
   Distribute food more equitably
   Increase land are that is dedicated to
   grain production rather than meat
   Assist developing countries in efficient
   crop irrigation systems.
How many people can
 the earth feed on our
     arable land?
What about over-fishing
      our oceans?
  What is the earth’s
  carrying capacity?
Factors Affecting
Human Population Size
#1 – Birth vs. Death Rates
  Birth rate - # live births per 1,000
  Death rate - # of deaths per 1,000
  Top 5 most populated countries:
  China, India, U.S., Indonesia, Brazil
Annual Rate of Natural Population
         Change (%)=

     Birth rate – Death rate
           1,000 people      x   100
  #2 - Fertility Rate
# children born to a woman in her
 Replacement-level fertility rate = #
 children a couple must have to
 replace themselves (2.1 to 2.5)
 Total fertility rate = average #
 children a woman has during
 reproductive years (global average is
 2.7, developed countries 1.6)
#3 – Factors Related to Children
  Importance of children to labor
  Cost of raising and educating a
  child ($250,000 in U.S. to age
  18 vs. minimal in developing
#4 – Religion and Culture
View of the family
Rights of women
Beliefs concerning birth control
Age at marriage
Sex preference for children
   #5 - Pension System
If retirement plans are available
and adequate – less children
No retirement – more children,
particularly males to support
them in old age
  #6 - Urbanization
Better access to family planning
More job opportunities
Higher standard of living
All generally promote smaller
#7 – Opportunities for Women
  Family Planning options
  Job opportunities
  Best way to reduce fertility
#8 – Infant Mortality Rate
  Better medicine and health care
  = lower infant mortality
  The more likely infants are to
  survive, the more fertility rates
#9 – Average Age at Marriage
  Developing countries = 14 or
  Developed countries = 25
#10 – Life Expectancy
Rapid rise in world population in
last 100 years is due to increased
life expectancy
Modern medicine means infants do
not die and people live to much
older ages
67 years globally, 78 years in U.S.
Poorest countries with HIV = 49
What factors affect death rates?
1. Increased food supplies and distribution
2. Better nutrition
3. Improvements in medical & public health
   technology (ex. immunizations and
4. Improvements in sanitation & personal
5. Safer water supplies to stop spread of
   infectious disease
 #11– Net Migration
Immigration vs. Emigration
Countries like the U.S. continue
to grow due to Immigration
Countries like Russia are
decreasing due to emigration
#12 – Age Structure
Growth Rate- includes birth rate, death
rate, immigration and emigration

Gross National Product- The most
commonly used measure of the
economic growth of a country.
  Population Change
    Growth Rate
Population change = (Crude birth rate
+ Immigration) – (Crude death rate +
If a population of 10,000 experiences
100 births, 40 deaths, 10 immigrants
and 30 emigrants in a year, what is the
net annual percentage growth rate?
(100 + 10) – (40 + 30) = 40
40/10,000 X 100 = 0.4%
Zero Population Growth- When the
number of births, equals the number of
deaths. No growth in the population.

Rule of 70’s – Doubling Time
Doubling time - # years it takes a
population to double
70/ growth rate = doubling time (daily)
72/ growth rate = doubling time (years)
If a population of a country grows at a
rate of 5% a year, the number of years
required for the pop to double is what?
Demographics of
Developing Countries-
 China is the largest but has taken drastic
 population control methods.
 By 2050, India is predicted to pass it.
 Pakistan is projected to become 3rd with
 Iran and Ethiopia following.
 However, Russia is losing 600,000 people
 a year, after being the 4th largest country
 in 1950. This is because of environmental
 pollution, hyperinflation, crime, corruption,
 disease and despair.
Developed countries
   Usually don’t have such
   population problems. It can
   be linked to poverty level
   even in developed countries.
Demographic Transition
   As countries becomes
industrialized their birth rates
Harsh living conditions lead to a
high birth rate and high death
rate. Thus, there is little
population growth.
As industrialization begins, food
production rises and health care
Death rates drop and birth rates
remain high
The population grows rapidly
Industrialization is wide spread
Birth rate drops and eventually approaches the
death rate.
This is because of:
    better access to birth control
    decline in the infant mortality rate
   increased job opportunities for women
   the high cost of raising children who don’t
   enter the work force until after high school or
Reasons human population growth has
 been so dramatic in the last century
  The Industrial Revolution
  Modern Medicine
 The birth rate declines even further,
 equaling the death rate and thus
 reaching zero population growth.
 Then, the birth rate falls below the
 death rate and the total population
 size slowly decreases.
  37 countries have reached this
stage. (mainly in W. Europe)
  To most population experts, the
challenge is to help the remaining
88% of the world to get to this
Demographic Transition
Demographic Transition in Japan
U.S. Statistics
 Because of the ‘Baby Boom’ the US
 has a bulge in the pyramid with
 people in their 50’s-60’s.
 There are also more women than
 men in the older age group because
 of differences in longevity between
 the sexes.
  The US has a high % of retired
people because of long life
expectancy. This makes us realize
the importance of social security,
 The US is considered a slow
growth population.
Some countries, including China, penalize
  couples who have more than one or two
  children by:
1. Raising their taxes
2. Charging other fees
3. Eliminating income tax deductions for a
   couple’s third child
4. Loss of health-care benefits, food allotments
   and job options
In China couples who pledge to have no more than
   one child receive
1. Extra food
2. Larger pensions
3. Better housing
4. Free medical care
5. Salary bonuses
6. Free school tuition for their one child
7. Preferential treatment in employment when their
   child enters the job market.
However, according to some studies,
  there is a strong preference for male
1. Girls are aborted at a higher rate than
2. Some infant girls are killed
3. Male children sometimes are fed better
   than female children.
     Environmental Impact Equation
          (Paul Ehrlich Formula)

Population X affluence X technology =
        Environmental impact
Developed Countries
 High rates of resource use
  Result in high levels of pollution and
 environmental degradation per
  These are believed to be the key
 factors determining overall
 environmental impact.
It is estimated that a US
citizen consumes 35 X’s as
much as the average citizen of
India and 100 X’s as much as
the average person in the
world’s poorest countries.
  Thus, poor parents in a
developing country would
need 70-200 kids to have the
same lifetime environmental
impact as 2 typical US kids.
 Urban areas must import food, water,
energy, minerals, & other resources.
  They produce enormous quantities of
wastes that can pollute the air, water &
  44% of the world’s people live in urban
areas that occupy only 5% of the world’s
land & they consume 75% of the world’s
1994 Global Summit on
Population & Development
Cairo, Egypt
Encouraged action to stabilized the
world’s population at 7.8 billion by
2050, instead of the projected 11-
12.5 billion.
The major goals are to:
 Provide universal access to family-planning
 Improve the health care of infants, children &
 pregnant women
 Encourage development of national population
 Improving the status of women by expanding
 education & job opportunities
Major goals continued:
Increase access to education for girls
Increase men’s involvement in child-
rearing responsibility & family planning
Take steps to eradicate poverty
Reduce & eliminate unsustainable
patterns of production & consumption.

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