Published on: Mar 4, 2016
Transcripts - Polulation2015(LorenEdit)
There is no exception to the
rule that every organic
being increases at so high a
rate, that if not destroyed,
the earth would soon be
covered by the progeny of a
We have an over population
problem and something needs to
be done to solve it.
A. Strongly agree
E. Strongly Disagree
Starts breeding when 30 years old
Breeds until 90 years old
Has three pair of young
At the end of 500 years
15 million elephants
Even slow breeding man has doubled
in twenty-five years, and at this rate,
in a few thousand years, there would
literally not be standing room for his
World Population Estimates
1804 1 billion
1927 2 billion
1960 3 billion
1974 4 billion
1987 5 billion
1999 6 billion
2011 6.9 billion
2050 9 billion ????
Human Population Growth
Population Density (persons /
Dynamics of Population Growth
Growth - Growth at
a constant rate of
increase per unit
• Arithmetic Growth -
Growth at a
per unit time.
• The maximum number of individuals of any species that
can be supported by a particular ecosystem on a long-
• All the limiting factors that tend
to reduce population growth
rates and set the maximum
allowable population size or
carrying capacity of an
• Until the Middle Ages, human
populations were held in check by
diseases, famines and wars, and thus
grew very slowly.
– It took all of human history to reach 1
– 150 years to reach 3 billion
– 12 years to go from 5 to 6 billion
• Human population tripled during the
• For most of our history, humans have not been very
numerous compared to other species.
• Before the invention of agriculture only a few million
humans existed on the planet.
• By 5000 BC the world population expanded to about 50
• By the first century AD the population reached 300 million.
• Until the middle ages the human population was held in
check by diseases, famines and war.
Human Population Growth
• By 1650 the world population was about 600
• After 1650 -- the age of science and the beginning
of modern transportation, technology and
communication -- the population has increased
• In 2006 we had a world population of ~6.5 billion.
• Will this explosion of growth continue until we
overshoot the carrying capacity of our
environment (if we have not done so already) and
result in a catastrophic dieback?
Blip on human trajectory
Scenario 1: BAU population growth (constant 2013 age-specific vital
Scenario 2a: reducing mortality, increasing age at primiparity,
declining fertility to two children per female by 2100;
Scenario 2b: same as Scenario 2a but without reduced mortality;
Scenario5: avoiding all unintended pregnancies resulting in annual
births. High and low projections by the United Nations (12)are
shown as a grayed area, and the revised range for 2100
Scenario 6: elevated childhood mortality from climate change
Scenario 7: mass mortality event over a 5-y period starting 2056, equal to the
proportion of combined number of deaths from World War I, World War II, and
Spanish flu scaled to the mid-21st
Scenario 8: 2 billion people killed because of a global pandemic or war spread
over 5 y, starting midway (i.e., 2056) through the projection interval;
Scenario 9: 6 billion people killed because of a global pandemic or war spread
over 5 y and initiated one-third of the way through the projection interval (i.e.,
2041). The mass mortality windows are in-dicated as gray bars
Limits to Growth
• Thomas Malthus (1798) argued human
populations tend to increase exponentially
while food production is plentiful.
– Humans inevitably outstrip food supply and
• Human population only stabilized by positive checks.
• Humans are too lazy and immoral to voluntarily reduce
• Growing human populations will only stop growing when
disease or famine kills or when social conditions compel
others to reduce their birth rates.
• Population growth is a symptom rather than
a root cause of poverty and other social
– Real causes of these problems are exploitation and
– The earth is bountiful in its resource base, but
poverty and high birth rates results from oppressive
social relationships that unevenly distribute wealth
– The way to slow population growth and alleviate
many social problems is through social justice.
Malthus and Marx
The Role of Technology
• Technological optimists argue that Malthus
was wrong in his predictions because he
failed to account for scientific progress.
– Current burst of growth was stimulated by the
scientific and industrial revolutions.
– Progress in agricultural productivity, engineering,
medicine, sanitation, etc. have made it possible to
support more people.
– The burst of world population growth that began 200
years ago was stimulated by scientific and industrial
What would you consider
A. Malthusist (it’s a population problem)
B. Marxist (it’s a social problem)
C. Technological Optimist (wait, what problem?)
D. I don’t agree with any of these.
New wheat varieties and improved crop
management practices transformed
agricultural production in Mexico during
the 1940's and 1950's and later in Asia and
Latin America, sparking what today is
known as the "Green Revolution."
Can More People be
• More people mean larger markets,
more workers, and increased
efficiency due to mass productions.
• Greater numbers also provide more
intelligence and enterprise to
– Human ingenuity and intelligence.
• Highest population growth rates
Sub-Saharan Africa and the Middle East
◦ Niger, Yemen, and Palestine have an annual population growth rate is 3.2%.
◦ Less than 10% of all couples use any form of birth control, women average 7
children each, and nearly half of the population is less than 15 years old.
• Negative growth rates
– Italy, Germany, Japan, Hungary
– Average age is 40, and by 2050 life expectancy is expected to exceed 90. Many
couples have one or no children.
– Japan is predicted to shrink from 127 million to 120 million by 2050.
– Europe, which makes up 12% of the world population, is expected to drop to 7%
Africa’s population has tripled since 1960 and continues to
grow the fastest. Europe had twice as many people as Africa in
1960. By 2050 experts estimate there will be three times as
many Africans as Europeans.
Fertility and Birth Rates
Fertility rates have
declined in every region
of the world except Africa
over the past 50 years.
The greatest fertility
reduction been in
Southeast Asia, where
rates have fallen by more
The world as a whole has
an average fertility rate of
2.6 and growth rates are
now lower than at any
time since WWII.Average total fertility rates for less-developed countries
fell by more than half over the past 50 years. Progress
slower in least-developed countries, but by 2050, they
should be approaching the replacement rate of 2.1
children per woman.
Total Fertility Declines as
Women’s Education Increases
Birth Reduction Pressures
• Higher education and personal freedom
for women often result in decisions to
– When women have more opportunities to
earn a salary, they are less likely to have
– Education and socioeconomic status are
usually inversely related to fertility in
Literacy Rates (Females)
Population Growth Rates
Population Growth, Opposing
• Pronatalist Pressures
– Factors that increase the desire for children.
• Source of pleasure, pride, comfort.
• Source of support for elderly parents.
• Current source of family income.
• Social Status
• Replace members in society as they die.
–Boys frequently valued more than
Life Span and Life Expectancy
• Life expectancy- the average age that a
newborn infant can expect to attain in any
– The primary cause of most population growth
in the past 300 years has been declining
mortality, not increasing fertility.
– 1900- average World-wide life span was 30
2009- average World-wide life span was 67
Life Span and Life Expectancy
• In developing countries, higher
income often means families can
afford more children, thus fertility
• In less-developed countries, adding
another child to a family usually
does not cost much, while in
developed countries, raising an
additional child can carry significant
How many children are in your
A. I am an only child (1)
B. I have one sibling (2)
C. I have two siblings (3)
D. I have three siblings (4)
E. I have four or more siblings (5+)
Regions in the Process of
Crude Birth Rate - Number Births per thousand persons in a given year.
Crude Death Rate
Number of deaths
persons in a given
The Optimistic View
• Demographic transition is occurring in most
• Growing prosperity and social reforms that
accompany development reduce the need for large
• Technology transfer to developing countries is
progressing much faster than in the past.
• Developing countries have historical examples to
follow for population stability.
• Modern communications is a stimulus for change
The Pessimistic View
• The poorer countries of the world are caught in a
“demographic trap” that prevents them from
escaping from the present stage of demographic
• Their populations are growing so rapidly that
human demands exceed the sustainable yield of
local forests, grasslands, croplands or water
• The resulting environmental deterioration may
prevent the developing world from completing
• The developing world populations may continue to
grow until catastrophe intervenes.
Source - United Nations - 1992
Doubling Time of a population: 70/annual percentage growth rate. i.e. if
the annual percentage growth rate is 35%, a population will double
every 2 years.
Reduced Population Growth has
Both rapidly and slowly growing
countries can have a problem
with dependency ratio.
The number of non-working
compared to working individuals
in a population.
By 2050, the UN predicts that
there will be two older persons for
every child in the world.
Does this mean that some
countries should re-think their
population policies and/or offer
incentives for marriage and child-
Ice cubes, Frozen dinners, Green
beans, Spinach, or Eggs: Where is
your next food poisoning coming
A. Ice Cubes
B. Frozen Dinners
C. Green Beans