The world’s population is projected to increase
from 7.2 billion to over 9 billion between 2015 and 2050
The continued debate is one of the most
important and controversial issues in environmental science
Population growth Economic growth Politics
Definition: the study of human
populations, their
Statistics about people, such
as births, deaths, and where
they live as well as total
population size
Population density: the number of individuals in a population found in a particular area or
volume
A population’s density can affect how rapidly it can
grow or decline
e.g. biotic factors like disease
Some population control factors are
not affected by population density
e.g. abiotic factors like weather
Density Dep
endent Fa
ctor
Density In
Population
increases
because of
births
and
immigration
and
decreases
through
deaths
and
emigration
Instead of using raw numbers, crude
birth rates (
natalities
) and crude death
rates (
mortalities
) are used
Based on total number of births or deaths
The average number of children that a woman bears has dropped sharply
This decline is not low enough to stabilize the world’s population in the near future though
Total fertility rate (TFR): the average number of
children a woman has during her reproductive years
Replacement-level fertility: the number of
children a couple must bear to replace themselves
Slightly higher than two children per couple
WHY
?
Infant Mortality Rate
-Number of infant deaths per 1000 who pass away before their 1st birthday
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?
Growth Rate =
Population Change / Total Population
40
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 natural growth rate?
60
If a population of 20,000 experiences has a annual birth rate of 0.8% and a death rate of 1.2%, what is the annual natural growth rate?
If a population of 500 grows at a rate of 5% a year, how large would the population be in 30 years?
If a population of 500 grows at a rate of 5% a year, how large would the population be in 30 years?
RULE OF 70!!!!
Doubling Time
=
70
/
Rate
70 / 5% = 14 years to double
original population x 2
# of times it doubles If a population of 200 grows at a rate of 2% a year, how large would the population be in 36 years?
RULE OF 70!!!!
Doubling Time
=
70
/
Rate
If a population of 502 rats doubled in 10 days, what is the growth rate for this rat
population?
RULE OF 70!!!!
Doubling Time
=
70
/
Rate
10 days = 70 / rate
7%
daily
The human population has grown rapidly
because of the expansion of agriculture
and industrial production and lower death rates from improvements in hygiene and medicine.
In 2006…
Developed countries grew exponentially at 0.1%
annually
Developing countries grew 15x faster at 1.5% per
There are likely to be between 9-11 billion people on earth by 2050.
U.N. world population projection based on women having an average of 2.5 (high), 2.0 (medium), or 1.5 (low) children.
97% of growth from
developing countries living in acute poverty
No population can increase its size
indefinitely
Intrinsic rate of increase: the rate at which
a population would grow if it had unlimited
resources
Carrying capacity: the maximum
population of a given species that a
particular habitat can sustain indefinitely without degrading the habitat
Maximum reproductive rate of an
organism
EX: Common housefly can lay 120 eggs in each
generation. If nothing hurt the eggs or the flies, in 7 generations there would be 6,182,442,727,320 flies
Live 15-30 days Maggot to adult in 10 days
If there was a continued
growth and not enough
death, food would run short
and available space would
run out
How does human
reproduction rate help slow
population growth?
Wrote An Essay on the Principle of Population Summarized as “Diminishing Returns”
Population growth will naturally check itself
Rising wages and improved well-being
excess reproduction among the working class a labor surplus
wages fall causing starvation, disease and crime In his view, land for food production was the
limiting factor in both population growth and economic development
Some species maintain their carrying capacity by migrating to other areas
Over time species may increase their carrying capacity by developing adaptations
So far, technological, social, and other cultural changes have extended the earth’s carrying
Large number of
smaller offspring with little parental care (r-selected species)
Fewer, larger
offspring with higher invested parental
care ( K-selected species)
Different species vary in how long
individual members typically live
Anything that causes the population to
grow
uncontrollably
(EX: Baby boom… 78 million person
increase between 1946-1964)
The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion
Nearly 2.9 million people were added to the U.S. in 2006:
59% occurred because of births outnumbering
deaths
41% came from illegal and legal immigration
In 2006, the total fertility rate in the
United States was ~2.1
47 years
Homicides per 100,000 people Hourly manufacturing job wage (adjusted for inflation) Living in suburbs Homes with electricity Homes with flush toilets High school graduates Married women working outside the home
Life expectancy 1.2 5.8 $15 $3 52% 10% 99% 2% 98% 10% 83% 15% 81% 2000 1900 8% 77 years
Which are the most important changes in terms of population?
The number of children women have is
affected by:
The cost of raising and educating them Availability of contraception and abortion Education and employment opportunities Availability of pensions
Urbanization Infant deaths
Marriage age • Birth rates in urban areas usually are
3-4 X’s lower than in rural areas
• Why?
- Cities provide education opportunities - Less room for children
Death rates have declined because of:
Increased food supplies, better nutrition
Advances in medicine
Improved sanitation and personal hygiene
Safer water supplies
U.S. infant mortality is higher than it could be (ranked 46th world-wide) due to:
Inadequate pre- and post-natal care for poor Drug addiction
How fast a population grows or declines depends on its age structure
Prereproductive age: not mature enough to
reproduce
Reproductive age: those capable of
reproduction
Postreproductive age: those too old to
reproduce
The number of people younger than age 15 is the major factor determining a country’s population growth
Changes in the distribution of a country’s age groups have long-lasting economic and social impacts
32% of the people in developing countries were under 15 years old in 2006 versus only 17% in developed countries
If the number of births equals the number of
deaths, what occurs…
Populations with a large proportion of its people
in the preproductive ages (1-14) have a large
potential for rapid population growth.
Least Developed CountriesBirth rate exceeds the death rate Population is getting larger.
Pyramid shaped histogram.
Birth rate almost equals death rate Population doesn’t get larger / grows very slowly.
Histogram shape is more box-like until age 45-85. EX: US, Australia & Canada - slow
Birth rate is smaller than the death rate Population decreases.
Histogram bulges near the top (an inverted pyramid). EX: Germany, Bulgaria & Hungary
Demographic Transition
: As countries
become economically developed, their
birth and death rates tend to decline.
Preindustrial stage: little population
growth due to high infant mortality
Transitional stage: industrialization
begins, death rates drops and birth rates remain high
Industrial stage: birth rate drops and
approaches death rate
Postindustrial stage: birth rate is equal to
Harsh living conditions lead to a high birth rate and high death rate
As industrialization begins, food production rises and health care improves
Death rates drop and birth rates remain high The population grows rapidly
Industrialization is wide spread
The 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 college
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
China
is the
largest
but has taken
drastic
population control methods
India’s population will soon pass China’s
Indonesia, Nigeria and/or Pakistan is
projected to become 3
rd
However,
Russia
is
losing
600,000
people a year, after being the 4
thlargest
country in 1950
This is because of environmental pollution,
hyperinflation, crime, corruption, and
disease
For more than five
decades, India has
tried to control its
population growth
with only modest
success
Since 1970, China has
used a
government-enforced program to
cut its birth rate in
half and sharply
reduce its fertility rate
Total fertility rate Percentage of world population Population Population (2050) (estimated) Illiteracy (% of adults) Population under age 15 (%)
Population growth rate (%)
17%
20% 1.1 billion
1.3 billion
1.6 billion India China
GDP PPP per capita Percentage living below $2 per day
Life expectancy 47% 17% 36% 20% 1.6% 0.6% 1.4 billion $5,890 $3,120 47 80 70 years 62 years 27 58
1.6 children per women (down from 5.7 in 1972) Infant mortality rate
Poor planning
Bureaucratic inefficiency Low status of women
Extreme poverty
Lack of administrative financial support Disagreement over the best ways to slow
population growth
Prohibition of Child Marriage Act (2006) 18
Currently, China’s TFR is 1.6 children per women
China has moved 300 million people out of poverty
One child policy applied to registered urban residents (allowed 1 child/10 years)
Problems:
Tends to lead to gender imbalance
Since there is a strong preference for
male children:
1.
Girls were aborted at a higher rate than
boys
2.
Some infant girls were killed
3.
Male children were sometimes better fed
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
A Closer Look At China’s Plan to
Slow Population Growth
In China, couples who pledged to have no more than
one child received:
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
Environmental Impact =
(Population) (Affluence)
(Technology)
In developing countries…
Slums fecal snow disease
Not a problem in the US because of better working
and housing conditions, as well as, air and water quality being improved
In developed countries…
Urban areas must import most of its food, water,
energy, minerals, & other resources producing
enormous quantities of wastes that can pollute the air, water & land
High rates of resource use
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
Results in high levels of pollution and environmental degradation per person
Unequal distribution of available food Loss of arable land
Increasing population growth rate
Increasing poverty in developing countries
Increase the number of new food crops from a diversity of plant species
Distribute food more impartially
Increase land are that is dedicated to grain production rather than meat production
Assist developing countries in efficient crop irrigation systems
Family planning has been a major factor in reducing the number of births and abortions throughout most of the world
Women tend to have fewer children if they are…
–???
Educated
–
Hold a paying job outside the home
The best way to slow population growth is a combination of:
Investing in family planning Reducing poverty
Cairo, Egypt
Encouraged action to stabilized
the world’s population at 7.8
billion by 2050, instead of the
1994 current projected 11-12.5
billion
Provide universal access to
family-planning services
Take steps to eradicate poverty
Improve the health care of infants, children &
pregnant women
Encourage development of national
population policies
