Transcript Human Population

Population Clock
• http://www.worldometers.info/worldpopulation/
Human Numbers Through Time: A.D. 0
Taken from Nova online
300 million
A.D. 1000
310 million
1800
1 billion
65% Asia, 21% Europe, 1% North America
1927
2 billion
1960
3 billion
1974
4 billion
1987
5 billion
1999
6 billion
62% Asia, 12 % Europe, 12% Africa, 9% Latin America,
5% N. America
2050
Population will more than likely will reach 9 billion people
Nearly all growth will take place in developing countries
Graph of human population growth
• Place time on the horizontal axis (range 1600-2050)
• Place number of people on the vertical axis (range 0-20 billion)
Year
Number
(billions)
Year
1650
1750
1850
1925
1956
1966
1970
.50
.70
1.0
2.0
2.5
3.3
3.6
1974
1976
1980
1991
2000
2004
2011
Number
(billions)
3.9
4.0
4.4
5.5
6.0
6.4
7.0
Questions in your journal
1. If it took 1649 years for the world population to
double (from .25 billion people to .50 billion).
How long did it take for the population to
double once again
2. How long did it take for the population to
double a second time? A third time?
3. Based on your graph, in what year will the
population reach 8 billion?
4. Based on your graph, how many years will it
take for the population of 2004 to double?
PGR: increase in a country’s population
during a period of time (1 year).
PGR = birth rate – death rate
+
+
immigrants
emigrants
Average Annual Population Growth Rate, 1980-98
Rapid PGR: Africa and Middle East
Slowest PGR: Europe and North America
Population (shown in millions)
1980: 4.4 Billion
2000: 6 Billion
In the past few decades…
• Death rates have declined
– Living longer in both industrial and developing countries 
immunization, health care, technology
– Avg life expectancy: 78
• Birth rates have declined
– Parents are choosing to have less children
– Access to family planning
– More women starting families later in life
* PGR remain high though because birth rates have not fallen as
much as death rates
Population Growth Rate
• PGR have started to decline
• But will continue to increase because the population
base has become larger.
• Growth rates tend to be higher in low and middleincome
Population momentum
• Phenomenon that occurs when a large proportion of a country’s
population is of childbearing age.
• Occurs in low-income countries
• More than a third of the population is under the age of 15
Why so many children?
• Fear their babies may die
• Need laborers to work
• Ensure that they themselves will be
cared for in their old age
• Lack access to education and to
family planning
To reduce fertility rates
1. Greater access to primary health
care and family planning services
2. Receive a basic education (esp. girls
and women)
3. Have government serviced that help
protect them when sick, old,
unemployed
Are we going to reach a
carrying capacity?
• Carrying capacity: number of individuals
the environment can support over a
long period of time
• Some say we have already exceeded the
carrying capacity
• Others say billions more can be sustained on
earth
• Consensus
– World population will continue to grow until after
the middle of this century
– Peak of some 9 billion
– Perhaps declining in the latter years
What controls population size?
• Density-Independent Factors
– Weather, floods, fire
– Reduce population by the same proportion
regardless of size
• Density-Dependent Factors
– Shortages of food, shelter
– Triggered by increasing population density
In groups of 2 or 3, answer the
following (in complete sentences)
1.
2.
3.
4.
What do you think daily life might be in your town in 2050
when there are 9.2 billion people on this planet?
What types of technological changes will be needed to
accommodate the world’s growth?
What do you think will be the greatest environmental
concerns at that time?
Do you see population growth becoming a major political
issue by 2050? Why or why not? What types of
population issues might people be talking about at that
time?