POPULATION
Earth has ~7 billion people & is adding 10K/hr; 90% of the growth is in developing countries
Population is a function of: disease, war, famine, social traditions, individual’s morals, social
mores, religion, etc.
Demography - study of population characteristics (age, gender, occupation, fertility, etc.)
~75% of world’s population live on only 5% of Earth’s surface
Most population lives between 10N & 55N
Population is clustered in 5 Regions:
1) East Asia (1/4 of world’s people of which 5/6 live in PRC); mostly farmers
2) South Asia (1/4 of world’s population); mostly farmers
3) Southeast Asia (4th largest population cluster); mostly farmers
(#’s 1, 2 & 3 makeup > 1/2 world’s population but live on < 10% of Earth’s land area)
4) Europe (1/9 of world’s pop.; 3rd largest population cluster); mostly urban
5) Eastern North America (~ 2% of world’s population; northeast US & southeast
Canada); mostly urban
Similarities
1) most live near an ocean or river
(~2/3 of world’s population live within 500 km of an ocean & 4/5 live within 800 km)
2) low-lying areas
3) fertile soil
4) temperate climate
5) northern hemisphere
6) between 10N & 55N (except for part of Southeast Asia)
Areas Avoided
1) Dry Lands
2) Wet Lands
3) Cold Lands
4) High Lands (exceptions exist, ex: Mexico City which is at 2243 m (7360 ft))
Density - frequency with which something occurs in space
Population (Arithmetic or Crude) Density - number of people divided by a given
land area; this answers the where question
Physiological Density - total # of people divided by total arable land; helps answer why
Measures of Population Change:
1) Crude Birth Rate (CBR) - total live births per year per 1000 people; world CBR =
22/1000
2) Crude Death Rate (CDR) - total deaths per year per 1000 people; world CDR = 9/1000
3) Natural Increase Rate (NIR) - percentage by which a population grows in a year;
CBR - CDR (after first converting to percentages)
- world average 1.2%/yr
Total Fertility Rate (TFR) - average number of children a woman will have throughout
her child bearing years (~ 15 - 49 yrs)
- 2nd ½ of ‘90s, world TFR = 2.8, Africa TFR = 5.2, Europe TFR = 1.4
Exponential Growth & Doubling Time
- when something grows at a fixed percent per year, the growth is said to be exponential.
The important point is that the time required for the growing quantity to increase its size by a
fixed fraction is constant. Also, the time required for a quantity to double is also constant. Thus,
Time required for an exponentially growing quantity to double or the
Doubling Time = 69.3/ percent growth per unit time; in one doubling time, we have more
than all that had existed in all preceding growth; results in a J-curve.
Tripling Time = 110/ % of net increase; Ten Times = 230/ % of net increase
For ~ 290,000 yrs, human population doubled about every 35,000 years
1 AD - 1650: 1650 yrs
1650 - 1804: 154 yrs
1804 - 1927: 123 yrs
1927 - 1974: 47 yrs
In 1963, NIR = 2.2%, so D.T. = 31.5 yrs, today the NIR = 1.2%, so D.T. = 57.8 yrs
This rapid growth over the past 100 yrs was not due to a rise in birth rates but rather to a decline
in death rates due to:
1) increased food supplies
2) better food distribution
3) better nutrition
4) disease reduction
5) improved medical & health care
Likewise, longevity has little effect on population size, the major factors are how many children
are born & how many of them reproduce.
Population Growth Forecast
PFUTURE = PPRESENT x (1 + A)time, where A = percent of net increase as a decimal
Demographic Transition
- process of change in a society’s population from a condition of high CBR & CDR &
low NIR to a condition of low CBR & CDR, low NIR, & higher total population
Demographic Transition Stages
Stage I - Low Growth or Early Stationary (aka pre-industrial)
high birth rate: 35-50/1000
high death rate: 30-45/1000
growth rate: < 0.5%
ex: 1750 U.S., no country today
Stage II - High Growth or Early Expanding (aka transitional)
high birth rate: 35-45/1000
falling death rate (due to medicine): 15-20/1000
growth rate: > 2-5%
ex: early 1800s U.S., Cape Verde, 65-68% of all countries
Stage III - Moderate Growth or Late Expanding (aka industrial)
falling birth rate (due to smaller families): 15-25/1000 &
still falling death rate: 10-15/1000
growth rate: 1-2%
ex: late 1800s U.S., Chile, 15% of all countries
Stage IV - Low Growth or Late Stationary (aka postindustrial)
low birth rate: 0-10/1000
low death rate: 5-10/1000
growth rate: 0.5-1%
ex: present U.S., Denmark, 15-20% of all countries
Shape of the Population Pyramid relates to the growth stage
Zero Population Growth (ZPG): NIR = 0; sometimes applied to Stage 4 countries
Question: What country has a zero birth rate?
Answer:
World Population Growth was caused by:
1) Agricultural Revolution ~8000 B.C. when humans first domesticated plants & animals
2) Industrial Revolution ~ late 18th C. which increased wealth &, in turn, made communities
healthier places to live by increasing sanitation & hygiene
3) Medical Revolution - late 19th C. (diffused to LDCs in second 1/2 of 20th C.) which
eliminated many diseases