Week 5:
Human population as environmental factor
• Supplement—Latitude and Longitude
• Chapter 5 B&K
• Rates of growth
• The prophecy of Malthus and quality of life
• Population growth and exponential growth
• The logistic growth curve and human population
• Limiting factors
• Age Structure
• Fertility rates and life expectancy
• Controlling population growth
Ward Island as a System
Shape of the Earth
We think of the
earth as a sphere
It is actually a spheroid,
slightly larger in radius at
the equator than at the poles
Cutting Plane of a Meridian
P
Prime Meridian
Equator
Meridian
Definition of Longitude, l
l = the angle between a cutting plane on the prime meridian
and the cutting plane on the meridian through the point, P
-150°
180°E, W
150°
-120°
120°
90°W
(-90 °)
90°E
(+90 °)
P l
-60°
-30°
-60°
30°
0°E, W
Definition of Latitude, f
m
O
q
f
S p
n
r
(1) Take a point S on the surface of the ellipsoid and define
there the tangent plane, mn
(2) Define the line pq through S and normal to the
tangent plane
(3) Angle pqr which this line makes with the equatorial
plane is the latitude f, of point S
Latitude and Longitude on a Sphere
Meridian of longitude
Z
Greenwich
meridian
l=0°
N
Parallel of latitude
P
•
W
•
•
X

O
l
Equator
R
=0°
•
E
l - Geographic longitude
 - Geographic latitude
Y
R - Mean earth radius
O - Geocenter
Earth to Globe to Map
Map Scale:
Map Projection:
Scale Factor
Representative Fraction
= Globe distance
Earth distance
(e.g. 1:24,000)
=
Map distance
Globe distance
(e.g. 0.9996)
Definition of Elevation
Elevation Z
P
•
z = zp
z = 0 Land Surface
Mean Sea level = Geoid
Elevation is measured from the Geoid
Cylindrical Projections
(Mercator)
Transverse
Oblique
Longitude was a major problem of the
1700’s
• Although the shape of the
world was reasonably well
known, and latitude could
be calculated from the
angle of the sun at noon,
mariners could not
calculate their longitude.
• The British government
offered a huge prize
(£20,000) for a solution in
1714.
• The prize was claimed in
1760 by John Harrison,
who invented the modern
timepiece.
Prophecy of Malthus
• English clergyman & economist (1766-1834) derives
his “prophecy from two postula:
• First, That food is necessary to the existence of
man.
• Secondly, That the passion between the sexes is
necessary and will remain nearly in its present
state.
The prophecy
• Famine seems to be the last, the most dreadful
resource of nature. The power of population is so
superior to the power in the earth to produce
subsistence for man, that premature death must
in some shape or other visit the human race. The
vices of mankind are active and able ministers of
depopulation. They are the precursors in the great
army of destruction; and often finish the dreadful
work themselves. But should they fail in this war
of extermination, sickly seasons, epidemics,
pestilence, and plague, advance in terrific array,
and sweep off their thousands and ten thousands.
Should success be still incomplete, gigantic
inevitable famine stalks in the rear, and with one
mighty blow levels the population with the food of
the world.
Environmental Problems
What’s your top priority?
•
•
•
•
•
•
•
Climate Change
Biodiversity
Air pollution
Water pollution
Solid waste
Loss of wilderness
Six Billion Human Beings
(explore world population growth)
Total Fertility Rate (TFR)
• The average number of children expected
to be born to a woman during her lifetime.
• Note that demographers and population
scientists usually express population size as
the number of females in a population and
ignore males.
• How do social practices affect fertility?
– For example: polygamy in Arab countries, among
early Mormans?
– For example: preference for males in China?
• Six Billion Human Beings
(learn about TFR)
Basic Concepts
• Rates of Growth
– Growth rates—inversely related to a nation’s per capita
income; positive feedback loop  increasing poverty.
• Populations, Density, and Consumption (technology)
– Population impact: number of people and environmental
impact per person.
– Total environmental impact of a population = number of
people (population) x impact per person (Consumption &
technology); raising either variable increases the total
impact.
– Impact depends on consumption rates and population
density.
– Dense populations have large local impact.
– Consumptive populations have large global reach and
utilize vastly more resources.
Human Population Eras
• Early hunter-gatherers ~few million people.
Growth rate <0.0001%
• Early agriculture – first rise of population.
Growth rate ~0.03%
• Industrial revolution – improvements in
health care & food supply lead to sharp
increase in human population.
Growth rate ~0.1%
• Today – slowing rate of population growth
for Europe and U.S., rapid in Asia, Africa,
South America. Growth rate 1.4-2%
Population dynamics
• The crude birthrate of a population is the number
of births per 1000 individuals in a population.
• The crude growth rate is the crude birthrate
minus the crude death rate, or the net change in a
population of 1000 over a year.
• Maximum lifetime is the maximum possible age
for an individual of a species.
• Life expectancy is the average remaining years of
an individual at a given age; it is often used to
refer to the average lifespan of individuals in a
population.
1.
2.
3.
4.
Quiz 5a
Assume that the rate of increase for goats is 14% per
year. At this rate, if Mr. Champini’s herd of 150 goats
had not been stolen by bandits, it would have increased
to how many after 5 years? a) 2,521,018; b) 200; c)
3000; d) 300; e) 600.
The Geographic Positioning System uses what principle
to locate objects on earth? a) synchronized detection of
laser pulses; b) radio signals from an array of
transmitter towers; c) precise measurement of distance
to satellites whose exact orbit is known; d) receivers in
a series of satellites detect the GPS position and
transmit it back to the user; e) position of celestial
bodies such stars and planets.
The prophecy of Malthus predicts that human population
will increase without limit until all only humans remain on
Earth. a) True; b) False.
A major cause for population increase has been: a) rising
birth rates; b) falling death rates; c) rising birth rate &
falling death rate; d) improved educational; e) none of
these
Differences in causes of death
Equations of Population Change
• Population size
P2 = P1 + (B – D) + (I – E)
• Growth rate
g = (B-D)/N (Births-Deaths)/Number of people
• Exponential growth & doubling time
Pt = P0 exponent gt
Doubling time = 70/g%
• If world growth rate is 1.75%,
doubling time is 70/1.75 = 40 years
Demographic Changes Among Regions
• Modern history is
dominated by population
shifts—Do consumption
patterns match?
Total Fertility Rates and Pop. Growth
• Population growth
depends more on
TFR than life
expectancy.
• However, survival to
child-bearing ages is
a crucial factor.
• The TFR in future
populations will have
major impact on
population growth.
Different rates, different outcomes
Demography
• Age Structure
– Numbers of people and gender balance
•
•
•
•
•
•
Demographic transition (rem logistic curve)
Total Fertility
Population and environment
Death rate and environment
Population change and standard of living
Six Billion Human Beings
(learn about age structure and survival rates)
Population structure
Replacement-level fertility and momentum
• The TFR required for a
population to remain
constant is about 2.1
children/female.
• Even if birth rates are
declining in a
population, population
momentum will cause
population to grow
after replacementlevel TFR is achieved.
• Why?
Pop. Growth and the Logistic Curve
• The logistic curve
predicts that growth will
slow as a population
approaches its carrying
capacity.
• Change from increase to
maintenance rates of
growth called
demographic transition.
• Can this information be
used to predict eventual
size of human
population?
Demographic Transition
• Note that limits to human population levels reflect
societal choices rather than limiting factors that
control wildlife populations.
• What limits do affect population growth?
Demographic transition
The Carrying Capacity of Earth
• Improving the standard of living in poor
countries by traditional means may negate
the benefits of controlling population
growth. Why?
• Earth’s maximum sustainable human
population cannot be calculated without
making value judgments about the quality of
life we desire for that population.
• To what degree do Earth’s populations
(nations or societies) compete for
resources?
Limiting Factors
 Limiting factors are those which limit
population growth; they may be short-term
(limiting growth within one year of
occurrence), intermediate-term (limiting
growth after one year but before 10 years
of occurrence) or long-term (limiting
growth ten or more years after occurrence).
Limiting factors cont.
 The food supply is the resource most susceptible
to constraint by short-term limiting factors.
Some forms of pollution, energy shortages,
desertification, and disruption in supply of
renewable and non-renewable resources are
examples of intermediate-term limiting factors.
• Long-term limiting factors include soil erosion,
groundwater depletion, and global climatic changes
and pollution effects.
 The declining per capita availability of certain
biological resources suggests a human population
near or beyond its current long-term carrying
capacity.
Limits to Growth
• Food supply:
– 1984: 346 kg per capita
1994: 311 kg per capita
• Land/soil resources
– Decline since 1954 to 1.7 ha per capita
– Predict in 2050 1.0 ha per capita
• Water resources
– 350 to 1000 l/day developed countries – 2 to 5 l/day in
developing countries
• Population density
–
–
–
–
source http://www.photius.com/wfb1999/rankings/population_density_0.html
Hong Kong: 6,570 people/km2
Netherlands: 466 people/km2
Africa (all): 66 people/km2
United States: 30 people/km2
China
•
•
•
•
•
•
Population: 1.25 billion
134 people/km2
Birth rate: 1.5%
(U.S. 1.4%)
One-child policy
Rapid economic growth
• China is now
experiencing a
demographic bonus due
to having a high
proportion of productive
adults relative to
children.
• As China changes its
standard of living,
resource usage—
particularly water use—
will have a profound
impact.
• Aging, gender balance
and population growth
will remain important
issues.
• Six Billion Human Beings
(Check current population size)
Quiz 5b—pg 1
Choose the best suited answer to questions 1-3 from concepts a-e.
1) The s-shaped curve according to which a
population grows rapidly but eventually
reaches a constant population:
a) demographic transistion
2) The maximum number of a particular
species that an environment can support
without degradation to the environment:
b) replacement fertility
curve
3) The movement of a nation from a high
population growth to a low population growth:
c) logistic growth curve
d) sustainablity
e) carrying capacity
Quiz 5b—pg 2
55 +
50-55
45-50
40-45
35-40
30-35
25-30
20-25
15-20
10-15
5-10
0-5
Female
Male
16
12
8
4
0
4
8
12
16
Percent of the population
4) The figure above illustrates which of the following concepts: a) replacement
level fertility; b) population age structure
c) low death rates; d) Malthus’ theory of human population; e) logistic population
growth
5)Assume that the figure above illustrates the characteristics of a tribe on a small
Pacific island. Which of the following is a plausible explanation for the shape of
the graph: a) a devastating drought about 10 years ago; b) the arrival of a clan
from another island about 20 years ago
c) introduction of prenatal and infant medicine about 10 years ago; d) many of the
island elderly moved to another island about 5 years ago; e) a record crop harvest
about 5 years