Human Population Growth
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Transcript of Human Population Growth
Basic concepts and human history
Human Population
Growth
Human population has recently exploded in sizeNote large increase in late 20th century
Homo sapiens sapiens (modern humans)
around 90,000 years old
Human ancestor numbers regulated by the environment
like any other organism
Changes in society cause changes inpopulation
Human evolution
Hunter-gatherers
Small nomadic populations
Short life expectancy (30-40 yrs.)
LOW ENVIRON. IMPACTS Small numbersFrequent movements
Began 10,000 - 12,000 y.a. in the Middle East
Fundamentally alters human civilization
Agricultural
revolution
Ample food available
Craftsmen and artisans arise
Class distinctions
Frees individuals from daily food gathering
Societal effects
Better survival rates
Permanent settlements arise... Architecture improves...
Agricultural revolution
...CITIES ARE BORN
POPULATION DENSITY: Populations remain in one locationAmple food = population growth
ENVIRONMENTAL IMPACTS: Increased human populations
stress local environment
PEOPLE IN CITIES NEED: Fields for farming & grazing, water,
wood, clay, minerals, etc.
This changes everything...
Menderes Valley in modern Turkey
Erosion in river valley
OvergrazingOver-farmingDeforestation
Delta into Aegean grows
over time
Begins in Europe in early 18th century
CHANGES Agriculture Production
Transportation
Industrial revolution
SOCIETY
STEAM POWER: Coal-fired
Replaces water powerFactories need not be near water
Powers factories, railroads, sea travel
Industrial revolution
AGRICULTURE: Crop rotation - reduced fallow time
END RESULT: More food from less land with less labor
Plowing and seeding techniques improvedRoot crops popularized
Late 1800's inorganic fertilizer producedMechanized farming and processing
Industrial revolution
SOCIAL CONSEQUENCES:
Urbanization of population
Plentiful foodMedicine and sanitation reduce mortality
END RESULT: Populations rise rapidly
Mass production improves quality of life
Industrial revolution
Num
bers
of h
uman
s
Time
Tool-making revolution
Agricultural revolution
Industrial –Scientific revolution
Each of these revolutions raised
the carrying capacity for humans
Revolutions and pop. growth
Time
Num
ber
Population grows slowly...
…then rapidly...
…eventually leveling off at the carrying capacity
CARRYING CAPACITYMaximum no. of a species
the environment can support
A highly simplified and somewhat unrealistic growth model
Population growth curve
Note the human population is
still in the rapid growth phase
Figure 3.12
THE BIG QUESTION: Where will the human population level off?
http://www.unfpa.org/modules/6billion/facts.htm
How many humans can the earth support?QUESTION:
Assumes:All open flat land cultivated
Purely vegetarian dietPeople live underground
Assumes:Current food production
Typical American diet
50 billion 2.5 billion
World grain production leveling offPopulation continues to increase
Per-capita grain production necessarily declines
Human carrying capacity
Environmental impact starting to cause problems
BIRTH RATE: Births per unit time divided by population size
b = B/N b = birth rateB = number of births per unit timeN = total population size
DEATH RATE: Deaths per unit time divided by population size
d = death rateD = number of deaths per unit timeN = total population size
d = D/N
GROWTH RATE: Rate of population change
g = (B - D)/N Variables as above
Calculating growth rate
Population of Australia in 1998 (N) = 18,700,000 Births from 1998-1999 (B) = 261,500 Deaths from 1998-1999 (D) = 130,900
BIRTH RATE: b = B/N b = 261,000/18,700,000b = 0.014b = 1.4%
d = D/NDEATH RATE: d = 130,900/18,700,000d = 0.7%
GROWTH RATE: g = (B - D)/N
g = (261,800 - 130,900)/18,700,000g = 0.7%
AN EXAMPLE:
Figure 5.5
Time it takes population size to
double
Varies depending on growth rate
Roughly equal to 70 growth rate
Even g =1% will double global
population in your lifetime
DOUBLING TIME
Pop sizetime 2 = Pop sizetime 1 + (Pop sizetime 1 * growth ratetime1)
N2 = N1 *(1+ g1)
Using the previous example: Population of Australia in 1998 (N1) = 18,700,000
Population of Australia in 1999 (N2) = ?
Growth rate of Australia in 1998 (g1) = 0.7% or 0.007
N2 = 18,700,000 *(1.000 + 0.007)
N2 = 18,700,000 + 130,900
N2 = 18,830,900
POPULATION GROWTH:
N2 = N1 *(1 + g1)
Population increase affected by population size and growth rate
Therefore: Large population = rapid increaseHigh growth rate = rapid increase
China = 1,220,000,000 people x 1% growth = +12,200,000 per yrJapan = 126,000,000 people x 1% growth = + 1,260,000 per yr
Population size
Japan =126,000,000 people x 1% growth = + 1,260,000 per yrJapan =126,000,000 people x 10% growth = + 12,600,000 per yr
Growth rate
FACTORS AFFECTING POPULATION GROWTH
The two worldsDEVELOPED COUNTRIES:
High Gross National ProductHigh per-capita GNP
STATS: 21% of global pop.Holds 85% of global wealthUse 88% of global resourcesGenerate 75% of global pollution
DEVELOPING COUNTRIES: Low Gross National ProductVery low per-capita GNP
STATS: 79% of global pop.Holds 15% of global wealthLittle industrialization
The two worlds
1 in 5 people live in luxury
3 in 5 people "get by"
1 in 5 people live in dire poverty
How is the distribution of wealth changing?
Trends in global wealth
Population x Affluence x Technology = Impact Number of
people
number of resource
“units” used per person
Environmental impactper resource
unit used
THE FORMULA: P x A x T = Environ. Impact
A differs in developed and developing countries
T by some technology (e.g., burning coal)T by some technology (e.g., solar power)
Calculating environ. impacts
P x A x T = Environ. Impact
Number of people
number of resource
“units” used per person
Env. impactper resource
unit usedEnv. impact
of population
=
=x
xx
x
Developed nations
Developing nations
Magnitude = width of circle
Figure 5.3
Where are populations increasing?
Figure 5.3c
Geography and growth
Figure 5.9Age structure diagrams
Growth rate = births - deaths
Growth increased by births or deaths
So which caused the recent increase in
population?
Rapid increases in population in 20th century
Population increases
Natural rate of increase
Birth rate-death rate
Both rates decline in 20th century
Rate of increase stable
Developed countries
Natural rate of increase
Death rates decline sharply
Birth rates do not follow
Rate of increase skyrockets
Developing countries
Why the drop in death rates?
Improvements in sanitation reduce incidence of disease
Industrialized agriculture gives higher yields, better nutrition
Antibiotics and better medicine reduce death rates
Figure 5.8
FACTORS THAT AFFECT FERTILITY RATES: Education and affluence
Urbanization
Cost of children
State pensions
Availability to birth control
Infant mortality
Women's age at marriage
Female education and employment
Importance of child labor
How will each of these factors affect birth rates?
What influences birth rates?
REPLACEMENT LEVEL FERTILITY: No. of kids per couple to replace themselves in the population
Developed = 2.1 and Developing = 2.6 in 1996
TOTAL FERTILITY RATE: Estimate of the no. of children a woman has in her lifetimeDeveloped = 1.6 and Developing = 3.4 in 1996Global average = 3.0 "Magic number" = 2.1
Measuring fertility rates
Figure 5.11
Figure 5.6
Get global TFR 2.1 for zero population growth (ZPG)THE GOAL:
METHODS:
Affluence and industrializationIncreased access to birth controlIncreased opportunities for womenEconomic incentives to reduce family size
Slowing population growth