Basic concepts and human history

Human Population

Growth

Human population has recently exploded in size

Note 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-firedReplaces water power

Factories need not be near waterPowers 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 improved

Root crops popularized

Late 1800's inorganic fertilizer produced

Mechanized farming and processing

Industrial revolution

SOCIAL CONSEQUENCES:

Urbanization of population

Plentiful food

Medicine and sanitation reduce mortality

END RESULT: Populations rise rapidly

Mass production improves quality of life

Industrial revolution

Num

bers

of

hum

an

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

Nu

mb

er

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 off

Population 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 worlds

DEVELOPED COUNTRIES:

High Gross National Product

High per-capita GNP

STATS:

21% of global pop.

Holds 85% of global wealth

Use 88% of global resources

Generate 75% of global pollution

DEVELOPING COUNTRIES:

Low Gross National Product

Very low per-capita GNP

STATS:

79% of global pop.

Holds 15% of global wealth

Little 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 used

Env. impactof 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 lifetime

Developed = 1.6 and Developing = 3.4 in 1996

Global 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 industrialization

Increased access to birth control

Increased opportunities for women

Economic incentives to reduce family size

Slowing population growth