0

2

4

6

8

10

1750 1800 1850 1900 1950 2000 2050 2100

Billions

Developed

Developing

World Population 1750-2100

Links between population andthe environment

1. Total pollution = (pollution per person 1. Total pollution = (pollution per person x population) x population) - pollution control - pollution control - assimilation - assimilation

2. Total resource use = (rate of resource use - recycling rate) x

population

As population increases...

1. Pollution will increase unless pollution control improves

2. Resources will be depletedunless recycling increases and resource use becomes more efficient

Thomas Malthus (1766-1834)

English demographer and economist

Graduated from Cambridge in 1788 (age 22)

Friend of Hume and Rousseau

Major work (published anonymously in 1798): An essay on the principal of population as it affects

the future improvement of society

NOT a short essay (600 pages long!)

Malthusian argument

1. Reproductive capacity of humans puts continual

pressure on the “means of subsistence”

2. Human numbers increase by geometric progression.

3. Subsistence resources increase arithmetically.

4. Land, unlike people, cannot breed.

The Malthusian principle

Time

Population,food

Checks on population

1. War

2. Seasons of sickness

3. Epidemics today AIDS

4. Pestilence

5. Plague

And the “ultimate” check:

6. Famine

What Malthus missed

1. Birth control and voluntary limits on population growth

(i.e. population growth less than geometric)

2. Agricultural productivity

(i.e. growth in food production greaterthan arithmetic)

The Malthusian principle, revisited

Time

Food

PopulationFood

Pop

A pattern of steadily increasing population growth, followed by aperiod of slowing population growth(as experienced by industrialized countries).

Generally indicated as an S-shaped curve for population through time.

Demographic transition

Frank Notestein (b. 1945)Three stages of population growth

1. High growth potential

2. Transitional growth

3. Incipient decline

1 2 3

1. High growth potential

Pre-industrialPre-industrial

Birth rate high (25-40/1000)

Death rate high

Life expectancy short

Population growth low but positive

Widespread poverty and misery

2. Transitional growth

Early industrialEarly industrial

Birth rate remains high or rises

Death rate low and falling

Life expectancy rises

Population growth “explosive”

Mortality declines before fertility dueto better health, nutrition, and sanitation

3. Incipient decline

IndustrialIndustrial

Birth rate drops due to desires to limit family size

Death rate low and stable

Life expectancy high

Population grows until birth rate = death rate

Characterized by higher levels of wealth and reduced need for large families for labor or insurance.

Message: Birth rates=death rates, country has completed the demographic transition

Message: Birth rates > death rates, country is still in stage 2 of the demographic transition

Key Points

1. Malthusian view of population growing faster than food supply has not come to pass.

2. Evidence in support of “demographictransition” is strong:

90% of Europe, 25% of Africa)

3. Neo-Malthusian views generally correspond toconcerns over environmental quality andspeed of demographic transition.

Message: Fertility rates respond to increases in per capita income, speeding the demographic transition