Ch. 4 The Human Population and the Environment

• Age structure• Birth rate• Death rate• Demographic transition• Growth rate• Human carrying capacity• Life expectancy• Logistic carrying capacity• Logistic growth curve• Maximum lifetime• Population• Population dynamics• Species• Zero population growth

Age Structure Diagrams

Growth Rate

• Births – deaths = r Total population

20,000 births – 15, 000 deaths = .01(x100) = 1.0%

500, 000 people

Average crude birth rate Average crude death rate

World

All developedcountries

All developingcountries

Developingcountries

(w/o China)

21

9

11

10

24

8

27

9

© 2004 Brooks/Cole – Thomson Learning

Human carrying capacity

Carrying capacity

Carrying capacity of Earth

How to determine human carrying capacity of Earth

• 1. extrapolate from past growth – logistic growth curve

• 2. packing problem approach• Deep ecology

Life expectancy

Demographic Transition Model

Demographic Transition• Preindustrial stage: little population growth.

Living conditions are harsh. High birth and high death rate.

• Transitional stage: start of industrialization, higher food production, health care. Population booms

• Industrial stage: industry, medical care, etc now well established. Population growth slows. Most developed countries in this stage.

• Postindustrial stage: birth rate declines, population stable, then slowly decreases.

A Closer Look 4.1 – Growth of Human Population

• Stage 1 – Hunters and Gatherers• Stage 2 – Preindustrial, Agriculture• Stage 3 – The Machine Age• Stage 4 – The Modern Era

Logistic Growth Curve

• Assumes: a constant environment a constant carrying capacity a homogenous population- Fig. 4.4 – inflection point- Used to forecast human population growth

Population and Technology• T = P x I or I = PAT• Total Impact = Population x Average Environmental Impact

per person• The average rich-nation citizen used 7.4 kilowatts (kW) of

energy in 1990—a continuous flow of energy equivalent to that powering 74 100-watt lightbulbs. The average citizen of a poor nation, by contrast, used only 1 kW. There were 1.2 billion people in the rich nations, so their total environmental impact, as measured by energy use, was 1.2 billion x 7.4 kW, or 8.9 terawatts (TW)—8.9 trillion watts. Some 4.1 billion people lived in poor nations in 1990, hence their total impact (at 1 kW a head) was 4.1 TW

Limiting Factors

• Categories – short-term, intermediate-term, and long-term

• Dispersal of certain pollutants, such as toxic metals, into water and fisheries - ?

• Soil erosion - ?• Disruption of food distribution in a country

caused by drought for instance -?

Zero Population Growth

• http://www.pbs.org/wgbh/nova/earth/population-campaign.html