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3.1.1-.2 Human Pop Growth. Human population growth. This question is difficult to answer. Estimates are usually based on food, but human agriculture limits assumptions on available amounts. Human population growth rate has been growing more than exponentially. .

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This question is difficult to answer.

  • Estimates are usually based on food, but human agriculture limits assumptions on available amounts.

  • Human population growth rate has been growing more than exponentially.

What is the carrying capacity of Earth for humans?


1999

1975

domestication of plants, animals 9000 B.C. (about 11,000 years ago)

agriculturally based urban societies

beginning of industrial, scientific revolutions

HUMAN POPULATION GROWTH


Increase in growth rate

  • Expansion of habitat

  • Increased capacity in existing habitats

  • Substituting and importing resources

  • Population has sidestepped limiting factors:

    • Technology (agriculture)

    • Medicine

Increase in growth rate:


Population size has limits beyond which even humans can easily control

The availability of food and water

Invasion of parasites, pathogens, or disease

Over-crowding

Severe or sudden climatic changes

Pollution of air, soil and water

Population size has limits beyond which even humans can easily control:


If we do not take steps to control human population growth, it is likely that one or more of these growth-limitingfactors will eventually kick in to forcibly reduce our numbers.


Measuring population growth

Crude birth rate = the number of births per thousand individuals in a population per year.

Crude death rate = the number of deaths per thousand individuals in a population per year.

Fertility = the potential of reproduction exhibited in a population.

Measuring Population Growth


Developed Nations individuals in a population per year.

Developing Nations


Measuring population growth1

Natural increase rate = the form in which human population growth rates are usually expressed

Crude birth rate – crude death rate

10

Measuring population growth


Growth rate

4.5 growth rates are usually expressed

Developing

Countries

3.0

Population (billions)

Developed Countries

1.5

Projections

0

1950

1970

1990

2010

2030

Year

Human Population growth = 1.4% per year

Developing nations = 1.7%

Developed nations = 1.0%

Growth rate


Doubling time

Doubling time (T) = growth rates are usually expressed 70 .

annual percentage rate (g)

Doubling Time

Doubling time = the number of years it would take a population to double its size at its current growth rate.

Doubling time (T) = 70 . = 50 years

1.4


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