3.1.1-.2 Human Pop Growth

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3.1.1-.2 Human Pop Growth
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Human population growth
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What is the carrying capacity of Earth for humans?

• 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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HUMAN POPULATION GROWTH
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Increase in growth rate

• Expansion of habitat
• Increased capacity in existing habitats
• Substituting and importing resources
• Population has sidestepped limiting factors
• Technology (agriculture)
• Medicine

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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

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

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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.

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Developed Nations
Developing Nations
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Measuring population growth

• Natural increase rate the form in which human
  population growth rates are usually expressed
• Crude birth rate crude death rate
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Growth rate

• Human Population growth 1.4 per year
• Developing nations 1.7
• Developed nations 1.0

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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
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• annual percentage rate (g)

Doubling time (T) 70 . 50 years

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