Lecture 11 Human Population Growth

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Lecture 11 Human Population Growth

• Next Time Exponential Growth

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What is the biggest issue in wildlife ecology?

• Human population growth!
• Current Abundance
• World . 6 billion ... right now
• http//www.census.gov/main/www/popclock.html
• U.S. - 281,421,906 (2000 census?)
• U.S. - 135,000,000 (1940)

• Alaska - 626,932 (2000 census)
• Alaska - 550,043 (1990)
• Nevada - 1,998,257 (2000)
• Nevada - 1,201,883 (1990)

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How can we describe this change in population
size?

• ? finite rate of increase
• increase or decrease
• discrete - change per unit time (e.g., year)
• ? gt 1.0 increase
• ? lt 1.0 decrease
• ? 1.0 stable
• Nt No ?, where N abundance and t time

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How can we describe this change in population
size?

• r intrinsic (instantaneous) rate of increase
  (Malthusian parameter)
• Both ? and r express rates of change in birth,
  death,immigration, and emigration rate (BIDE)
• er ? or ln(?) r

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We can describe human population growth with
these parameters!

• U.S. population growth
• N1997/N1937 270,000/135,000 ? 2.00
• Change per year 1.012 1.2
  per year
• Actually rate has slowed some to 1 per year or ?
  1.01 or r 0.00995
• What is doubling time?
• Nt Noert
• 2No Noe rt double
• 2 ert double
• ln (2) rt double
• t ln (2) / r ln (2) / ln (?) ln (2) /
  0.0095 ln (2) / ln (1.01) 70 years
• Predicted U.S. pop in 2073 560 million

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What about the world?

• ? 1.015 or 1.5 per year
• Doubling time in 46 years
• 12 billion people in 2049