Lecture3_Population_and_Systems

Lecture3_Population_and_Systems - EAS 1600 Introduction to...

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Click to edit Master subtitle style EAS 1600 Introduction to Environmental Sciences Lecture 3 Population Change, Feedbacks, Equlibria We now begin our discussion of the first major topic- areas of the course: Population Growth and the Earth as a system
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Assimilated Satellite Image of City Lights
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Loss of Biodiversity
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Human population over time: Taken from Hidore, J.J., Global Environmental Change ,
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The figure on the preceding slide nicely illustrates the explosion that began towards the middle of the last millennium (probably due to rise in more modern agricultural practices) and really accelerated around the 1700's with the Industrial Revolution. A better sense of what happened is provided in the two following illustrations . ..
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Historic trends in human population ( total and urban) over past millenium. After Ness ( 1991) . Note that the rise in population with the Industrial Revolution is paralleled by a rise in urbanization.
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Theories of Human Population Growth Malthus, An Essay on the Principle of Population, 1798 Human population will increase in time geometrically (i,e., double in a fixed amount of time). Food supplies will increase linearly Eventually population will outstrip supplies and major famine will result
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Theories of Human Population Growth (cont’d) But Malthus’ theory was wrong : double rt double e t Pop t Pop t Pop ) ( ) ( 2 ) ( 0 0 = = Geometric (also called exponential) growth: rt e t Pop t Pop ) ( ) ( 0 = The time to double population, tdouble, is obtained by solving r r t double 693 . 0 ) 2 ln( = = r = rate of growth (or decay if negative)
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Theories of Human Population Growth In fact, population doubling time has decreased with time (i.e., population growth has been ‘super-exponential’) Question: What do you think caused these changes in doubling times? Date (AD) Population (Millions) t doubling Annnual Increase (%) 1 250 1650 0.04% 1650 500 200 0.35% 1850 1000 180 0.39% 1930 2000 46 1.51% 1976 4000 34 2.04% 2000 6000 49 1.40% Note that for this example in 1 AD r = 0.0004, in 1976 r = 0.0204 The annual increase is analogous to interest on your bank account
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This note was uploaded on 02/21/2011 for the course EAS 1600 taught by Professor Jimstjohn during the Fall '08 term at Georgia Institute of Technology.

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Lecture3_Population_and_Systems - EAS 1600 Introduction to...

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