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Environmental Science
Course Code
Carl Mitchell

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Chapter Six: Human Population
Most of population growth comes from poverty nations
oChina and India are worlds most populous nations
Although rate of global growth is slowing, we are still increasing in absolute
The human population is growing nearly as fast as ever:
Exponential growth is the increase in a quantity by a fixed percentage per
unit time
o(given percentage of a large number is a greater quantity THAN the
same percentage of a small number)
oTherefore, even if growth rate remains steady, population size will
increase by greater increments with each successive generation
Doubling time (70 / annual percentage growth rate)
Perspectives on human population have changed over time:
Thomas Malthus
oClaimed that unless population growth was limited by laws or other
social controls, the number of people would outgrow the available food
supply until starvation, war, or disease arose and reduced the
oHis work An Essay on the Principle of Population argued that a
growing population would eventually be checked either by limits on
births or increases in deaths
If limits on birth were not implemented soon enough, deaths
would increase

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oEngland favoured population growth as society industrialized but
Malthus argued that pressure of population growth on the availability
of resources could lead to disaster
Paul Ehrlich
oCalled a neo-Malthusian because like Malthus, he warned that
population growth would have disastrous effects on the environment
and human welfare
oHis book The Population Bomb, he predicted that rapidly increasing
human population would unleash widespread hunger and conflict that
would consume civilization by end of 20th century
oArgued that population is growing much faster than our ability to
produce food
oPopulation control is only way to prevent massive starvation,
environmental degradation
Is population growth really a problem today?
Worlds population growth made possible by technological innovations,
improved sanitation, better medical care, increased agricultural output, etc
oThese led to decline in death rates, drop in rates of infant mortality
Increase in crop yields and technology has brought down Malthusian and neo-
Malthusian predictions
Some cornucopian thinkers believe that resource depletion caused by
population increase is not a problem if new resources can be found to replace
depleted resources
Sheldon Richman
oBelieved that idea of carrying capacity does not apply to human world
because humans create the resources
oTruth is only few human resources are created by humans

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Population increases are a problem if they create stress on resources, social
systems, or natural environment leading to a decline in our quality of life
* Malthus, Ehrlich, and other neo-Malthusians predictions were NOT
* technological fix will come and rescue humans from problems brought by
population growth is NOT TRUE
Population is one of several factors that affect the environment:
IPAT model a formula that represents how humans total impact on the
environment results from the interaction among three factors: population,
affluence, technology
oMade by Paul Ehrlich and John Holdren
oI = P x A x T
oIncrease population impacts environment as more individuals take up
space, use natural resources, and generate waste
oIncreased affluence impacts environment through greater per capita
resource consumption that generally has accompanied enhanced
oChanges in technology may either decrease or increase human impact
on the environment
oI = P x A x T x S
oSensitivity (S) to denote how sensitive a given environment is to
human pressures
oVarious researchers have refined IPAT equation by adding terms for
the effects of social institutions (ex: education)
Impact boils down to either pollution or resource consumption
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