Population and Thomas Malthus
10/21/2012 7:51:00 PM
How are populations of given species affected by changing environmental
Example: predator/prey model (hare/lynx)
o As population of prey (hare) increases, the population of predator (lynx) also
o Then as the population of the predator (lynx) increases, the population of the
prey (hare) will decrease, which, in turn will cause the lynx population to
“Feedback mechanism” – forces which result in equilibrium conditions, I.e., numbers
of both predators and prey in keeping with the capacity of the environment.
Question: how do human populations respond to changes in environmental and
o 1. Increase food supply
o 2. Stabilize/decrease populations
o 3. ???
2. Thomas Malthus: “An Essay on the Principles of Population”, 1798
1789 “An Essay on the Principle of Population”
Malthus (1766-1834) – clergyman, professor of history and political economy
World population almost 1 billion in 1798
Basic ideas underlying Malthus’ argument:
o (i) Food supply increases in a linear (arithmetic) fashion (1,2,3,4,5…)
o (ii) Population increases in a geometric exponential fashion (1,2,4,16,256,…)
As a result of these assumptions, population growth will ultimately create stress on
the means of subsistence, i.e., population will exceed the carrying capacity of the
environment, resulting in war, vice, and misery (Malthus called these “natural
checks”) that would limit further population increases.
Was Malthus correct?
(i) He could not have foreseen significant increases in food production n 19th and 20th
centuries, i.e., food supply increase was not linear (as he assumed)
(ii) Perhaps (?) the present slowing of population increase is a response to the Earth’s
carrying capacity being reached.
Influence of Malthus – “Neo-Malthusians” such as Paul Erlich (“The Population
Bomb”, 1968) and The Club of Rome (“Limits to Growth”, 1972)