Malthusian catastrophe

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A Malthusian catastrophe, sometimes known as a Malthusian check, Malthusian crisis, Malthusian dilemma, Malthusian disaster or Malthusian trap, is a return to subsistence-level conditions as a result of agricultural (or, in later formulations, economic) production being eventually outstripped by growth in population. Theories of Malthusian catastrophe are very similar to the subsistence theory of wages. The main difference is that the Malthusian theories predict over several generations or centuries whereas the subsistence theory of wages predicts over years and decades.

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Traditional views

In 1798 Thomas Malthus published his now famous An Essay on the Principle of Population, describing his theory of quantitative development of human populations:

I think I may fairly make two postulata. First, That food is necessary to the existence of man. Secondly, That the passion between the sexes is necessary and will remain nearly in its present state. These two laws, ever since we have had any knowledge of mankind, appear to have been fixed laws of our nature, and, as we have not hitherto seen any alteration in them, we have no right to conclude that they will ever cease to be what they now are, without an immediate act of power in that Being who first arranged the system of the universe, and for the advantage of his creatures, still executes, according to fixed laws, all its various operations.
[...]
Assuming then my postulata as granted, I say, that the power of population is indefinitely greater than the power in the earth to produce subsistence for man. Population, when unchecked, increases in a geometrical ratio. (Malthus 1798, Chapter 1, online [1])

Series increasing in geometric progression are defined by the fact that the quotient of any two successive members of the sequence is a constant (e.g. a populations has an average birth rate of, say 1.2, or in the Malthusian' world of the 18th century, maybe rather 2.3 babies per population member in 50 years: so the entire unchecked population will grow in a ratio of 1.2 or 2.3 per 50 years). Malthus assumed the growth of agrarian economics to be linear (the arithmetic ratio is defined so that any two successive members of the sequence have a constant difference).

If unchecked, progressive growth can easily outrun linear growth, even if the quotient between successive sequence members is only slightly larger than 1.0. So Malthus concluded that the population will be naturally checked by misery, vice or the like in natural development. Every phase of unchecked exponential progression (possible e.g. when inhabiting new habitats or colonies, e.g. on the American continent at Malthus' time, or when recovering from wars and epidemic plagues) will be followed by a catastrophe or misery, and thus unlimited growth may even directly cause misery and vice (Malthus 1798, chapter 7: "A probable cause of epidemics", online [2]).


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Neo-Malthusian theory

Neo-Malthusian theory argues that unless at or below subsistence level, a population's fertility will tend to move upwards. Assume for example that a country has 10 breeding groups. Over time this country's fertility will approach that of its fastest growing group in the same way that

<math>f(t) = a\times1.01^t + b\times1.02^t, \mbox{where}~b \ne 0</math>

will eventually come to resemble

<math>g(t) = b\times1.02^t</math>

regardless of how large the constant a is or how small the constant b is. Under subsistence conditions the fastest growing group is likely to be that group progressing most rapidly in agricultural technology. However, in above-subsistence conditions the fastest growing group is likely to be the one with the highest fertility. Therefore the fertility of the country will approach that of its most fertile group. This, however, is only part of the problem.

In any group some individuals will be more pro-fertility in their beliefs and practices than others. According to neo-Malthusian theory, these pro-fertility individuals will not only have more children, but also pass their pro-fertility on to their children, meaning a constant selection for pro-fertility similar to the constant evolutionary selection for fertility genes (except much faster because of greater diversity). According to neo-Malthusians, this increase in fertility will lead to hyperexponential population growth that will eventually outstrip growth in economic production. This appears to make any sort of voluntary fertility control futile, in the long run. Neo-Malthusians argue that although adult immigrants (who, at the very least, arrive with human capital) contribute to economic production, there is little or no increase in economic production from increased natural growth and fertility. Neo-Malthusians argue that hyperexponential population growth has begun or will begin soon in developed countries.

To this can be added that, unknown to Malthus, farmland deteriorates with use. Some areas where there was intensive agriculture in classic times had already declined in population because their farmland was worn out, long before he wrote.

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Non-occurrence of the catastrophe

At the time Malthus wrote, most societies had populations at or near their agricultural limits. But by the late 20th century, the new agricultural technologies of the green revolution had greatly expanded agricultural production throughout the world (exponential not arithmetic growth rate as Malthus believed, for food production), and that what he termed 'misery' war, political unrest, and other forms of population control would lower population far before the famine he believed would occur.

Of Malthus's 'misery and vice', the most powerful factors were population control that many do not deem to be miserable or sinful, despite Thomas Malthus's opinions. Most technologically developed countries had by this time passed through the demographic transition, a complex social development in which total fertility rates drop drastically in response to lower infant mortality, more education of women, increased urbanization, and a wider availability of effective birth control. By the end of the 20th century, these countries could avoid population declines only by permitting large-scale immigration. On the assumption that the demographic transition would spread to less developed countries, the United Nations Population Fund estimated that human population would peak in the late 21st century rather than continue to grow until it exhausted available resources.

Another problem is that there is no strong evidence that the human population—nor any real population—actually follows exponential growth. In plant or animal populations that are claimed to show exponential growth, closer examination invariably shows that the supposedly exponential curve is actually the lower limb of a logistic curve, or a section of a Lotka-Volterra cycle. Also, examination of records of estimated total world human population ([3] [4]) shows at best very weak evidence of exponential growth: Image:Extrapolated world population history.png

The annual increase graph does not appear as one would expect for exponential growth. For exponential growth, it should itself be an upward trending exponential curve whereas it has actually been trending downward since 1986. Also the rate of increase should increase, whereas, of the increase between the early 1950s and today, five-sixths occurred in the 1950s and the first half of the 1960s (presumably attributable to the Green revolution); it then rose to a peak in 1989 and has since declined to levels approaching those of 1970.

Image:World population increase history.png

Though short-term trends, even on the scale of decades or centuries, do not necessarily disprove the underlying mechanisms promoting a Malthusian catastrophe over longer periods, the relative prosperity of the human population at the beginning of the 21st century, and the apparent failure of spectacular predictions of mass starvation or ecological collapse made by activists such as Paul R. Ehrlich in the 1960s and 1970s, has led many people, such as economist Julian L. Simon, to question its inevitability.

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Application to energy/resource consumptions

Another way of applying the Malthusian theory is to substitute other resources, such as sources of energy for food and resource /energy consumption for population. (Since modern food production is energy and resource intensive, this is not a big jump. Most of the criteria for applying the theory are still satisfied.) Since resources / energy consumption is increasing much faster than population and most of our resources / energy comes from polluting and non-renewable sources, the catastrophe appears more imminent, though perhaps not as certain, than when considering food and population continue to behave in a manner contradicting Malthus's assumptions.

Retired physics professor Albert Bartlett, a modern-day Malthusian, has lectured on "Arithmetic, Population and Energy" over 1,500 times. He published an article entitled Thoughts on Long-Term Energy Supplies: Scientists and the Silent Lie in Physics Today (July 2004).

For a response to Bartlett's argument, see two articles on energy and population in Physics Today, November 2004 [5], and following letters to the editor.

The most alarming aspect of this is pollution, as it appears possible that during the period when world population is declining due to shortages and crowding, pollution may be ignored by desperate, starving people to the point where the Earth becomes uninhabitable.

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See also

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External links

es:Catástrofe maltusiana fr:Catastrophe malthusienne nl:Malthusiaanse catastrofe sk:Maltuzianizmus

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