1.0       INTRODUCTION:  

Any treatise on population ethics must have an appropriate moral discourse of the concept of population. To this end, this chapter would look at the concept of population and its relationship with the environment in the moral and non-moral senses as it affectshuman and non-human resources. It would also examine or consider the moral implications of population control.For the most part, this chapter would look like an essay on social science; however a proper analysis of population is necessary for the rigorous philosophical discourse which follows.


            Population studies are usually concerned with the quantitative aspect of it.That is, the size, structure, characteristics and territorial distribution of human populations and the changes occurring in them. It is also concerned with the study of the underlying causes of population phenomena.

According to English lexicography, population is the total number of people living in a particular geographical area. In a more general sense, population is a summation of all the organisms of the same group or species, which live in the same geographical area, and have the capability of interbreeding.[i]Human population is of primary concern here, although its effects and relations with non-human populations areof equal importance. Demography, derived from the Greek word “Demos” meaning “people”, is the scientific study of population. It is concerned with the study of the components of population, population variations, and changes. It looks at the evolution of population overtime, and also tries to scientifically predict future evolutions in population changes.


The study of population cannot be done in isolation. When one attempts to describe, compare or explain the determinants of population phenomena, social phenomena has to be taken into consideration. To this end, the study of population is multidisciplinary in nature, involving an understanding of biology, genetics, mathematics, statistics, economics, etc.Moreover from this, the subject matter of any exposition on population would include an understanding of migration, social mobility, fertility, and mortality. The primary source of population data is population census which is the collection of information about people living in a particular geographical area at a certain time. Other sources of population data include vital statistics, dual report system, sample survey, population registers, etc. In what follows, I shall briefly comment on some aspects of population dynamics.

1.2.0    MIGRATION

            Migration is one of the important factors of population change. It affects a population size socially, culturally, economically and politically. According to The UN Demographic Dictionary, Migration is a form of geographical mobility or spatial mobility between one geographical area to another, generally involving a change in residence from the place of origin or place of departure to the place of destination or the place of arrival.[ii] It is distinguished from other forms of movements in that it tends to be more permanent.

Migration may increase or decrease the size and structure of a population depending on the form of migration taking place. Immigration refers to the movements into and emigration refers to the movements out of a population territory. Thus, migrants leaving Nigeria to India to settle are immigrants to India, and emigrants to Nigeria.

1.2.1    MORTALITY

            Mortality also plays an important role in population dynamics. It is basically the study of the effects of deaths on the population. Since death can only occur after birth, mortality is the study of the span between birth and death of the population. As it would be pointed out in the theories of population, the factor of mortality plays a dominant role in the decrease in population rate. The study of mortality is useful in the analysis of demographic conditions. It helps to determine the possible changes in mortality conditions for the future.

1.2.2    FERTILITY

            Arguably, human fertility is primarily responsible for the biological replacement and maintenance of human society. The growth or sustenance of human population depends largely on the factor of fertility. It is a sort of positive force through which the population expands. The term fertility is generally used to indicate the actual reproductive performance of a woman or group of women and it starts with adulthood. Thus, the beginning of puberty is an indication of fertility. Fertility is the actual reproductive performance of an individual or group.[iii]


            When the population of a given geographical area is much more than the available resources obtainable from such an area, such a place is over-populated. This usually leads to an overload on the workload of the environment, and in extension a reduction in the quality of life for the populace.Over-population arguably occurs in developing or under-developed communities where there is a high level of poverty and a low level of education concerning the relationship between the environment and the populace.


            Under-population is a situation where the population of a given geographical area is much lower than the available resources. In the case of under-population, there is usually wastage of environmental resources due to lack of human resources to properly harness them. Under-population equally results in a less than desirable quality of life, and many people are left impoverished due to the lack of certain basic needs that would otherwise have been available if there were more people to add to the available human resources.


            When the available resources in a given area are proportional to the population size, the result is optimum population. Here, proportionality indicates a sort of equilibrium between human resources and non-human resources. In this case, the available resources in such a geographical area are properly harnessed to their best levels, and in turn this creates a living condition that is best suited to both the environment and the human population on it. Amongst the three theories above, optimum population is the preferred population. Precisely, given that in a state of optimum population, the development of a nation can progress at all levels with optimal moral results. More of this would be considered fully in the discussion of classical population theories.


            There is a two way relationship between the population and the environment. First, the environment plays a vital role in human sustenance. As has been shown in chapter one, the environment is fundamental to human existence, for the simple reason that the material basis for the reproduction of life – of the various forms of life – derives from the environment. It is from the environment that the populace extracts resources necessary for its survival. The development and the wellbeing of human beings cannot take place without regard to the right to life, the natural capital called land, natural resources and the environment in which life itself must flourish.[iv] Thus, the importance of the environment to the population cannot be overstressed. Simply speaking, without a viable environment, there would be no human population to be concerned about.

            On the other hand, the population rate also goes a long way in affecting the viability or otherwise of the environment.As part of the environment when taken holistically, humans have a major influence on their environment. Some human actions have helped in protecting species and ecosystems while others have resulted in adverse effects on the non-human environment. When the population is high, the use of environmental resources would be high as well, and this would result in the problem of maintaining the population in the face of the limited supply of non-renewable environmental resources. This may lead to a lot of environmental problems – pollution, degradation of soil and water, present-day ozone layer desecration, etc. – which would spell doom for the environment as we know it. This impresses upon us the need to consider the environmental problem as one which requires an urgent solution.



            Thomas Malthus is arguably the first economist to declare a methodical doctrine of population. Although not the first man to make the observations he made, the work of Malthus had the greatest influence on the major classical economists that followed him.[v]His book AnEssay on the Principle of Population, was originally written as a response to two essays – An Inquiry into Political Justice (1793) by William Godwin, and Sketch for a Historical Picture of the Progress of Human Mind (1795) by Marie Jean Nicolas Caritat, the Marquis de Condorcet – that advanced the notion of the eventual perfection of society, which Malthus found to be overly optimistic.

            Malthus starts by asserting two basic propositions; first, that food is necessary to the existence of man, and secondly, that the passion between the sexes is necessary and will remain nearly in its present state. These two propositions he claims, are fixed laws of nature:

“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 are now…”[vi]

            Having asserted these two propositions, and established that it would be unphilosophical to infer that they would cease to be what they are – fixed laws of nature – Malthus goes ahead to assert that “the power of population is indefinitely greater than the power in the earth to produce subsistence for man.”[vii]Thisleads us to the main thesis in the Malthusian population theory; the dependence of population growth on the material conditions of the economy. For Malthus, human capacity to reproduce would surpass the earth’s physical capacity to produce.[viii] In order to have a clear understanding of Malthus’ principle, it is necessary to look closely at the logic underlying his argument. He states that population growthwhen unchecked, increases ‘geometrically’ or exponentially and that subsistence for man on the other hand increases ‘arithmetically’. Thus, population increases along the order of 1, 2, 4, 8, 16, 32…, whereas subsistence increases much slower at the rate of 1, 2, 3, 4… For Malthus, this disharmony in the growth rate of both factors would lead to one result: widespread poverty and starvation, which would only be checked by natural occurrences such as disease, high infant mortality, famine, war or moral restraint.

According to Malthus’ theory, there are two steps to controlling population; preventative and positive checks. The preventative checks includes measures such as control of birth rate, late marriage, celibacy, ethical moderation, etc. These checks arise from man’s reasoning capability which could enable him/her to foresee the consequences of certain actions. These checks do not discriminate, and seem to operate in some degree through all ranks of the society. The positive checks to control population on the other hand seem to affect largely the non-elite members of the population. These checks include famine, misery, plague, war, etc. According to Malthus, the positive checks are necessary as the preventative checks would largely fail in the job of reducing the numbers of the poor. If the positive checks are unsuccessful, then inevitably, famine would be the resulting way of keeping the population down. THE MORAL IMPLICATIONS OF THE MALTHUSIAN THEORY

The Malthusian theory of population is a highly pragmatic one. As has been shown by the extensive use of preventive measures like late marriages, birth control and various other contraceptives, the significance of the Malthusian Law cannot be over emphasized.However, the checks it recommends as means to avoid tipping the Malthusian equilibrium raises many fundamental ethical concerns. First, the positive checks to control population are methods that would fail any moral test when carried out intentionally. Thus, the positive checks are morally inadequate as means of controlling population. The preventative checks are not clear of moral hurdles either. While the use of contraceptives and the like have become widely accepted in present da global world, there are still many ethical concerns that comes up. There is the case of the morality of abortion, although it remains debatable whether the use of contraceptives entails abortion. Regardless, the control of birth rates impinges on the basic liberties of individuals to freely procreate. These ethical concerns would be discussed in detail in chapter three. Malthus’ thesis however, remains applicable to many countries of the world today, and Walker was not far off the mark when he wrote “The Malthusian Theory is applicable to all communities without any consideration of colour and place.”[ix]


            Unlike the Malthusian theory, the optimum theory of population does not seek to establish a relationship between population growth and food supply. Rather, it is concerned with the relations between the size of population and production wealth.According to Zimmerman, there is no true “father” of the doctrine of optimum population. Arguably propounded by Edwin Cannan in his book Wealth published in 1924, the optimum population theory is also associated with Knut Wicksell and can be traced to works of Plato and Aristotle.[x]

            Various definitions of optimum population can be found in literature, and the word “optimum” is usually used in such contexts to represent “best”. Thus, when one seeks “optimum population”, one seeks the best possible number of people geared towards achieving a given index. When such an index, which is conditioned by population, is at maximum, one has attained optimum population. Thus, population sizes are said to be optimal depending on what factors are being maximized: income or consumption per capita, total income or consumption, life expectancy and military potential, etc. In most cases, per capita income or output is the factor being maximized. Cannan discussed optimum population in relation to the returns to industry as a result of human labour on land:

“The truth is that the productiveness of industry is sometimes promoted by an increase of population and sometimes by a decrease of population… At any given time the amount of labour which van be exerted on a given extent of land, consistent with the attainment of the greatest productiveness of industry possible at that time, is definite… An increase of population is often one of the most essential requisites for increasing the productiveness of industry.”[xi]

            Cannan introduced much later, the dynamic aspect of the theory, in his subsequent work:

“We have to treat the ideal or optimum in regard to population as being the right movement (i.e. increase or decrease) of population rather than define it in reference to one particular point of time. The right movement is that which will give the largest returns to the industry in the long run, the interests of the people of all the generations being taken into account.”[xii]

            The extracts above indicate that certain basic postulations underlie the general thesis of the optimum theory of population. First, there is the belief that the resources of a country are given at certain points in time but generally vary overtime, while there is little or no change in the production techniques being employed. There is also the belief that the stock of capital remains the same (land, in the case of the above).Based on these postulations, the optimum populace is that ultimate size of population which affords the utmost income per head. All things being equal, any divergence from this optimum sized populace will result in a drop in the per capita income. When it is a decrease in population size, an increase in the populace is required to re-attain the optimum population status, and alternatively in a case of a rise in population, a decline is required to enable the per capita income to be maximized again.

[i] Oxford Advanced Learners Dictionary, International Students Edition, 7th Edition. Oxford University Press, 2005.

[ii] United Nations, Multilingual Demographic Dictionary, op. cit., p.46

[iii] Glossary of demographic terms, Population Reference Bureau. Retrieved from 

[iv] Ikpeze, G. N., “The Environment, Oil, and Human Rights in Nigeria”, in The Legislative and Institutional Framework of Environmental Protection in the Oil and Gas Sector. p.1

[v] Before Malthus, see Botero (1589), and Adam Smith (1776). The influence of Malthus may first be noticed in the works of Ricardo and John Stuart Mill and his propositions remain on the development of modern population and growth theory.

[vi] Malthus, T. (1798). “An Essay on the Principles of Population”. London (1798). Electronic copy published by Electronic Scholarly Publishing Project, (1998). Sourced from 

[vii]Malthus, T., (1798). p. 4

[viii] Currais, L., “From the Malthusian Regime to the Demographic Transition: Contemporary Research and Beyond”, in Junho (ed.) Economica, Vol. II, No. 3, (2000). pp. 75-101. (p. 77)

[ix]Mondal, P. 2016. sourced from 

[x] Zimmerman, K. F. (1989). “Optimum Population: An Introduction”, in K. F. Zimmerman (Ed.), Economic Theory of Optimal Population, Springer-Verlag. Berlin et al., pp 1-16. p. 3

[xi] Cannan, E. (1903) Elementary Political Economy, London: P.S. King & Staples Limited. (Originally published in 1888). pp. 22-23

[xii] Cannan, E. (1928) Wealth. London: P.S. King & Staples Limited. pp. 61



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