A theory of human population growth has been proposed by T. R. Malthus (1778). According to this, when unrestricted, the human population grows geometrically (i.e., 2 to 4 to 8 to 16 to 32 and so on) whereas the means of its subsistence (food etc.) grow only arithmetically (i.e., 2 to 4 to 6 to 8 to 10 and so on). This leads to insufficiency of the means of subsistence for an exponentially growing population. It causes a large number of problems to a nation as well as to an individual family and society. So there could be happen some adverse effects of overpopulation. Mainly six types of adverse effects are as follows:
i) Unemployment and poverty
ii) Shortage of food, shelter and clothing
iii) Low level of education and literacy
iv) Unhealthy hygienic conditions
v) Pressure on environment and pollution
vi) Social problems
Effects of overpopulation: Unemployment and poverty
Overpopulation leads to increase in unemploy¬ment and poverty as the facilities of employment are not increasing significantly. Advancement of technology reduces the need of manual work and thus scope of employment. So, workers get less salary and the per capita income is low. About maximum of the under developing country populations are living below the poverty line.
Effects of overpopulation: Shortage of food, shelter and clothing
Poor countries overburdened with population face an acute shortage of food, housing facilities and clothing. In many developing and under developing country, at least one fifth of the populations are undernourished or malnourished. Many people are homeless and live under the open sky with insufficient clothing.
Effects of overpopulation: Low level of education and literacy
Education is a basic human right and is necessary for economic and social development of a country. We know that, a person is said to be literate if he or she can read and write with understanding at least in any language. In overpopulated countries, large numbers of people are remaining uneducated and even illiterate. Poor people usually do not want to send their children to schools and prefer to engage them in earning money by any means by using them as child labor. As a result of this, the rate of early drop out from the school is also very high.
Effects of overpopulation: Unhealthy hygienic conditions
To provide proper health services to every citizen is not possible for the overpopulated countries. Hospitals and health centers are usually insufficient and thus overcrowded with patients, who do not get proper medical treatment. In such countries, many people live in slums having unhygienic conditions. The children of such people are deprived of love and proper care. So, in spite of the health care programs taken by the government, the child mortality rate is remaining high.
Effects of overpopulation: Pressure on environment and pollution
Population explosion imparts a heavy pressure on the limited natural resources that are used up day by day. Overpopulation is associated with intensive urbanization, deforestation, use of fertilizers and pesticides for better agriculture, use of fossil fuels as source of energy and production of wastes. All these show the way to pollution of environment, which is tremendously hazardous for mankind.
Effects of overpopulation: Social problems
Overpopulation has led to a social imbalance between the developed and developing countries. The per capita use of resources in a developed country is many times greater than that in a developing country. This has led to aggressive natural resource gaining, colonialisation and war. Excessive growth of population increases the incidence of crimes in a society and creates various problems for the society.