Malthusian Theory of Population Growth: Definition & Overview

Known for his work on population growth, Thomas Robert Malthus argued that if left unchecked, a population will outgrow its resources, leading to a host of problems. In this lesson, we will define and discuss the Malthusian theory of population growth.
Malthus on Population Growth
Can you picture a billion people? It’s difficult, isn’t it? Now, multiply that by seven, and we’re approaching the world’s population. In 2012, we exceeded seven billion people and are predicted to reach 9.6 billion by the year 2050. All of these extra people need food, water, space, and energy to survive.

This unprecedented growth has put a strain on our environment, economies, governments, infrastructures, and social institutions. While growth in developed nations has slowed down in recent years, overcrowding has been a worldwide concern for centuries. One of the first to publicly address the limits of the earth and the dangers of population growth was Thomas Robert Malthus (who lived from 1766-1834), an English scholar and cleric.

Thomas Robert Malthus
Thomas Robert Malthus
The Malthusian Theory
Malthus’s early writings were pamphlets that addressed economic and political issues of his time. In opposition to the popular 18th century European view that society was constantly improving, he wrote about the dangers of excessive population growth.

In his 1798 work, An Essay on the Principle of Population, Malthus examined the relationship between population growth and resources. From this, he developed the Malthusian theory of population growth in which he wrote that population growth occurs exponentially, so it increases according to birth rate.

For example, if every member of a family tree reproduces, the tree will continue to grow with each generation. On the other hand, food production increases arithmetically, so it only increases at given points in time. Malthus wrote that, left unchecked, populations can outgrow their resources.

According to Malthus, there are two types of ‘checks’ that can reduce a population’s growth rate. Preventive checks are voluntary actions people can take to avoid contributing to the population. Because of his religious beliefs, he supported a concept he called moral restraint, in which people resist the urge to marry and reproduce until they are capable of supporting a family. This often means waiting until a later age to marry. He also wrote that there are ‘immoral’ ways to check a population, such as vices, adultery, prostitution, and birth control. Due to his beliefs, he favored moral restraint and didn’t support the latter practices.

Positive checks to population growth are things that may shorten the average lifespan, such as disease, warfare, famine, and poor living and working environments. According to Malthus, eventually these positive checks would result in a Malthusian catastrophe (also sometimes called a Malthusian crisis), which is a forced return of a population to basic survival.

The Irish potato famine of the 19th century has been considered a classic example of a Malthusian catastrophe. In addition to dealing with political and economic relations with England and fragmentation of their land, the rapidly growing Irish population was running out of food.

There are often other factors involved in events that could be labeled as Malthusian catastrophes, so many scholars take caution when providing modern examples.

A graph illustrating the Malthusian theory of population growth
Malthusian Theory of Population

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