Human populations

Carrying capacity and the Malthusian model

Carrying capacity (K) is the maximum population that an environment can support for a long time without being degraded. For humans it depends not only on land and water but also on technology, trade and consumption levels.

Thomas Robert Malthus, in *An Essay on the Principle of Population* (1798), argued that:

• Population, if unchecked, grows geometrically (1, 2, 4, 8, 16…).
• Food supply grows only arithmetically (1, 2, 3, 4, 5…).
• So population will outrun food, unless checked.
• Positive checks raise the death rate: famine, disease, war.
• Preventive checks lower the birth rate: delayed marriage and “moral restraint”.

Critics of Malthus

• Technology: Malthus did not foresee big rises in food output, for example through the Green Revolution and better transport and storage.
• Ester Boserup argued the reverse: population pressure pushes farmers to invent better methods and to farm more intensively.
• Marx and others said poverty and hunger come from unequal distribution and ownership, not from too many people.
• The demographic transition showed that birth rates fall on their own as societies develop.
• Neo-Malthusians (such as Paul Ehrlich, *The Population Bomb*, 1968) revived his worries in the modern age.

Unequal resource consumption

Environmental impact depends on how much each person consumes, not just on numbers. The I = P × A × T equation (Impact = Population × Affluence × Technology) shows this. A person in a rich country typically uses many times more energy, materials and carbon than a person in a poor country. So a small, rich population can cause more damage than a large, poor one.

Anchored figures: the UN estimated that world population reached 8 billion on 15 November 2022. India’s Census 2011 counted about 121 crore people, and UN estimates showed India passing China as the most populous country in 2023.

Key points

• Malthus, 1798: population geometric, food arithmetic.
• Positive checks (famine, disease, war) vs preventive checks (late marriage, restraint).
• Boserup: population pressure leads to agricultural innovation.
• I = P × A × T.

Exam tips

Expect “geometric vs arithmetic” and “positive vs preventive check” questions. For critics, remember that Boserup turned Malthus around.

Common mistakes

• Swapping which grows geometrically (population) and which arithmetically (food).
• Calling famine a preventive check; it is a positive check.
• Thinking only population size matters for impact; consumption (A) and technology (T) also matter.