In stage 2 of the demographic transition, populations grow fast. Can food keep up? This question has been argued for more than two centuries, and it is still debated. Your job is to know each side's argument, not to pick a winner.
Key idea
In An Essay on the Principle of Population (1798), Thomas Malthus argued that population tends to grow faster than the food supply, so hunger, disease and war (or later marriage and fewer births) would hold numbers down. Critics point to food output that has grown faster than population and to falling birth rates. Neo-Malthusians warn that limits on water, land, energy and the environment still matter.
Why it works
Malthus said population could grow geometrically (1, 2, 4, 8, …) while food could grow only arithmetically (1, 2, 3, 4, …). If that were true, population would always outrun food. So far, farm output has kept ahead: new crop varieties, fertilizer, irrigation and machines raised yields, and birth rates fell in most countries. The Danish economist Ester Boserup (1965) argued that growing populations push farmers to farm more intensively. Neo-Malthusians, such as the biologist Paul Ehrlich in The Population Bomb (1968), answered that today's gains may use up soil, water and fossil fuels faster than they can be replaced.
| Position | Main argument | Evidence they point to |
|---|---|---|
| Malthus (1798) | Population outruns food | Famines and food shortages in history |
| Critics (Boserup and others) | People invent ways to grow more food; birth rates fall | World food output has grown faster than population |
| Neo-Malthusians | Limits are environmental, not just food | Groundwater use, soil loss, pressure on land and energy |
A worked example
Worked example: Growth by multiplying and by adding
Start at 1. Population doubles each period; food adds 1 each period. Compare after 4 periods.
- Population: 1, 2, 4, 8, 16.
- Food: 1, 2, 3, 4, 5.
- After 4 periods population is 16 and food is 5.
Answer: Population 16, food 5: by Malthus's assumptions, population soon outruns food.
Common mistake
Students treat Malthus as either proven right or simply wrong. His prediction of permanent mass famine has not come true for the world as a whole, because food output grew faster than he expected. But scholars still debate whether limits on water, land and the environment will matter in the future. On an exam, give each side's argument and its evidence.