Malthus (1766-1834) produced his Essay on the Principle of Population in 1798. He said that the crux of the population problem was the existence of a tendency in mankind to increase, if unchecked, beyond the possibility of an adequate supply of food in a limited territory. Malthus thought that an increased food supply was achieved mainly by bringing more land into arable production.

He maintained that while the supply of food could at best only be increased by a constant amount in arithmetic progression, the human population tends to increase in geometric progression, multiplying itself by a constant amount each time. In time, population would outstrip food supply until a catastrophe occurred in the form of famine, disease or war, as human groups fought over increasingly scarce resources.

In a later paper Malthus placed significant emphasis on moral restraint as an important factor in controlling population. Clearly Malthus was influenced by events in and before the eighteenth century and could not have foreseen the great advances of the following two centuries that allowed population to grow at an unprecedented rate alongside a huge rise in the use of resources. Many advances in agriculture since his time, such as artificial fertilisers and pesticides, new irrigation techniques, high-yielding crop varieties, cross-breeding of cattle, greenhouse farming and land reclamation, have contributed to huge increases in agricultural production.