Sir

I was pleased to see Thomas Malthus commemorated in Roger Short's bicentennial essay1, but disappointed that agriculture's role in the population explosion was ignored.

The two “major factors” identified by Short (erosion of traditional breastfeeding practices, and conquest of infectious diseases) did surely contribute to the rapid growth of population, but only because they were accompanied by an increase in the food supply. The expansion of agricultural land since Malthus's time, and the enormous increases in crop yields resulting from the application of science to agricultural technology, were what allowed the population to grow to 6 billion. Yields per hectare of several major crops have increased by factors of two to seven in the United States in the past 60 years2, and in other countries by similarly large factors3.

Malthus's emphasis on food as the limit to population may be confirmed if agricultural productivity soon begins to level off, as many predict3.