Thomas Malthus, at the end of the eighteenth century, argued that increasing population must inevitably lead to disaster. We were going to run out of food. Malthus was wrong, but that has not stopped generations of neo-Malthusians from claiming that it was going to be true next time. In the 1970s, The limits to growth claimed that the world was going to run out of energy. It isn’t. What happens in an economic market is that as an item grows scarce, it becomes more expensive. As some sources of energy will become more expensive, we will be forced to switch to other sources. There is no point at which the last drop of petrol will ever be poured into the last car, while other drivers look on in fury. This is just not the way that the economy works.
The other side of the Malthusian argument is about population. Population does not grow exponentially: the birth rate falls as the economy develops. The reasons are complex. Part of the explanation is the changing role of women, who delay childbearing when they have options for education and employment. Some reduction may be attributed to contraception; some, perhaps, to the effect of urbanisation on the costs of raising a child. But a significant element must be the fall that most countries have seen in infant mortality over the course of the last forty years. The association is clear and strong (try this link, which opens a new window): once parents see that children have a realistic chance of surviving to adulthood, the number of children they have drops markedly. As an Indian minister once commented, “The best contraceptive is development”.