Thomas Malthus (1766–1834) was an English clergyman and political economist who introduced the so-called ‘Malthusian Problem’ in his Essay on the Principle of Population (1798). He summarized his central argument thus: ‘The power of population is indefinitely greater than the power in the earth to produce subsistence for man.’ His pessimistic conclusion was that population levels remain fairly constant in the long term because the planet is unable to sustain significant increases for more than short periods. In other words, economic stagnation will always rein in population growth. Although the global population has given the lie to his assumptions, his ideas continue to resonate with economists and, increasingly, environmentalists.
When Malthus wrote his treatise, he was swimming against the tide of opinion that held humanity was locked into a march of progress (see here). His central idea was that while population has a tendency to grow in rapid bursts, food production expands at a more constant rate as a result of the law of diminishing returns – there is a finite amount of land on which to grow food and increasing the labour supply results in increasingly smaller output gains. Therefore, Malthus contended, food shortages are inevitable since population growth outstrips growth in the food supply.
The resultant malnutrition leads, he said, to an increased death rate, accompanied by a dip in the birth rate as families regulate their reproduction in accordance to the food they have available to feed themselves. The population thus enters a period of ‘natural wastage’, resulting in more food being available to share around and a general spike in living conditions. But then the wheel turns again, since these improved conditions lead to fewer deaths and provide encouragement to have more children, raising the population level until lack of resources brings it back in line again. This ‘Malthusian trap’ – as it became known – goes hand in hand with a cycle of economic stagnation, in which the population makes do on just enough as they await the next inevitable wave of starvation, disease or other calamity that will bring the population back down to size. ‘To prevent the recurrence of misery is, alas! beyond the power of man,’ he declared.
Malthus offered no easy solution – even government welfare would only encourage an expansion of population size, hastening the onset of shortages, he suggested. However, he failed to take account of the technological advances (notably in agricultural production) that have propelled some 200 years of rapid global population growth, so that now we add about a billion people to the planet every decade. Nonetheless, his arguments have had profound influence on figures as diverse as Charles Darwin and John Maynard Keynes. Furthermore, as modern geographers, environmentalists and economists confront the idea that the planet might be nearing capacity – with battles for such basic resources as water becoming a genuine threat – there is a tide of opinion that Malthus may have had it about right all along.