When scholar and economist Thomas Malthus published his famous An Essay on the Principle of Population in 1798, in which he argued that war, famine and disease would keep population growth in check, the number of people on the planet was approaching one billion. But, as death at the hands of those once widespread miseries has fallen dramatically, the global population has surged. It took more than a century for the population to double to two billion in 1927, and it rose to three billion by 1960, four billion in 1974, and five billion in 1987. It then took just 12 years for the world population to shoot from five billion to six billion, and another 12 years to reach seven billion. The rapid rate of population growth has led to growing fears of a global population crisis.
What's the problem? Optimists hailed the birth of the seven billionth baby at the end of October as a cause for celebration, rather than concern. Thanks to advances in medicine, better access to healthcare and higher quality food, global life expectancy has risen from 48 years in 1950 to 68 years in 2011 as the infant mortality rate has also fallen significantly. But, say pessimists, with 15 million children still dying of hunger annually and human activity causing severe environmental damage, it's necessary to question whether the world can feed seven billion mouths, and whether the planet can sustain a human population predicted to hit nine billion by 2050.
According to the World Bank, food production must increase by 70 per cent by 2055 in order to keep pace with population growth. Although the past 40 years have already witnessed a threefold increase in farming productivity, there is little fertile land left to bring under the plough. And, with agricultural yields decreasing due to water shortages and climate change, maintaining a supply of food to meet demand could become a very real challenge. However, the concern that more people will cause more environmental damage is less serious. Population growth is concentrated in Africa and Asia, which have a smaller appetite for resources and make a far lesser contribution to environmental pollution than Europe and the US.
What's more, although the number of people on the planet is still rising, the rate of population growth is slowing down and the UN estimates that the eight billion milestone will take 14 years to reach, rather than 12 or less. Population growth peaked in the 1960s, when it was increasing at a rate of 2 per cent per year, but it has since halved. In addition, around 50 per cent of the world's inhabitants now live in countries where the fertility rate (that is the number of children a woman can expect to have) is below the replacement rate (the rate at which a population needs to multiply to sustain itself) of 2.1 births. Low fertility presents its own problems, such as high dependency ratio where a large generation of retired people rely on a smaller younger generation to support them.
Should overpopulation be considered a global threat? It is perhaps more apt to consider localised demographic challenges, and to concern ourselves not just with the size, but also the structure, of populations.