By Clive Cookson
On October 31, earth will gain its seven billionth inhabitant, according to official UN population projections.
Of course, the data are not really accurate enough to predict the arrival of human number 7bn to the nearest day, or even year, but the symbolic moment has aroused an upsurge in the debate around ?overpopulation? that has ebbed and flowed since Thomas Malthus published his Essay on the Principle of Population in 1798.
Not since the ?population bomb? alarm of the 1960s and early 1970s – when there were half as many people on the planet as there are today – has the issue been so prominent in the public arena.
The tone of the discussion is generally less apocalyptic than it was 40 years ago, though the central concerns still revolve around the earth?s human ?carrying capacity?. How many people can live sustainably on this planet? Can we feed a global population that is growing by 76m per year and will exceed 9bn by 2050, according to median demographic estimates? And will the growing human burden on the earth eventually cause catastrophic and irreversible environmental damage, from climate change to mass extinction of wildlife?
Alas, scientists are nowhere near agreeing on an answer. ?Estimates of human carrying capacity range from a billion to a trillion people,? says Joel Cohen, head of the Laboratory of Populations at Rockefeller University, New York. ?Those numbers are really political numbers rather than scientific numbers, designed to support a particular viewpoint.?
However, Sir John Sulston of the University of Manchester, who is leading a study of global population for Britain?s Royal Society, says the target should not be to cram as many people as possible on to the planet. ?We have to look at what will allow humankind to flourish,? he says. ?We want to aim for a high quality of life and not just to scrape along.?
But not everyone sees over?population as a problem. The ?doomsters? are answered by ?boomsters? arguing that population growth can produce prosperity without environmental sacrifice.
Barring a global cataclysm, the number of people on earth will pass 8bn within the next 15 years or so. And doomsters and boomsters will still disagree over whether the planet is overpopulated.
? The Financial Times Limited 2011