This is a column I don't want to write. Its subject is ugly; it makes me instinctively recoil. I have chastised people who bring it up at environmentalist meetings. The people who talk about it obsessively have often been callous about human life, and consistently proved wrong throughout history. And yet... there is a grain of insight in what they say.

The subject is overpopulation. Is our planet over-stuffed with human beings? Are we breeding to excess? These questions are increasingly poking into public debate, and from odd directions. Phillip Mountbatten – husband of the British monarch Elizabeth Windsor – said in a documentary screened this week: "The food prices are going up, and everyone thinks it's to do with not enough food, but it's really [that there are] too many people. It's a little embarrassing for everybody, nobody knows how to handle it." He is not alone. A strange range of people have voiced the same sentiments over the past few months, from the Dalai Lama to Hu Jintao, from Conservative mayor Boris Johnson to Democratic Governor Bill Richardson.


They start by listing the sums, which are indeed startling. Every year, world population grows by 75 million people – equivalent to another Britain and Ireland whooshing fully-populated from the oceans. At the turn of the 18th century, there were 600 million people on earth. At the turn of this century, there were 6.6 billion. By the time I am in my sixties, there will be more than nine billion – at which point there will be more people alive simultaneously than in the first 17 centuries after Christ combined.

The overpopulation lobby say this will inevitably leave more and more people chasing after a diminishing amount of resources on an ecologically-ravaged planet. At their most pessimistic, they say human beings will, in the long sweep of planetary history, look like a big-brained version of a locust cloud. They eat everything in sight and multiply fifty-fold – until they have consumed everything, when they turn in desperation on each other, munch off their siblings' heads, and then fall out of the sky dead.

They say with a frown that this global swarming is driving global warming. How can you be prepared to cut back on your car emissions and your plane emissions but not on your baby emissions? Can you really celebrate the pitter-patter of tiny carbon-footprints?