It's time to cut our fertility rate

Indeed they won't, and so I fear for my grandchildren. A world built on the ready availability of cheap energy is going to have to either change fast, or fail. When oil, which supplies 95 per cent of our transport fuel, enters its inevitable decline, the economy may well collapse. We might avert it by a rapid move to renewable energy and the electrification of transport, but I doubt that politicians will have the political will to provide the money for this to happen. What is needed, for instance, to get zero emissions by 2020 by investing in wind farms and solar thermal energy, is the equivalent of the funds devoted to the National Broadband Network, but those same funds every year for ten years!

Paul Gilding was right to name his latest book "The Great Disruption". It's almost inevitable that as energy supplies decline and we are hit increasingly with the effects of climate change, that there will be a great disruption to our economy and society.

So what's this got to do with my granddaughter having a sister as life companion? A lot. We are entering a period of contraction, and that is going to have to apply to family size as well. The combined effects of climate change and declining oil supplies mean we will not be able to support the same numbers of human beings on this planet that we have now. It means we have to enter a period of population decline (sorry demographers) until we reach a population that is truly within the carrying capacity of the planet.

In the US, Dr Jack Alpert (www.skil.org) believes we may only be able to support a population of 32 million (not billion, 32 million!) at an average standard of living of an American today. I personally have more faith in renewables to take us into a new future, but I suspect that we have to seriously look at what he is advocating. And that means fairly rapid population decline. While I think a one-child policy is too radical, I believe that a fertility rate of 1.5 is not unreasonable, that is, half of couples having two children and the other half only having one. Or maybe we can have more than half having two children as long as a significant proportion of the population chooses not to have children at all. My daughter is a school teacher and loves children but doesn't feel the need to have her own. "Mum", she says, "…at 3pm I don't want to know about having my own children," she says. Fair enough.

This is not an anti-child tirade. I love children more than most. I get excited when friends have their first or second child. But the days of the third child are well and truly over. I once said those who have a third child are environmental vandals. It still holds true. The only options in these days of coming difficulties are zero, one or two children. If you can't bear it, adopt a child who really does need love and a home.