It's time to cut our fertility rate

I tucked my two grand-daughters into their respective beds, read them each a story and turned out the light. An hour later when I went to check, the two year old had crept into bed with her four-year-old sister and both were contentedly asleep. How lucky, I thought, to have the life-long companionship of a sister.

That response, of course, may have just been my cultural conditioning. Only children were the objects of pity within my extended family when I was growing up. It was assumed that no-one could possibly want to have only one child – there had to be a physiological reason for not having more.

It was not until I became a mother myself that I met a couple who were very assertive about only having one child. They were both healthy and could have had more but chose not to. Indeed, they were angry with those who put pressure on them to have more than one. Part of it was economic – by only having one it meant the wife could stay home in their smallish house and not go out to work. But it was also psychological – they felt they had fulfilled all their parental urges by having just one.

In the end, it was decision I made myself. After reading Paul Ehrlich's Population Bomb in 1970, I resolved to only have one biological child. My maternal urges were unsatisfied, however, with just one. Only after adopting three children and long-term fostering another did I decide that my maternal urgings were at last satisfied.

Some years ago now, the then Federal Treasurer Peter Costello called for couples to have a third child (for the country) and the Howard Government introduced the baby bonus. Whether it was causation or correlation, Australia's fertility rate went from 1.73 (children per woman) in 2001 to almost 2.0 in 2008 before dropping back to 1.89 in 2010.

Demographers like fertility to be as close to replacement (2.1) as possible so that age cohorts remain more or less equal until those in their seventies and eighties start dying off. It is certainly easier to plan if you know how many schools for children and nursing homes for the elderly are needed. What demographers thought about Costello's call for fertility to be pushed towards 3 rather than mere replacement was anyone's guess, though no doubt they were happy to see it lifted from 1.7 and closer to replacement.

Demographers are the good guys, at least relative to economists. Traditional economists like Costello want more population growth to 'grow the economy', irrespective of whether or not that translates into increased GDP per capita, and irrespective of whether or not GDP is a true measure of human well-being. Demographers, on the other hand, want stable numbers.

Economists may well have been the good guys when human numbers on Planet Earth were small and growth in numbers allowed societies to reach critical mass for proper functioning of towns and cities. But that is no longer the case. We just passed the seven billionth person milestone and look set to reach eight billion by 2025. Of the seven billion, about one billion are chronically hungry. We passed the bio-carrying capacity of the planet back in 1979 and are exceeding it by one per cent a year such that we now need 1.4 planets to maintain current average standards of living, never mind lifting two billion people out of poverty.

Add to this the twin converging catastrophes of climate change and declining oil supplies, assuming we have passed the peak of conventional oil. (Currently, our conventional oil supplies are being augmented by oil from non-conventional sources such as deepwater, Arctic and tar sands, but these will only ever supply perhaps 5 million barrels of oil a day – a fraction of the 87 mbd currently used). Crunch-time will probably hit around 2015 when Saudi oil starts its inevitable decline. And with the decline of oil will come the ability of the world to feed itself and to maintain its current population, for agriculture as we know it in industrialised countries is heavily dependent on oil.

As for climate change, the good news coming out of the UNFCCC talks in Durban was that they have agreed to a legally binding treaty before 2015. The bad news is it will not be enforced before 2020. Meanwhile the International Energy Agency has warned we already have the power stations and factories in place such that, by 2017, anything more will push us into more than two degrees ('safe') of warming. On current trends, we're headed for four degrees warming.

Not sure what four degrees of warming means? According to Mark Lynas, author of 'Six Degrees', it will mean the disintegration of the West Antarctic ice-shelf and sea-level rises of a metre every 20 years. That's not just goodbye to Tuvalu and Kiribati, it is good-bye to the major food-producing deltas and estuaries of the world such as the Mekong, the Red River and the Brahmaputra. Goodbye to much of Bangladesh with its current population of 142.3 million and still growing by 2 per cent a year (doubling time 35 years).

In my Christmas letter this year to numerous friends and relatives, I ended with the warning: "I fear a deteriorating future with the two converging crises of climate change and peak oil looming large." A friend in London responded: "I expect the economic crisis will bourgeon before the other two become critical." It reminded me of the opening words of oil analyst Jeff Rubin at last year's annual conference of the Association for the Study of Peak Oil and Gas (ASPO) who drawled: "The next twenty years ain't goin' to be like the last twenty years."

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.