Living sustainably, whilst a noble goal won't float with us Westerners who love our energy intensive lifestyle such as international air travel for holidays and academic conferences.

Living sustainably is tough. I lived sustainably when growing up on a farm in the Wimmera. I started work at 4 years old getting the wood and progressed from there. Milking cows, cutting and stacking hay, cutting and splitting wood, dragging feed around the farm on a tractor, turning the milk separator to get cream, then watching Mum take hours to make a pound of butter, killing sheep and burying their guts in the back paddock. Then I turned 10 and the real work began. Wimmera farm boys knew that when the school bus slammed shut behind them, their second shift began.

Living sustainably and wanting to fly breaks Dean's Law which states: "The more efficient a device is made, the more devices will be made and used resulting in a greater use of the resources to make and use the device than if it had remained inefficient in the first place."

Example: In 1960 the Boeing 707 introduced modern jet travel. The 707 used about 3 times the fuel to fly a passenger across the Atlantic than a modern, fuel efficient Boeing. That's good except for one small detail. The amount of jet fuel used in 2010 is approximately 100 times the amount used in 1960. (The law applies to virtually every product; plastic, car components, electricity etc)

Living sustainably will only happen when the second Dean's Second Law applies: "We will go sustainable when we have sucked every last hydro carbon out of old mother earth and not before".

I trust the above helps.

Thank you

Gerard Dean
Glen Iris

Thanks Graeme for a fairly balanced view of the issue. The graph Alex Cannara refers to suffers from necessary compression of the x-axis (timescale) given the period it covers. Your 123, 32, 15, and 13 years for the second to fifth billionth persons does provide a better sense of scale than the launch pad to which Alex refers - not criticising Alex or the Science Mag, just pointing out that graphs and scale sometimes need unpacking.

"Fertility decline, especially in Africa, hasn’t proceeded as rapidly as was anticipated." besides being a clarion call to address poverty, aid from all sources must be decoupled from conditions imposing restrictions on birth control: the USA and the Vatican being the major offenders in this respect. With endemic warfare and implacable itinerant male employment, women being able to control their own fertility is a necessary adjunct to poverty alleviation in order to achieve lasting gains in welfare.

The greatest danger and the most tempting is that the problem is so overwhelming that the developed world throws up its hands and decides does not do enough to answer the challenge.

I noted that the Prime Minister several weeks back offered that we would/could/should be the food bowl for the world. Yes, that is noble thinking and a fine goal to work towards, if that was how our food producers also saw it. However, to do this, doesn’t it mean that the volume in food production requires that we should be able to be entirely self-sufficient and feed ourselves from the continent, which as a country we don’t do any longer?

Once upon a time, grapes and cherries, used to be grown in abundance here. Along with pineapples, which in a good year would be dumped off at the end of piers in Queensland, because the bumper crop meant this fruit would be selling at prices unprofitable to farmers to transport it to markets in the south.

The grapes and cherries came to mind because at the market last week cherries was selling for $12 a kilo and they came from the United States while seedless grapes of the Thompson variety also imported from the US was selling around $5 a kilo.

However, the irony is that the US imports grapes from Chile most of the year and cherries when you can get them for three weeks of the year in the American summer (around July 4) comes from southern Chile. So we import grapes, which we grow in abundance most of the year along with cherries, albeit seasonal, for much longer than the US while the US would rather sell their produce to us rather than sell it at lower prices in their own markets.

So given that the population will grow to 10 billion as Professor Hugo suggests between 2050 and 2100, food distribution is in for some serious reorganization. A serious reorganization, if we ever hope to tackle the problem and provide food to all, when in fact even though up to 825 million people don’t get enough of the cereal grain crops grown today, which would adequately feed them.

But it seems to me, that if a serious reorganization of food distribution was to occur, it may also need a redistribution of priorities by food producers of crops grown in order to satisfy the need and provide food security for all.

Also, does it also mean that instead of things like grapes and cherries, we devote food production to necessary foods such as grains and rice? Also, does it mean less focus on meat and meat products, which is very intensive agriculture?

I don’t see this as being easy to argue beyond governmental aspirations. Would food producers be willing to reconsider growing the current crops for population growth and forego the inherent profits, which come with it and convert to the production of necessary crops to feed and nourish all?

It probably depends on farming no longer being a family occupation, but given over to agribusiness and farming corporations, which use the farming shortcuts such as genetically modified grains and seeds and the use of pesticides to guarantee, successful crops annually.

I don’t see realignments in food production and food distribution happening easily and certainly not without a wider public and popular debate. But the time is now to begin considering what a new regimen looks like in food production, as sudden change could mean resistance and opposition from growers.

Coming from a generation of graziers, change is not usually welcomed, even if is for necessity.

There's much to like in this brief analysis of the world's population situation. Yet I had two caveats.

1. The conclusion that stabilising world population "can be best achieved by improving the lives of people in low-income countries" which persuading those in richer countries to consume more sustainably combines a number of good aims, and ends the piece on a suitable feel-good tone. But is it actually true? Depends a bit on what is meant. I wouldn't want to wait until the rich reduced their consumption before seeking to reduce populatin growth in poorer countries -- whose people of course don't aim to remain poor. Still, what about those rich countries with third-world rates of population growth -- notably Australia, Canada and the USA. Why is the growth of their supe-consuming populations not mentioned as a problem?

And not all demographers agree that making the people in poor countries affluent (assuming "we" could) is the prime or easiest way to reduce their family size. (Remember that photo of the huge and very affluent Saudi family with a dozen children, and including a 15 year-old Osama bin Laden.) See also the discussion of Virginia Abernethy's views in my and William Lines's Overloading Australia. p. 69, 201.

2. I am a little wary of "aging scare" statistics like "in 2070 ... there will be only three working age people to every 2 people aged 65+." The issue is rather, what is the proportion of working age people to those EITHER too young or too old to work. In general those scenarios that assume very low birth rates and a lot of older people also produce fewer young people -- and young people (children) not only can't work (unlike many people over 65, e.g. myself) but need constant attention that pulls adults out of the workforce. Is there equal concern about countries like Nigeria today where there are very few people to old to work, but vast numbers too young?