Session 6: Questions/discussion

Alex Wells: We can point to plenty of examples in both the ancient and the modern world where we have established a clear causal link between population growth and negative impacts on the key social-environmental indicators. Are there any examples you have come across, either nationally or internationally, where there is a clear causal link between population growth and improved social-environmental indicators?

Tony McMichael: A challenging question. One example that is explored in the literature a little – and I am afraid I can't speak about it in great detail – comes from Kenya, where I think it is the Muchakos area. The experience over a number of decades has been that indeed with some improvements in environmental management there has been quite an increase in the local population, in ways that have apparently been consistent with maintaining, perhaps even improving, environmental conditions and maintaining social harmony. So the sort of scenario that you describe is attainable. But I am afraid I can't generalise beyond that.

Tony Capon: I think you have highlighted very clearly, Tony, the limitations of the current practice within epidemiology to grapple with these issues. But I wonder if you would comment on how you might go about transforming the profession to ensure that in 20 years' time it looks quite different from what it does now.

Tony McMichael: Well, that would be a radical thing to do, to transform it in a way that makes it quite different. I think what we have got to do is to extend the boundaries. I feel quite strongly that those of us that are working in the health sciences need to understand that there is an underlying and fundamentally important ecological dimension to human biology and health – that this is something that operates not just at an individual level, which is where many of my colleagues are most comfortable working because you can make higher-quality measures and get more quantifiable relationships, but we need to be prepared to work within more complex research contexts, exploring perhaps within more of a systems context the ways in which these larger-scale environmental and social processes impinge on patterns of health and disease.

That is rather unsettling for a lot of us that have been trained as quantitative, empirical scientists, because it involves much more complexity, much more uncertainty. And, necessarily, it involves looking to the future and saying, 'What are the likely consequences of some of these changed processes that we now see arising?' So it is really a matter, I think, of having epidemiologists and other population health researchers understand that we now have on the research agenda a range of serious questions that society is posing to us about what are the likely consequences for human health of a change in the world's climatic and associated environmental conditions.

I think many of us have blind spots about this. We find it hard to see that it is an important and urgent part of the emerging agenda. In fact, I was having a discussion with a quite senior member of the government a few weeks ago, and we were talking about the potential health impact of global climate change. It was interesting that he was very ready to concede that things that act directly, like heatwaves killing people, or even the southward spread of mosquitoes in Australia as the climate changes, were recognisable impacts on health. But when we began to talk about the ways in which, perhaps, an El Niño-driven intensification of droughts in Australia would affect rural economies and rural morale, and how that might be reflected in things like suicide rates or mental health problems, he found that rather difficult to see as a health consequence of climate change. He said, 'That's really an economic impact, isn't it?' and I was saying, 'Well, we have got to think in these longer causal chains. We've got to understand that these are shifts in the conditions of living that flow through and have consequences for health.'

And I think you would appreciate that modelling those sorts of things is not the sort of thing that, for the moment, population health researchers are very good at. We have got to embrace that sort of question in that sort of analytic approach.

Barney Foran: Tony, from an epidemiologist's point of view, or a long-ranger like yourself, are the ageing crisis in Australia and the intergenerational report a beat-up, or are they as profoundly bleak as our Treasurer would sometimes have us believe? I guess I am trying to get your feelings for whether we are going to be older but weller, as opposed to older but crooker. What is your feeling on the intensity of the ageing crisis?

Tony McMichael: Well, this is taking me outside my area of expertise. Certainly it has been true that in the last couple of decades quite a bit of work that has been done – and I think demographers present would be aware of some of this – has indicated that even though physical life expectancy has been continuing to drift up in most countries of the world, of course including the richer developed countries, the expectancy of healthy life has not been increasing. So the number of years being lived with disability or chronic disease has been tending to increase in recent times. Indeed, in one or two countries there has actually been a fall in healthy life expectancy while there has been an increase in physical life expectancy.

This is a reflection of, on the one hand, I suppose, the capacity of the health care system to avert death by things like coronary bypass surgery, treatment of cancer and so on, while on the other hand we have been living, and I think continue to live, in societies where many of the things that we do increase the risks of chronic disease processes in later adulthood. And of course the one that is being talked about increasingly now is the extraordinary rise in the prevalence of overweight and particularly obesity, which we can foresee will produce a sort of tidal wave of type 2 diabetes and associated diseases over the next several decades.

We need to recognise that we are going to have to think – again in these ecological terms – about adjusting our ways of living, such that we don't get fat. If you read the editorial in this morning's Australian you get the sort of depressing commentary that occurs all the time, saying, 'Look, solving obesity is easy. We just need to have the government give individuals correct information about how much they should eat and how much exercise they should do.' We know that's wrong. We know the problem is that we have systematically changed the way we live over the last few decades, so that there is a systemic energy imbalance in modern society and we get fat. And that's to do with things like urban planning and transport systems and so on, it's not to do with what individuals do or don't know. We're not getting sillier; we're getting smarter but we're also getting fatter. So it is to do with environmental and ecological circumstance.

So again I would like to have the debate focus on those sorts of things so that we can understand how societies can actually avert the onset of those sorts of later-life disease processes, so that, as we get older, we won't in future get sicker.

John Beaton: This is not a question but a statement. I was astonished to hear moments ago, in response to a question, if I understood it correctly, about whether there is evidence for populations who have grown and whose lives have improved – was that the question? – a deafening silence.

This did astonish me, because this is the history of the human population since the end of the Pleistocene and increasingly so from the middle of the Holocene to the present. The quality of life that we all now enjoy, although we measure it in ways that sometimes shame us – the wealth et cetera – is something that we have in every country embraced. I know of not a single example of a population who has moved from a foraging or hunting and gathering environment into a horticultural, sedentary environment and has then gone back to foraging and hunting and gathering unless they have been absolutely forced to. Similarly, I do not see people looking to move from a high-tech age, an industrial civilisation, to an agrarian one without being indeed forced to.

The question is not whether we are, in fact, increasing in quality of life with population density and numbers, because I think all the evidence says that we are. The question is: how do we try to understand a point at which we can find stasis, at which we can find an equilibration between resources and environment?

Again I want to point to the absolute need for all the other disciplines to reach out and grab an economist by the hand – I am not an economist, by the way, but I highly recommend we do that – particularly when I reflect back on ecology and what we have learned about foraging and the way that humans extract their livelihoods from the environment. Let me put it this way. The anthropologists who work in this field now have derived their models, or reinvented them, let me say, from the population ecologists and population biologists of the '60s, '70s and '80s, and they got their models and their ideas – I will argue this with anybody who cares to argue it – from the economists. It was all about what you can catch, how much energy you need to expend to catch something which is in fact your sustenance, what the costs were, et cetera.

So the issue is that bridging the disciplines in this debate means that we have to understand the fundamental economics of getting a living. And the only question is: at what level are we going to be satisfied?