As a result, state and local planning schemes for housing, water supply, electricity, health care, education and transport are becoming redundant almost before the ink is dry on them. Victoria's latest State of the Environment report concludes that development on Melbourne's urban fringes is driving the loss of natural habitat and biodiversity, degrading waterways, taking up good agricultural land and creating a host of other pressures.

In this context, the release of the book Overloading Australia by Mark O'Connor and Bill Lines has sparked another round of debate about Australia's population. Some commentators have been quick to detect a murky agenda of xenophobia hovering behind a green cloak in the population debate. They are right to be suspicious. Population control movements have been associated in the past with anti-migrant agendas and coercive birth control policies in developed and developing countries. In light of this dark history, it is critical for those who advocate population stabilisation to reject any such association unequivocally.

And yet it is possible to argue for a sustainable population policy that includes some limits on migration without being anti-migrant. When I was in law school in the US, I spent many late hours volunteering at a legal clinic that represented refugees making application for asylum. I feel deeply that one of the true measures of a society's ethics is how it treats refugees and others on the wrong end of the modern global economy.

Many people may not realise that in recent years more than half of Australia's permanent migrants have been through the skilled migration stream, compared with only 7 per cent of the total being humanitarian migrants and 25 per cent family migrants. So having a sound population policy that brings migration back down to reasonable levels does not mean shutting the door on refugees. In fact, Australia could even increase its refugee intake, while still tracking for stabilisation of the overall population by about 2050, if we reduce skilled migration substantially.

Since most of the recent increase in migration is attributable to perceived economic requirements, not humanitarian or family obligations, perhaps we should scrutinise more closely the claims by industry that they are needed to meet ''skills shortages''. One wonders whether such claims are really just code for ''lower wages''. The truth is, the rapid increase in skilled migration is being used as a crutch for the economy, a way of providing a short-term boost to things like housing construction and retail demand but without any serious reckoning of the long-term consequences. Relying on migration to prop up sectors of the economy also diverts us from the task of devising more sustainable solutions.

In trying to ease the pressure overpopulation and excessive consumption are having on our planet and its ecological systems, we must debate immigration and demographic patterns while keeping Australian values of justice, equity and fairness front and centre.

Those who are sceptical of calls for a sustainable population policy are also fond of pointing out that our modern, high-consumption lifestyle is the most pressing cause of our environmental problems. They are correct that we must tackle our high pollution and consumption levels and shift to a more sustainable lifestyle. According to the World Resources Institute, Australia's greenhouse pollution level of 26tonnes of CO2-e per person per year is double Germany's, six times China's and 11 times Indonesia's.

But, while a lower-impact way of life must be a top priority, we must also understand that a rapidly growing population will make that transition much more difficult. For instance, in 2002, a CSIRO report analysing the possible consequences of different population levels for Australia found a 28 per cent increase in the nation's population by 2050 would lead to 20 per cent more energy use and greenhouse pollution, 25 per cent more urban water use and higher food import requirements (especially for fish and vegetables), among many other impacts. The sobering reality is that the growth of a consumption-intensive population in Australia is seriously damaging our environment. Despite these pressures, Australian governments have continued to pursue high-population-growth strategies or have had no coherent demographic policy at all. The baby bonus (or the new plasma screen bonus, as they call it at one major retailer) is an example of such a misguided policy.

Australia now needs to shift its focus to policies that seek to match human populations and consumption levels within nature's carrying capacity, while transforming our economic and social systems to function within the limits of ecological systems.

We should also support programs in high-fertility countries that improve education and maternal and child health care as well as provide sustainable economic opportunities. The good news is, these programs are the most effective means of reducing fertility and promoting sustainable development. We can achieve a sustainable population while discharging our ethical obligations to accept refugees and play a positive role internationally. It is not only achievable: our future may depend on it.

Charles Berger is director of strategic ideas at the Australian Conservation Foundation.