Talking about population gets you into trouble. Mention it and you're 'anti-human', an 'extreme Green', 'racist', 'anti-immigrant', or dictating to developing countries how they should behave. You're told the real issue isn't over-population, but lack of equity in distribution of resources.
It's hard not to sound misanthropic when discussing population. Conservatives accuse you of favouring abortion, contraception, fertility control and sterilisation in developing countries, and progressives say you're a cultural imperialist diverting attention from social justice.
Discussion of population lost respectability in the mid-1980s following the sterilisation policies of Congress Party governments in India and the one child policy in China. In contrast Thailand, Indonesia and Bangladesh have run successful population programs without draconian measures.
There are also powerful vested interests maintaining high rates of immigration in Western countries which have reached zero population growth. Business wants to maintain consumers for goods and services, regardless of the pressure this puts on local environments. In market-oriented thinking new immigrants add to the pool of consumers rather than impacting a fragile environment.
The result: politicians avoid population issues like the plague (except when, like Kevin Rudd and Finance Minister Lindsay Tanner, they're beating the drum for an even 'bigger Australia').
The consequence is our country has a higher per capita growth rate from immigration (2.1 per cent for the year ending June 2009) than Indonesia. This will have a very large impact on Australia's attempt to cut greenhouse gas emissions because so many of these people are coming from countries with a lower standard of living and a much lower contribution to global warming.
These kinds of disconnects in policy formulation occur because immigration and population have become taboo topics among bureaucrats and politicians who fail to see, or are unwilling to tackle, the mutual contradictions involved. Global warming is lost between the discontinuities.
The great religious traditions have only the most rudimentary views on the morality of population limitation. Because the religious traditions have been largely absent from this debate, it has been mainly carried on in secular and economic terms by biologists, demographers and economists.
The reason why religious people have avoided this issue is simple: it is a theological and moral minefield. Embedded in it are a whole range of acute ethical issues and challenges to ingrained attitudes.
A basic moral conundrum concerns the ethical issues involved in inter-generational rights: if we consume so many resources now that the quality of life of future generations is compromised, are we acting in a morally responsible way? I think we do have serious and binding moral obligations to those who come after us. They have as much right to a quality of life as us.
Then there's the moral issue of the imbalance between the living standards of developed regions such as North America, Western Europe and Australia and the 20 per cent of people who are starving or under-nourished.
Does this imbalance create an ethical demand that developed countries lower their standard of living and dispose of food surpluses to needy countries at concessionary prices? Is there a basic moral right, overriding the powers of nation states, to allow migration from countries of over-population and chronic shortage to those with apparent space and surplus food?
And what about the right to reproduce: what limits can the community place on the rights of individuals to decide their fertility and family size? Women play a key role in this. We already know that women will use the educational opportunities they receive to improve standards of living for their families; then, with a consequent reduction in child mortality, they are more willing to limit conception.
Whenever women are liberated with guaranteed rights and equality, the birthrate has been reduced. They also need employment and interests beyond the home.
There have been real successes in improving the lot of women. Between the late 1960s and 2000 the total birthrate of developing countries has been reduced from six to three births per woman. While Catholicism is widely criticised for its opposition to contraception and abortion, the contribution of religious orders and Catholic care agencies to education and higher standards of literacy, health care, development aid and the breaking down of social and class barriers have been important contributions to changing the role of women.
While Catholicism and Islam are often blamed for imposing oppressive conditions on women, the actual oppression that they experience is the result of tribal and patriarchical cultural attitudes. Sure, religion is used as a major component in the enforcement of the social mores of male control, lack of female education, and high fertility. Clearly they reinforce each other but it is unfair to blame religion for the whole problem.
So a basic element in a morality of population is education and liberation of women, giving them control of their fertility. Religious people must be proactive in emphasising women's rights as a moral issue, and prepared to confront unequivocally the abuse of women. And we must recover a proper biological perspective: we aren't the sole reason for the earth's existence, just part of it, perhaps even a minor part. We need to recover humility.
Author and historian Paul Collins is a former specialist editor- religion for the ABC.