As Pope Francis was returning to Rome from the Philippines last month, he told journalists about a woman who had had seven children by caesarean section and was now pregnant again. This was, he said, "tempting God". He asked her if she wanted to leave seven orphans. Catholics have approved ways of regulating births, he continued, and should practise "responsible parenthood" rather than breeding "like rabbits".
Francis' "rabbit" comment was widely covered in the media, but fewer reported that he had also said that no outside institution should impose its views about regulating family size on the developing world. "Every people", he insisted, should be able to maintain its identity without being "ideologically colonised".
The irony of this remark is that in the Philippines, a country of more than 100 million people, of whom four out of five are Roman Catholic, it is precisely the Church that has been the ideological coloniser. It is the Church, after all, that has vigorously sought to impose its opposition to contraception on the population, opposing even the provision of contraceptives by the government to the rural poor.
Meanwhile, surveys have repeatedly shown that most Filipinos favour making contraceptives available, which is not surprising, given that the Church-approved birth-control methods mentioned by Francis are demonstrably less reliable than modern alternatives. It is hard to believe that if the Philippines had been colonised by, say, Protestant Britain rather than Catholic Spain, the use of contraception would be an issue there today.
The larger issue that Francis raised, however, is whether it is legitimate for outside agencies to promote family planning in developing countries. There are several reasons why it is. First, leaving aside the "ideological" question of whether family planning is a right, there is overwhelming evidence to show that a lack of access to contraception is bad for women's health.
Frequent pregnancies, especially in countries without universal modern health care, are associated with high maternal mortality. Aid by outside agencies to help developing countries reduce premature deaths in women is surely not "ideological colonisation".
Second, when births are more widely spaced, children do better, both physically and in terms of educational attainment. We should all agree that it is desirable for aid organisations to promote the health and education of children in developing countries. The broader and more controversial reason for promoting family planning, however, is that making it available to all who want it is in the interest of the world's seven billion people and the generations that, barring disaster, should be able to inhabit the planet for untold millennia to come. And here, the relationship between climate change and birth control needs to be brought into focus.
The key facts about climate change are well-known: Our planet's atmosphere has already absorbed such a large quantity of human-produced greenhouse gases that global warming is under way, with more extreme heat waves, droughts, and floods than ever before. Arctic sea ice is melting, and rising sea levels are threatening to inundate low-lying densely populated coastal regions in several countries. If rainfall patterns change, hundreds of millions of people could become climate refugees.
Moreover, an overwhelming majority of scientists in the relevant fields believe that we are on track to exceed the level of global warming at which feedback mechanisms will kick in and climate change will become uncontrollable, with unpredictable and possibly catastrophic consequences.
It is often pointed out that it is the affluent countries that have caused the problem, owing to their higher greenhouse-gas emissions over the past two centuries. They continue to have the highest levels of per capita emissions, and they can reduce emissions with the least hardship. There is no doubt that, ethically, the world's developed countries should be taking the lead in reducing emissions.
What is not so often mentioned, however, is the extent to which continuing global population growth would undermine the impact of whatever emission reductions affluent countries can be persuaded to make.
Four factors influence the level of emissions: economic output per capita; the units of energy used to generate each unit of economic output; greenhouse gases emitted per unit of energy; and total population. A reduction in any three will be offset by an increase in the fourth.
In the "Summary for Policymakers" of its 2014 Fifth Assessment Report, the Intergovernmental Panel on Climate Change stated that, globally, economic and population growth continue to be "the most important drivers" of increases in CO2 emissions from fossil-fuel combustion.
According to the World Health Organisation, an estimated 222 million women in developing countries do not want to have children now, but lack the means to ensure that they do not conceive. Providing them with access to contraception would help them plan their lives as they wish, reduce demand for abortion, limit maternal deaths, give children a better start in life, and contribute to slowing population growth and greenhouse-gas emissions, thus benefiting us all.
Who could oppose such an obvious win-win proposition? The only naysayers, we may suspect, are those in the grip of a religious ideology that they seek to impose on others, no matter what the consequences for women, children, and the rest of the world, now and for centuries to come. ©2015 Project Syndicate
Peter Singer is Professor of Bio-ethics at Princeton University and Laureate Professor at the University of Melbourne. His books include 'Practical Ethics', 'Rethinking Life and Death', and 'The Life You Can Save'.