Earlier this month, Pope Francis made news when he said that not only was climate change real, but it was mostly man-made. Then, last week, he said that couples do not need to breed like rabbits but rather should plan their families responsibly albeit without the use of modern contraception.

Though the pope did not directly link the two issues, climate scientists and population experts sat up and took notice. That's because for years, they have quietly discussed the links between population growth and global warming, all too aware of the sensitive nature of the topic. Few of them can forget the backlash after then-Secretary of State Hillary Rodham Clinton said in 2009 that it was strange to talk about climate change without mentioning population and family planning. Critics immediately suggested that she was calling for eugenics, thus shutting down the conversation and pushing the issue back into the shadows. The pope's support of smaller families might help that discussion come back into the light, where it belongs.

Sensitive subject or not, the reality is that unsustainable human population growth is a potential disaster for efforts to cut greenhouse gas emissions. These days, the biggest population growth is occurring in developing nations, which is why any discussion must be sensitive to the perception that well-off, industrialized nations the biggest climate polluters, often with majority-white populations might be telling impoverished people of color to reduce their numbers. In fact, person for person, reducing birth rates in industrialized nations has a bigger impact on greenhouse gas emissions because affluent people use more of the Earth's resources and depend more heavily on fossil fuels.

In other words, population is not just a Third World issue. More than a third of the births in the United States are the result of unintended pregnancies, and this month the United Nations raised its prediction of population growth by the year 2050 because of unforeseen, rising birth rates in industrialized nations. So even though the highest rates of population growth are in the poorest and least educated countries Africa's population is expected to triple by the end of the century any attempt to address the issue will have to target the industrialized world as well.

By 2050, world population is expected to increase from its current level of about 7 billion to somewhere between 8 and 11 billion. According to a 2010 analysis published in the Proceedings of the National Academy of Sciences, keeping that growth to the lower number instead of even the mid-range 9.6 billion could play a significant role in keeping emissions low enough to avoid dangerous levels of climate change by 2050. A more recent report, though, casts doubt on whether it would be possible to bring about dramatic enough changes in population quickly enough to hold the total to 8 billion.

Another 2010 report, by the nonprofit Center for Global Development in Washington, D.C, predicted that fast-growing developing countries will become the dominant emitters of greenhouse gases within a generation. That's partly because of their rising populations but also because of their poverty; they are less able to afford solar energy projects or other investments in non-fossil energy.

The report also notes that these countries and their people are far more vulnerable to the effects of climate change. A disproportionate number of impoverished countries are in low-lying areas where rising sea levels are expected to cause disastrous flooding. Agricultural productivity is expected to fall 40% in India and sub-Saharan Africa by the second half of this century.

The population issue is just beginning to get some of the public attention it deserves. The most recent report by the Intergovernmental Panel on Climate Change, the United Nations' board of climate experts, included concerns about population size, saying, Globally, economic and population growth continued to be the most important drivers of increases in CO2 emissions from fossil fuels. For the first time in its five years of producing such reports, the panel acknowledged that family-planning programs could make a real difference, both in slowing the rate of warming and in helping vulnerable nations adapt to its effects.

And progress can be made without draconian or involuntary measures. According to Karen Hardee, director of the Evidence Project for the nonprofit Population Council, developing nations are already beginning to recognize the usefulness of family planning in preventing hunger and crowding and in combating climate change. She cites Rwanda, Ethiopia and Malawi as countries that are taking the first steps on their own.

But they and other nations need assistance on two fronts: education for girls and access to free or affordable family-planning services. The benefit of even minimal education is startling: Women in developing countries who have had a year or more of schooling give birth to an average of three children; with no schooling, the number is 4.5. Add more years of schooling and the number of births drops further. Women who have attended school also give birth later in life to healthier children.

Link:

Why we need to address population growth's effects on global warming