As Pope Francis addresses a joint meeting of Congress today (Sept. 24), scientists are praising his encyclical on climate change — with a few caveats about population control.
A series of editorials published today in the journal Nature Climate Change applaud the pope's in-depth missive for his calls for collective action on warming temperatures, which are driven by fossil-fuel combustion. The encyclical was a "decisive democratic act," wrote Anabela Carvalho, a communication sciences professor at the University of Minho in Portugal. It was "passionate and compelling," added Stanford University ecologist Paul Ehrlich and University of California, Berkeley environmental scientist John Harte in their co-authored editorial.
But the researchers warned that change would be difficult in the face of an entrenched status quo. And it might not be possible, some said, to save the world without contraception, which the Catholic Church opposes. [Catholics in America: Views on Contraception & Other Social Issues (Infographic)]
"Pope Francis needs to heed his own comments on the church's 'obsession' with contraception and abortion, and assume a leadership position in support of women’s rights and family planning," Ehrlich and Harte wrote.
The population question
Contraception is linked to climate change, because peoplethrough their activities and patterns of consumption, produce greenhouse gases. A 2009 cost-benefit analysis funded by the U.K. charity Optimum Population Trust makes this connection clear. That research estimated the cost of providing contraception to women who want to use birth control but don't have the opportunity. Meeting this need between 2010 and 2050 would decrease projected carbon dioxide emissions by 34 gigatonnes (34 billion tonnes), the study found. This translated to a cost of $6.46 per tonne of emissions reduction. For comparison, the use of low-carbon technologies such as wind power and carbon capture for coal plants would cost $32 per tonne, according to the same study. [What 11 Billion People Mean for Climate Change]
Pope Francis, a chemist by training, drew heavily from the realm of science in his encyclical, which is a letter to the bishops of the church. He condemned the doubting of climate change, cited concerns about diminishing biodiversity and even called for more green space in cities, which has been shown to boost health and happiness.
The pope also signaled, however, that he would not be reversing Catholic teachings on contraception, arguing against population control as a major solution for climate and environmental woes.
"Instead of resolving the problems of the poor and thinking of how the world can be different, some can only propose a reduction in the birth rate," Francis wrote. "At times, developing countries face forms of international pressure which make economic assistance contingent on certain policies of 'reproductive health.'"
Quoting Pope John Paul II, Francis went on to say that demographic growth is compatible with development, calling for an equitable distribution of resources rather than a focus on birth rates. [11 Billion People: 7 Ways Population Impacts the Planet]
Here, the pope and many scientists part ways. Ehrlich, in particular, has been warning of the dangers of overpopulation since his 1968 book "The Population Bomb." Though dire effects like global famine have not come to pass thanks to advances in agriculture, the growing population has produced problems, Harte told Live Science.
"The world hasn't collapsed, but we have on the order of a billion people who are underfed and undernourished in the world, and that's a serious problem," he said.
The United Nations projected in 2013 that the world population will reach 9.6 billion by 2015. While fertility rates have fallen in most developed countries, fertility has remained higher than previously estimated in sub-Saharan Africa.
A place for family planning
The pope said that if developed countries consume less, and resources are shared more, population growth can continue. However, most environmental scientists or development experts don't agree with this view. The United Nations puts family planning front and center in its quest for sustainable development.
"Policies to increase the availability of safe and effective contraceptives and accessibility to family planning programs and reproductive health care have been instrumental in facilitating reductions in fertility," according to the agency's 2014 World Population Report. A 2005 report by the World Health Organization (WHO) found that contraceptive use went up from about 10 percent of women in the early 1960s to nearly 60 percent by 2000. In the same time period, the fertility rate dropped from 4.97 children per women to 2.69 children per women.
In 2014, the U.N. reported, 60 percent or more of married or coupled women used contraceptives across the globe, with the exception of fast-growing Africa.
There, contraceptive usage by coupled women hovers just over 30 percent. The continent also has a high level of "unmet need," defined as the gap between those who use contraception and those who say they want to, but don't. In Africa, the percentage of women reporting unmet need for contraceptives clusters around 30 percent or more. In Europe and North American countries, by comparison, it's more like 10 percent.
Other population influencers
Although contraception plays a large role in birth rates, birth control availability isn't the only factor that determines family size. Culture, religion and the economy all play roles in whether people use birth control, even if it's available.
Researchers found that in Bangladesh, for example, economic factors, particularly education of women and a shift to urban dwelling, were the strongest drivers of family size changes. Health care access and infant mortality rates had effects, but they were smaller, the researchers reported in their 2013 study. Culture played a small role and influenced contraception access, the study found. The take-home message, the researchers told Live Science at the time, was that educating women is the best way to decrease population growth.
Some experts have argued that, in the grand scheme of things, the overconsumption of developed nations matters more than the population growth in poor countries. Most of the fastest-growing nations have low per capita greenhouse gas emissions, David Satterthwaite, who researches climate change adaptation at the International Institute for Environment and Development in the United Kingdom, told Live Science in 2011. In that sense, Pope Francis' call for more equitable distribution of resources makes sense: If developed countries cut back on emissions enough, they could make up for the lower-emitting but fast-growing underdeveloped nations.
But sub-Saharan Africa wants — and deserves — to develop, too, Harte said. How the continent ends up affecting climate change depends on whether those nations choose sustainable, green energy or "make the same mistakes we did in rich countries and burn coal and oil," he said.
Sustainable and equitable development is less likely to occur against a backdrop of population growth, Harte said.
"All of the evidence at hand is that in parts of the world that are growing the most rapidly … the plight of the people is worse, and the amount of time and energy they have to deal with issues like more fair and just government is reduced," he said.
Thus, Harte said, it's unrealistic to call for fair distribution without also working to slow population growth.
"We feel very positive about what the pope has done, but we could have given it three cheers instead of two if he had only dealt with women's rights and population," he said. "We understand that this goes against a lot of church dogma, yet I think it's incumbent on us to call the church to task for not revising and updating its ideas about what constitutes personal freedom for women and families."
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