Slower population growth that leads to eight billion people in 2050 rather than to the currently projected 9.1 billion would save one billion to two billion tons of carbon annually by 2050, according to estimates by climate scientist Brian O’Neill of the National Center for Atmospheric Research and his colleagues. The subsequent savings in emissions would grow year by year ever afterward—while the billion-plus fewer people would need less land, forest products, water, fish and other foodstuffs.
Those improvements still would not be enough on their own to avert significant climate change. Other similar billion-ton savings in emissions (what Princeton University professors Stephen Pacala and Robert Socolow have dubbed “stabilization wedges”) are desperately needed and can come only from reduction in fossil-fuel consumption through energy efficiency, low-carbon technologies and changes in way of life. If two billion automobiles getting 30 miles per gallon traveled only 5,000 miles a year instead of 10,000, that change would save another billion tons of carbon emissions. So would replacing coal-fired power plants that produce 1.4 trillion watts of electricity with equivalent plants burning natural gas. But without a population that stops growing, comparable technology improvements or lifestyle downshifts will be needed indefinitely to keep greenhouse gas emissions sustainable.
The complications that population growth poses to every environmental problem are not to be dismissed. In fact, they are accepted and understood best by the governments of poorer countries, where the impacts of dense and rapidly growing populations are most obvious. During the past few years, most of the reports that developing countries have filed with the U.N. on how they plan to adapt to climate change mention population growth as a complicating factor.
Instruments of Policy
A commonsense strategy for dealing with rising environmental risk would be to probe every reasonable opportunity for shifting to sustainability as quickly, easily and inexpensively as possible. No single energy strategy—whether nuclear, efficiency, wind, solar or geothermal—shows much promise on its own for eliminating the release of carbon dioxide into the air. Obstacles such as high up-front costs hamper most of those energy strategies even as part of a collective fix for the climate problem. No single change in land use will turn soils and plants into net absorbers of heat-trapping gases. Without technological breakthroughs in energy or land use, only higher prices for fossil fuels show much potential for edging down per capita emissions—a “solution” that policy makers have yet to grapple with effectively.
Given the long-term contribution that a turnaround in population growth could make in easing our most recalcitrant challenges, why doesn’t the idea get more respect and attention? Politicians’ apathy toward long-term solutions is part of the answer. But the more obvious reason is the discomfort most of us feel in grappling with the topics of sex, contraception, abortion, immigration and family sizes that differ by ethnicity and income. What in the population mix is not a hot button? Especially when the word “control” is added, and when the world’s biggest religions have fruitful multiplication embedded in their philosophical DNA. And so critics from left, right and the intellectual center gang up on the handful of environmentalists and other activists who try to get population into national and global discussions.
Yet newly released population data from the U.N. show that developed countries, from the U.S. to Spain, have been experiencing (at least up through the beginnings of the economic crisis in 2008), if not baby booms, at least reproductive “rat-a-tat-tats.” For the first time since the 1970s, the average number of children born to U.S. women has topped 2.1—the number at which parents replace themselves in the populations of developed and many developing countries. Even if net immigration ended tomorrow, continuation of that fertility rate would guarantee further growth in U.S. population for decades to come.