Our Slice of the Carbon Cycle: A Numbers Game

by Alex Taylor

Photo: Sao Paulo at night by Julio Boaro

At the dawn of the modern environmentalist movement, as we awoke to the devastating downsides of modern industrial life, our first and most obvious response was to cut back. If our voracious consumption of Earth’s bounty was hurting the environment, the thinking went, then we should probably trim that consumption.

That logic is still sound. Reducing the amount of land and energy we appropriate from nature – cutting our share of the global carbon cycle – is still a surefire way to relieve overtaxed ecosystems. Less consumption means fewer acres plowed under for agriculture or paved over for factories and malls. That means more acres of wild habitat, which means your grandkids stand a chance of someday taking their children for a nature walk.

There are basically two ways to trim consumption: cut the amount each person consumes, or reduce the total number of people.  As our world becomes both richer and more populated, achieving either of these can sometimes seem impossible without resorting to politically extreme measures like forced rationing or China’s one-child policy. Reigning in worldwide consumption is indeed a daunting challenge, and one we will save for the next installment of this series. On the population front, however, we are beginning to see encouraging signs that the problem may be working itself out naturally.

Crowded Earth

While all babies are precious and adorable little miracles, we may be getting too much of a good thing. Each person needs food, a place to sleep, and hopefully a little something extra to make it all worthwhile. As Thomas Malthus gloomily noted as far back as the late 1700’s, the more people there are, the harder it is to sustainably share limited resources. He was thinking about the threat of famine and war, but overpopulation also taxes the Earth’s resources. While the focus of this series is the latter set of problems, the former remain a relevant concern, as a world of dwindling resources will get nasty quickly.

Technological patches like the Green Revolution in agriculture, as well as an expansion of land under plow, have for the most part kept food production in line with population since the time of Malthus’ predictions. Though there are several promising social and technological solutions in the pipeline, there is no guarantee that these fixes will continue to fill the gap between supply and demand as we draw on Earth’s resources unsustainably and at a level unprecedented in history. Reducing the number of humans on Earth is critical to avoiding both environmental destruction and political unrest.

Fortunately, though the total number of humans is still rapidly increasing with an average net gain of two people per second, the rate of population growth is slowing. While we are still driving towards a cliff, at least our foot is off the accelerator.

Comic Market

We are many. Photo: Kobak

Any meaningful reduction in human consumption is going to require changes in both top-down policy and bottom-up culture. Top-down international efforts to disseminate birth control and sex education have had some success in reducing fertility in the developing world. More draconian measures like China’s one-child policy have also proven effective in reducing birth rates, though this solution is unlikely to appeal to less totalitarian societies. However, government rules on childbirth are particularly odious political waters, impinging on our most basic human rights and bringing up memories of sterilization campaigns.

Thankfully, the worldwide slowdown in population growth is overwhelmingly due to bottom-up cultural and economic change, not top-down policy. Fertility tends to drop as countries industrialize and become wealthier. One major reason touted by economists is the shift in incentives for parents as the job market changes. In very poor areas, where education is unavailable and children are at risk of dying young, having many children is a kind of retirement plan, since young children can work the fields and adult children can support their parents in old age. As a country moves up the income scale, jobs require more education, public health improves, and national safety nets strengthen. Investing in educating fewer children becomes a better bet for many parents who are fortunate enough to make it into the emerging middle class.

Family in Orissa

How many more children? Source: UK Dept. of International Development

Economic incentives aren’t the only drivers of something as intensely personal and human as childbearing, of course. Factors like culture, sex education, access to birth control, and gender norms also play a role. Feminists like Margaret Sanger were some of the earliest pioneers of modern family planning, and helping women take control of their reproductive rights remains an important battleground for both social justice and environmentalism. Without these rights and modern birth control (a term coined by Sanger), the economics wouldn’t matter because people wouldn’t have the means to plan their families.

The natural drop in the population growth rate is perhaps the most promising signs that we might be able to get global human consumption to sustainable levels, without resorting to unjust, politically extreme solutions. While the population growth rate is slowing down, we still have to find a way to provide for the estimated 9.6 billion people who will be alive by 2050 without overtaxing the Earth’s resources. Ironically, the very same globalizing and enriching forces that are pushing down fertility rates across the globe are stoking per capita consumption, pushing us further away from sustainability.

Reducing our appropriation of Earth’s resources to a sustainable level in a timely and just way is an enormous and unprecedented global challenge. It will require deep cooperation across nations with very different political systems, combining top-down and bottom-up, political, cultural and technological solutions. There’s no guarantee that we will succeed, but we have to try.

In the next installment of this series, we will explore some of the tools we have at our disposal to reduce each person’s environmental impact while allowing for a decent and respectable life for the people of this planet.


Debpuur, Cornelius, et al. “The impact of the Navrongo Project on contraceptive knowledge and use, reproductive preferences, and fertility.” Studies in family planning 33.2 (2002): 141-164. link

Hesketh, Therese, Li Lu, and Zhu Wei Xing. “The effect of China’s one-child family policy after 25 years.” New England Journal of Medicine 353.11 (2005): 1171-1176. DOI

McDonald, Peter. “Gender equity in theories of fertility transition.” Population and development review 26.3 (2000): 427-439.  link

Moav, Omer. “Cheap Children and the Persistence of Poverty*.” The Economic Journal 115.500 (2005): 88-110. link