Voluntary depopulation


During the first two weeks of December, delegates from around the world are meeting in Madrid for the latest round of international negotiations to address climate change. Although the Trump administration has stated its intention to withdraw from the historic 2015 Paris agreement, a congressional delegation led by House speaker Nancy Pelosi is attending the Madrid summit to “reaffirm the commitment of the American people,” according to a press release from her office. This raises an interesting question: If ordinary citizens are truly committed to battling climate change, what are the most effective actions that individuals can take?

A recent letter to the Boulder Weekly alluded to a 2017 article in Environmental Research Letters, in which sustainability scientists Seth Wynes and Kimberly Nicholas attempted to answer exactly this question. The study identified four lifestyle choices with the greatest climate impact: eating a plant-based diet, avoiding air travel, living car-free and having fewer children. Although the first three are unlikely to surprise most people, the final one is rarely discussed in relation to climate change. But in the U.S., where ecological footprints are relatively large, the long-term impact of reducing the birthrate is much greater than other lifestyle choices. Having one fewer child in the U.S. is roughly equivalent to 40 people living car-free, 80 people avoiding one transatlantic flight per year or 120 people going vegan.

To arrive at this conclusion, Wynes and Nicholas assumed that consumption patterns would remain the same in the future, and they divided the total climate impact of each child over the lifetimes of both parents. If national policy eventually changes the per-capita ecological footprint, the impact of having one fewer child might actually be lower. And because the benefits to the climate are spread over the lifetimes of the parents, the effects are less immediate than other lifestyle choices. The reality of the climate crisis is that immediate actions are needed to address current heat-trapping emissions, but additional reductions will also be needed in the future to avoid dangerous levels of warming.

“Those of us who want to step forward on climate need to know how our actions can have the greatest possible impact,” said lead author Seth Wynes, a Ph.D. student at the University of British Columbia in Canada. “This research is about helping people make more informed choices.”

So why do governments promote lower-impact actions like recycling when other lifestyle choices would have a much greater effect? The answer may be that economic growth has historically been connected to population growth. Without any real increases in productivity, the economy naturally grows with the population because more people buy more things. Trying to sustain economic growth without a growing population, whether by birth or by immigration, is difficult. Government programs like Social Security and Medicare depend on more workers today paying for the benefits of previous generations, who are now living longer than ever. And a national response to the climate crisis, like investing in renewable energy infrastructure, is also much easier in a growing economy.

Any talk of depopulation brings to mind China’s disastrous experiment with the one-child policy, which officially ended in 2015. In addition to creating a horrific gender imbalance for an entire generation, this policy continues to be a source of hardship for only-children, who are now trying to meet the cultural expectation of taking care of their parents. The lesson may be that any deliberate effort to depopulate in other countries should be voluntary rather than forced. To avoid disrupting family structures, efforts could focus on promoting childless living for most of the population, rather than one child for every family. 

If widely adopted in the U.S., voluntary depopulation could cut the average birthrate in half, potentially reducing the population (and heat-trapping emissions) by about 25% over 40 years. That’s not a solution to the climate crisis by itself, but it’s a much greater reduction than national policy has achieved so far.

“We recognize that these are deeply personal choices. But we can’t ignore the climate effect our lifestyle actually has,” said study coauthor Kimberly Nicholas, an associate professor at Lund University in Sweden. “It’s especially important for young people, establishing lifelong patterns, to be aware which choices have the biggest impact. We hope this information sparks discussion and empowers individuals.”

What can governments do to promote childless living among most of the population? To start, they could eliminate the tax exemption for children, replacing it with a tax credit for childless households and maybe even a per-child tax penalty for families with more than two kids. This goes against government interests, because it ensures fewer taxpayers in the future, but politicians must resist the temptation to continue providing incentives for population growth. Whatever per-capita reductions in heat-trapping emissions are possible over the coming decades, it is a mathematical certainty that future citizens can enjoy a better standard of living when there are fewer people on the planet.  

Travis Metcalfe, Ph.D., is a researcher and science communicator based in Boulder. The Lab Notes series is made possible in part by a research grant from the National Science Foundation.