The rise in population since 1900 has been so rapid that up to 14% of all humans that have ever lived are still alive today, according to recent research.

Other research shows that slowing population growth could provide between 16% and 29% of emissions reductions necessary by 2050 to avoid the effects of dangerous climate change, concluding “reduced population growth could make a significant contribution to global emissions reductions”.

In a previous article, we argued that a decision to have children or not could be a vital part of climate policy, perhaps through a market-based mechanism similar to emissions trading.

But a new paper casts doubt on our ability to make any meaningful dent in population growth.

Corey Bradshaw and Barry Brook at the University of Adelaide argue in Proceedings of the National Academy of Sciences that the even a global one-child policy, or the catastrophic death of billions of people, would not slow population growth enough to reduce carbon emissions and resource use.

So, is it time to put market-based population control to bed?

More kids, more carbon

The UN forecasts that by 2100 there may be 10.9 billion people on Earth. If families, on average, have half a child more than the UN projects, population could reach 16 billion by 2100.

If you have two children, your carbon legacy could be forty times higher than any savings you make.

Market-based mechanisms — emissions trading schemes — are ubiquitous around the world at the national, state or region and local levels to address the climate change problem, to mitigate the effects of climate change.

So it’s no surprise that some experts have drawn on them to solve the population problem.

Emissions trading the policy of choice

When it comes to mitigating the effects of climate change, the question is whether to rely on quantity-based or price-based instruments.

A quantity-based instrument is an ETS, the most common example of which is a cap-and-trade scheme — what the former Australian Carbon Pricing Mechanism would have become this year, for instance. A price-based instrument is a carbon tax.

An ETS is the instrument of choice around the world — for developed and developing states — to address the climate change problem. It is a market-based instrument under which limits are placed on the quantity of carbon that can be emitted.

There are two broad, alternative types of emissions trading schemes, “cap and trade” and “baseline and credit”. The latter model is not widely used.

Under the cap and trade model, the scheme sets a maximum quantity of emissions for a compliance period (a year, for example), across the whole sector to which the scheme applies.

Permits are issued by the scheme administrator totalling that cap. An emitter must obtain and surrender to the scheme administrator at the end of the compliance period a permit for each unit of its emissions during the compliance period. The initial issue of permits may be allocated free of charge or auctioned.

Cap and trade schemes exist, in one form or another, and in various stages in the European Union, India, China, Kazakhstan, South Korea (next year), New Zealand, California, Quebec (which links with the California ETS) nine US northeastern and mid-Atlantic states (the Regional Greenhouse Gas Initiative), and Tokyo.

An emissions trading scheme is the global climate change policy of choice.

Procreation permits?

There’s not much these days that money can’t buy. We live in a time when almost everything can be bought and sold.

As Michael Sandel, a professor of politics at Harvard University, notes: “the logic of buying and selling no longer applies to material goods alone. It increasingly governs the whole of life”.

You could argue that we live in a society where everything is up for sale.

Recently, New York Times reporter Andrew Revkin asked if it is far fetched for individuals to be compensated for having fewer or no children.

At a Wilson Center discussion in 2009, Revkin wondered whether the next step, in a world enamoured with carbon markets, would be carbon credits for avoided children:

Should you get credit — if we’re going to become carbon-centric — for having a one-child family when you could have had two or three? And obviously it’s just a thought experiment, but…

A thought experiment

Market-based population control is a thought experiment with its origins with the economist Kenneth Boulding in 1964.

Boulding proposed a system of marketable procreation licenses as a way of dealing with overpopulation:

I think … that a system of marketable licenses to have children is the only one which will combine the minimum of social control necessary to the solution to this problem with a maximum of individual liberty and ethical choice. Each girl on approaching maturity would be presented with a certificate which will entitle its owner to have a certain number of children.

Boulding suggested that a market would then be set up in these units “in which the rich … would purchase them from the poor, the mums, the maiden aunts, and so on”. Others assessed Boulding’s proposal and proposed amendments.

The Boulding proposal was revived by two Belgian academics in 2006. They pointed out that, since the rich would likely buy procreation licenses from the poor, their scheme would have the further advantage of reducing inequality by giving the poor a new source of income.

And in 2007, Perth-based medical academic Barry Walters proposed a “baby levy” in the form of a carbon tax in line with the “polluter pays” principle. Every family choosing to have more than a defined number of children should be charged a carbon tax that would fund the planting of enough trees to offset the carbon cost generated by a new human being.

Sandel argued, however, in light of such proposals, that notwithstanding an argument that a market in children (or in the right to have them) might be efficient, “trafficking in the right to procreate promotes a mercenary attitude toward children that corrupts parenthood”.

Is population control the solution?

But all of this may be irrelevant in light of the important research conducted by Bradshaw and Brook. Their research shows that:

No matter what levers you pull, we have such a huge demographic momentum, there’s no way we can rein in the human population fast enough to address sustainability issues in the next century.

Population growth trends for the rest of the 21^st Century are “virtually locked-in” unless there are “extreme and rapid reductions in female fertility”.

Even a global one-child policy and the catastrophic death of several billion people, they argued, would not materially affect CO₂ emissions and resource use; the result would still be 5 to 10 billion people by 2100.

The authors of the research ultimately conclude that “there are no easy ways to change the broad trends of human population size this century”.

So, while market-based population control might encourage people to have fewer children, when it comes to addressing the twin problems of climate change and overpopulation it may be better to simply concentrate our trading schemes on climate change.