Children are expensive – not just for parents, but the environment – so how many is too many?

People born in the future stand to inherit a planet in the midst of a global ecological crisis. Natural habitats are being decimated, the world is growing hotter, and scientists fear we are experiencing the sixth mass extinction event in Earth’s history.

Under such circumstances, is it reasonable to bring a child into the world?

My philosophical research deals with environmental and procreative ethics – the ethics of choosing how many children to have or whether to have them at all. Recently, my work has explored questions where these two fields intersect, such as how climate change should affect decision-making about having a family.

Procreation is often viewed as a personal or private choice that should not be scrutinized. However, it is a choice that affects others: the parents, the children themselves and the people who will inhabit the world alongside those children in the future. Thus, it is an appropriate topic for moral reflection.

A lifelong footprint

Let’s start by thinking about why it might be wrong to have a large family.

Many people who care about the environment believe they are obligated to try to reduce their impact: driving fuel-efficient vehicles, recycling and purchasing food locally, for example.

But the decision to have a child – to create another person who will most likely adopt a similar Lifestyle to your own – vastly outweighs the impact of these activities. Based on the average distance a car Travels each year, people in developed countries can save the equivalent of 2.4 metric tons of CO2 emissions each year by living without a vehicle, according to one literature review. For comparison, having one fewer child saves 58.6 metric tons each year.

So, if you think you are obligated to do other activities to reduce your impact on the environment, you should limit your family size, too.

In response, however, some people may argue that adding a single person to a planet of 8 billion cannot make a meaningful difference. According to this argument, one new person would constitute such a tiny percentage of the overall contribution to climate change and other environmental problems that the impact would be morally negligible.

Crunching the numbers

Environmental ethicists debate how to quantify an individual’s impact on the environment, especially their lifetime carbon emissions.

For example, statistician Paul Murtaugh and scientist Michael Schlax attempted to estimate the “carbon legacy” tied to a couple’s choice to procreate. They estimated the total lifetime emissions of individuals living in the world’s most populous 11 countries. They also assumed a parent was responsible for all emissions tied to their genetic lineage: all of their own emissions, half their children’s emissions, one-quarter of their grandchildren’s emissions, and so on.

If emissions stayed similar to 2005 levels for several generations, an American couple having one fewer child would save 9,441 metric tons of CO2-equivalent, according to their calculations. Driving a more fuel-efficient car, on the other hand – getting 10 more miles to the gallon – would save only 148 metric tons of CO2-equivalent.

Philosopher John Nolt has attempted to estimate how much harm the average American causes over their lifetime in terms of greenhouse gas emissions. He found that the average American contributes roughly one two-billionth of the total greenhouse gases that cause climate change. But since climate change may harm billions of people over the next millennium, this person may be responsible for the severe suffering, or even death, of one or two future people.

Collective toll

Such estimates are, at best, imprecise. Nevertheless, even if one assumes that each individual child’s impact on the environment is relatively insignificant on the global scale, that does not necessarily mean that procreators are off the moral hook.

One common thought in ethics is that people should avoid participating in enterprises that involve collective wrongdoing. In other words, we should avoid contributing to institutions and practices that cause bad outcomes, even if our own individual contribution to that outcome is tiny.

Suppose someone considers making a small donation to an organization that they learn is engaged in immoral activities, such as polluting a local river. Even if the potential donation is only a few dollars – too small to make any difference to the organization’s operations – that money would express a degree of complicity in that behavior, or perhaps even an endorsement. The morally right thing to do is avoid supporting the organization when possible.

We could reason the same way about procreation: Overpopulation is a collective problem that is degrading the environment and causing harm, so individuals should reduce their contribution to it when they can.

Moral gray zone

But perhaps having children warrants an exception. Parenthood is often a crucial part of people’s life plans and makes their lives far more meaningful, even if it does come at a cost to the planet. Some people believe reproductive freedom is so important that no one should feel moral pressure to restrict the size of their family.

One point of general consensus among ethicists, following the lead of philosopher Henry Shue, is that there is a moral difference between emissions tied to crucial interests and those that are tied to convenience and luxury. Emissions connected to basic human needs are usually regarded as permissible. It isn’t wrong for me to emit carbon to drive to the grocery store, for example, if I have no other safe or reliable transportation available. Getting to the store is important to my survival and well-being. Driving purely for recreation, in contrast, is harder to justify.

Reproduction occupies the messy conceptual space between these two activities. For most people today, having their own biological children is not essential to health or survival. Yet it is also far more important to most people and their broader life plans than a frivolous joyride. Is there a way to balance the varied and competing moral considerations in play here?

In prior work, I have argued the proper way to balance these competing moral considerations is for each couple to have no more than two biological children. I believe this allows a couple an appropriate amount of reproductive freedom while also recognizing the moral significance of the environmental problems linked to population growth.

Some authors reason about this issue differently, though. Philosopher Sarah Conly argues that it is permissible for couples to have only one biological child. In large part, her position rests on her argument that all the fundamental interests tied to child-rearing can be satisfied with just one child. Bioethicist Travis Reider argues in favor of having a small family, but without a specific numerical limit. It is also possible, as ethicist Kalle Grill has argued, that none of these positions gets the moral calculus exactly right.

Regardless, it is clear that prospective parents should reflect on the moral dimensions of procreation and its importance to their life plans.

For some, adoption may be the best way of experiencing parenthood without creating a new person. And there are many other ways for prospective parents to do their part in mitigating environmental problems. Carbon offsets or donations to environmental organizations, for example, are hardly perfect substitutes for limiting procreation – but they certainly may be more appealing to many prospective parents.