Whether residents of high-income countries are morally obliged to have fewer children is a growing debate in climate ethics. Due to the high anticipated carbon impact of future population growth, some climate ethicists express support for non-coercive population engineering policies such as reduced child tax credits.
This debate has attracted widespread public attention, making family planning a key issue in climate change prevention.
Much of the debate is underpinned by one influential US study published in 2009 from Oregon State University. The premise of the study is that a person is responsible for the carbon emissions of their descendants, weighted by their relatedness. A grandparent is responsible for one quarter of each of their grandchildren’s emissions, and so on.
By having a child, a cycle of continued procreation over many generations is started. The emissions of future generations are included in the carbon legacy of their ancestors.
The carbon impact of children
Based on this logic, the authors found that having one child adds 9,441 tonnes of carbon dioxide to the carbon legacy of each parent. This equates to more than five times their own lifetime carbon emissions. The potential savings from reduced reproduction are therefore dramatic.
This result is usually taken at face value in both academic debates and popular discussions, while its details and assumptions are rarely scrutinised. Yet the result is contingent on the assumption that all future generations will indefinitely emit at 2005 levels, an assumption that now appears to be wide of the mark.
For example, from 2005–2019, before they were artificially suppressed by the COVID pandemic, US per-capita emissions fell by 21%. And they are likely to fall further in the future.
Large public investments are accelerating the transition towards carbon neutrality. The recent US Inflation Reduction Act allocated US$369 (£319) billion towards fighting climate change.
Reconsidering the carbon impact of children
Considering these efforts, the central assumptions underpinning the study need revisiting.
Using the same reasoning that yielded large carbon impact figures for procreation, we instead suggest that having a child today could be far less environmentally harmful than is widely considered.
If high per-capita emitting countries achieve net zero by 2050, then a child born in one of these countries in 2022 would generate emissions only until they are 28 years old. After 2050, they and their descendants would cease to cause any additional emissions. Adding up their lifetime emissions therefore yields a much lower carbon legacy.
Assuming emissions decrease linearly to zero until 2050, and that the child does not reproduce in that time, a child born in 2022 will add seven years of carbon emissions to each parent’s lifetime carbon footprint. This is because in the 28 years to 2050, a linear decrease can be modelled as half the total amount on average (14 years) with each parent responsible for half of their child’s footprint (seven years). Subsequent generations add zero emissions to this amount.
The difference between this potential scenario and the accepted “constant emissions” scenario is stark. Yet even this much lower result may still overestimate the carbon impact of having a child.
This figure assumes that a child will cause additional emissions at the per-capita rate of their country of residence. However, children typically engage in fewer high-emission activities than an adult. They share a household with their parents, and will not drive their own car or commute to work for much of the period before 2050.
Particularly in the immediate future, where per-capita emissions are at their highest, a child will likely cause far fewer emissions than their country’s per-person average.
Net zero commitments must be fulfilled
The pursuit of net zero can greatly reduce the climate impact of childbearing in countries with high per-capita carbon emissions. However, this remains dependent on the fulfilment of this commitment.
Progress towards net zero is stuttering, with current climate policy in many countries lagging behind their pledges.
Despite having a net zero strategy, the UK’s progress towards carbon neutrality has been limited. UK emissions rose 4% in 2021 as the economy began to recover from the pandemic – and many other high per-capita emitting countries are in a similar situation. Prime Minister Liz Truss’s cabinet appointments have also raised doubt over the UK’s commitment to climate targets.
So delivering emphatic reductions to the carbon impact of procreation remains distant, despite our reassessment of the 2008 study.
As a society, it is in our power to put ourselves on a credible net zero path. This also means rejecting the popular tendency to assume that climate change should be addressed by individual lifestyle adjustments, rather than by institutional and structural change. Should net zero be achieved, it would be possible to have children without being saddled with environmental guilt.