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Fertility and the environment, a tricky equation
This article is published in partnership with Dialogues économiques, produced by Aix-Marseille School of Economics(AMSE).
In France, as across much of the world, people are having fewer children. In 2025, 645,000 babies were born in the country – 24% fewer than in 2010, the most recent peak in births, according to France’s National Institute of Statistics and Economic Studies (Insee)1. The total fertility rate, which stood at 2.0 children per woman in 2014, fell to 1.56 in 2025, the lowest level since the end of the First World War.
This decline is evident across Europe, where the average fertility rate is around 1.4 children per woman, and more broadly across high-income countries, as well as an increasing number of middle-income nations. In France, people say they want fewer children – particularly those belonging to the younger generations – with a growing share saying they intend to have no children or just one. Over the past 20 years, the number of children under-30s say they would like to have has fallen by 0.6 on average: from 2.5 to 1.9 among women and from 2.3 to 1.8 among men.
France's population continued to grow slowly, by around 0.25%, and the country still recorded a positive natural increase in 2024, with roughly 17,000 more births than deaths. In 2025, however, natural change turned negative for the first time since the Second World War, with around 6,000 more deaths than births. Declining birth rates have now become a prominent concern in political discourse: in early 2024, President Emmanuel Macron called for a "demographic rearmament", presenting a revival in the birth rate as one of the pillars of France's national "power".
Anxiety: the enemy of fertility?
So, what lies behind the fall in fertility rates? The answer is of course multifaceted, but it appears to be linked to a range of unfavourable global conditions. A United Nations study investigating the barriers to having children across 14 countries2 found that respondents most often cited economic hardship: financial constraints (39%), unemployment or job insecurity (21%), housing problems (19%), and difficulties accessing childcare (12%). The unequal distribution of domestic work between women and men was also cited, by 13% of women and 8% of men.
Health-related issues also play a role, including chronic illness and infertility, cited by 12% of respondents. In France, nearly 15% of couples experience difficulties conceiving. The rising age at which women have their first child – now around 29 – as well as environmental pollution and limited access to medically-assisted reproduction can all affect fertility.
But that is not the whole story: if people are having and wanting fewer children, it is also because they are concerned about the future – whether socially, politically or environmentally. According to the French Institute for Demographic Studies (INED)3, 35% of people aged 25 to 39 who are very worried about the prospects facing future generations say they will “probably” or “certainly” have a child, or another child, compared with 46% among those who are less worried. The former also want, on average, 0.11 fewer children.
The economics of family and fertility
Paolo Melindi-Ghidi and Thomas Seegmuller, economists at Aix-Marseille School of Economics (AMSE), set out to investigate how pollution might affect fertility decisions4. Until now, economists have largely explained declining birth rates in wealthy countries by financial factors. “The economics of the family, building on the work of Nobel laureate Gary Becker, has explained this trend by the trade-offs people make between their personal preferences and the costs those preferences entail – in financial terms, as well as in terms of time and education,” explains Seegmuller.
People derive satisfaction from the choices they make within the limits imposed by their resources – in other words, “If a couple wants to have children, they weigh up their ambition against the costs. And those costs vary enormously from one country to another: raising a child in Manhattan, for example, is far more expensive than in a sub-Saharan African country.” In addition, “Research has also shown that as countries become more developed, people tend to invest more heavily in their children’s education. As a result, they choose to have fewer offspring,” he says. This is the economic relationship between ‘quality’ and ‘quantity’.
“This demographic transition has been observed in most advanced economies,” Melindi-Ghidi adds. “In the early stages of a country’s development, falling mortality rates lead to rapid population growth while birth rates remain high. Then, once a certain standard is reached, fertility rates begin to fall.”
A socioeconomic paradox
Yet when the two researchers compared data from different US states, they found that the correlation between a country’s fertility rates and pollution levels was at least as strong as the more familiar relationship between birth rates and economic development.
“We started with two observations,” says Seegmuller. “Firstly, studies in psychology and behavioural science have shown that environmental concerns are playing an increasingly important role in fertility decisions. Secondly, we found that in the US, states with the most carbon-intensive economies, such as Texas, also tend to have the highest fertility rates. Conversely, states such as California, where carbon intensity is lesser, generally have lower fertility rates.”
At first glance, the finding appears paradoxical: one might expect those living in the most polluted states to be more reluctant to have children. “People’s ecological concerns are closely related to the degree of environmental degradation, particularly the carbon intensity of the economy – that is, the amount of carbon dioxide (CO₂) emissions generated per unit of gross domestic product (GDP). But we found that the less pollution there is, the more citizens tend to support stronger environmental regulations. Conversely, when carbon intensity is high, more people believe that such regulations are detrimental to jobs and the economy.”
In summary, the lower the carbon intensity, the stronger people’s environmental concerns. “That came as a surprise,” Seegmuller admits. “Our aim then became to put forward an economic explanation that could account for this finding.”
Conflicting sources of satisfaction
On this basis, the researchers added an environmental dimension to the traditional quality-versus-quantity framework: an environmental index measuring the ratio between the production of green goods – electric vehicles, renewable energy and so on – and that of polluting goods, such as conventional combustion-engine cars. The greater the share of green production, the higher the environmental index and the lower the economy’s carbon intensity. The index captures the value households attach to environmental quality when making decisions. In other words, it becomes another factor in the trade-offs they make, alongside their assessment of financial and other costs.
“One of the key points of our model is to show that this has a direct impact on the decision about how many children to have – but, more importantly, that these variables cannot be separated.” In a conventional economic model, the number of children and the state of the environment can be treated independently: people are happy to have offspring, and besides, derive pleasure from living in a high-quality environment. Here, however, the satisfaction associated with having children also depends on the quality of the environment.
“Another key contribution of our research is the idea that preferences for the number of children and environmental concerns can either complement or replace one another. The most interesting results emerge when the two sources of satisfaction are substitutable,” Melindi-Ghidi points out. “The reasoning is as follows: a less carbon-intensive economy is associated with stronger ecological concerns and better environmental quality. If this improvement in environmental conditions is a replacement for having children in people’s preferences, then the number of offspring they want decreases.” In other words, Seegmuller adds, “I’m going to have fewer children because I’m already happy that the environment is improving.”
There is, however, another aspect to the relationship between population and the environment: the more people there are, the more pollution – unless Earth dwellers fundamentally change the way they live and consume. “According to the economic literature about the effects of demographic growth on environmental degradation, a declining population might, in fact, not be a bad thing,” Seegmuller concludes. Birth rates and the environment, it seems, are an equation with no simple solution.
- 1. See: https ://www.insee.fr/en/statistiques/8726555
- 2. See: https://www.unfpa.org/swp2025
- 3. See: https://www.ined.fr/en/publications/editions/population-and-societies/pe...
- 4. P. Melindi-Ghidi et T. Seegmuller, “The Dynamics of Fertility Under Environmental Concerns”: http://dx.doi.org/10.2139/ssrn.4744985
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"Stéphanie Arc is a scientific journalist who regularly contributes to CNRSLejournal. She also holds a degree in philosophy and is a published author and specialist of gender issues and sexuality. She has recently pulished Identités lesbiennes. En finir avec les idées reçues (Paris : éditions du Cavalier bleu, 2015). Today, her research focuses on lesbian history, culture and...