A growing mountain of reports highlights one of the US’s most fascinating features: the fact that people in red states seem to breed far more than those in the blue ones, and are being newly encouraged to do so by high-profile figures who are desperate for a Maga baby boom. The vice-president, JD Vance, and his wife are expecting their fourth child, and Vance says he wants “more babies in America” – and, presumably, fewer of the people he derided as “childless cat ladies”. Elon Musk is reckoned to be a father of 14, and his views on reproduction reflect his contribution to the Trumpist procreation drive: “If people don’t have more children, civilisation is going to crumble,” he said in 2021. “Mark my words.”

In Europe, Italy’s far-right prime minister, Giorgia Meloni, says she will somehow tackle a mixture of unprecedentedly low birthrates and ageing population known as the “demographic winter”. Before he was sent packing by voters, the infamous Viktor Orbán was on much the same page: “We need Hungarian children,” he said in 2019, announcing a lifelong exemption from income tax for women with four or more of them.

Such is yet another front in the world’s seemingly ceaseless culture war. Though it is far from the truth, falling birthrates are blamed on rampant liberal individualism, and comfortably off women who dare to want meaningful working lives. Clearly, the issue also plays directly into the new right’s consuming obsession with immigration, as well as highlighting the familiar insistence that however much the Earth burns, people and corporations should carry on doing what they damn well want.

On the face of it, all this might suggest that progressives should insist that falling birthrates are nothing but a good thing, and not just because they represent one of the most fundamental kinds of women’s liberation. Thousands of people have already taken that stance as a matter of personal choice, backed by climate research: in 2017, one landmark study claimed that having one fewer child resulted in a reduction of carbon emissions amounting to 58.6 tonnes for each year of a parent’s life, dwarfing such lifestyle changes as eating a meat-free diet (which saved 0.82 tonnes of CO2 a year) and living car-free (2.4 tonnes). Then again, there are now plenty of voices who insist that the ecological benefits of falling birthrates simply take too much time to materialise: to quote one academic paper from the US, “Low fertility is a false solution to climate change: the population impacts are too small and too slow.”

There are other, rather less scientific arguments against the idea that fewer births will necessarily help the fight against global heating. One was voiced last year by the academic David Runciman, who nailed the big problem with democratic societies low on younger voters: “Ageing societies vote differently, consume differently and invest differently from more balanced societies … A falling birthrate makes thinking about the future harder because it means a greater share of resources being directed towards the needs of people who have already lived most of their lives … it threatens to distract our attention from the other things that matter.”

It really does. Moreover, as the proportion of older people increases, the state has to deal with fewer workers supporting ever-rising spending on pensions, health and social care. That will mean less money for climate action and mitigation – and governments that simply cannot afford to take the long view of anything.

Meanwhile, huge social shifts gain pace. Last week, amid such pull-quotes and headlines as “It’s not a nice world to bring children into”, it was announced that England and Wales’s total fertility rate – the average number of children a woman is expected to have in her lifetime – had fallen to just under 1.4, marking the fourth consecutive year of decline and the lowest figure in nearly 50 years. In the year to mid-2023, deaths in the UK outstripped births, also for the first time in half a century. Schools are running with thousands of surplus places (Southampton, for example, is forecasting 3,000 in 2029-30, equivalent to 100 classes), and looking into a future in which mass closures will become inevitable. More child-focused businesses will fold. Eventually, towns and villages may start to hollow out. The country may start to feel quiet, staid and uptight: there may even be a slow rewinding of our embrace of all things family-friendly.

With the exception of sub-Saharan Africa, much the same trends now run across high-, middle- and low-income countries and regions of the world. Despite a couple of recent upticks, South Korea remains right at the bottom of the global birthrate rankings, thanks to – among other things – the impossible costs of housing and childcare. Last year, a New Yorker article headlined The End Of Children quoted an anonymous resident of Seoul who worked as a journalist, and was killing time in a cafe that was completely silent. “People hate kids here,” she said. “They see kids and say, ‘Ugh.’ People call moms ‘bugs’ or ‘parasites’. If your kids make a little noise, someone will glare at you.”

What is causing all this? The answer boils down to an uneasy mixture of social progress (witness widespread falls in teenage pregnancies) and emancipation, and the more shadowy features of modern capitalism: insufficient social housing, expensive childcare, insecure and low-paid work, and a general pessimism about the future. The American writer Anna Louie Sussman is about to publish a book titled Inconceivable: The Impossibility of Family in an Age of Uncertainty. She is one of many voices who see the decisive start of the modern fertility drop in the crash of 2007-8, and “its status as the first economic crisis of the era of nonstop digital information deluge, which rendered it, and the sense of dread it engendered, all but inescapable, even for people not financially affected”.

She also points out that, contrary to the idea of falling birthrates being a matter of middle-class decadence, between 2007 and 2016, falling fertility rates in the US followed a steeper curve among US women without college degrees, whose births dropped 12% below projections; whereas among female graduates, births dropped by just 7%. This is a difference evident in many other countries.

Thanks chiefly to the rising popularity of Reform UK, British people will soon be hearing much more about birthrates. “We’re trying to cut immigration drastically,” a party spokesperson said last summer. “At the same time, to fix that population crisis, we’re trying to encourage British people already here to have kids.” This explains the Reform leader Nigel Farage’s plan to bring in new tax breaks for married couples, and his obnoxious suggestion that only “British-born” families should have the two-child benefit limit lifted.

Evidence from around the globe actually suggests that such tinkering has little effect. In fact, whether Farage, Vance, Meloni et al like it or not, what falling birthrates most vividly point to is a future in which immigrants will not be endlessly maligned by shameless politicians, but frantically competed for by countries that will fall into social breakdown without them. A lot of the people so enthusiastically backing the new right will surely experience this directly – and soon – in care homes and hospitals. There, they will be looked after by exactly the people their favourite leaders once demonised, who will be in ever shorter supply: a situation that already exists, but will soon become much more trying. At that point, we may witness a mass realisation far too late: that pulling up the drawbridge as birthrates crashed is the absolute definition of folly.

• John Harris is a Guardian columnist

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