EUROPEAN countries are buffeted by two global forces: atmospheric pressures that, as it were, change the weather, silently transforming societies and the assumptions of public policy. One is climate change (a change in the weather literally). The other is demography.

The two have a lot in common. Both are easily recognised but less easily understood. Both are products of complex forces and unobtrusive influences. Both create huge effects from minuscule changes. A rise in global temperature by one degree or a fall in fertility by one point may sound trivial but, over 100 years, will make the earth unbearably hot, or reshape the size and composition of societies.

Yet though every rich country has a climate-change policy, few have a population one (there are historical reasons for that). And just as everyone whinges about the weather, but does nothing about it, so everyone in Europe complains, but does nothing, about population. This article will argue that pessimism is no longer justified. It would be too much to say Europe's population is bouncing back. But its long-term decline is starting to bottom out, and is even rising in a few places.

On its face, this seems an odd assertion. In 1957, the year of the European Union's founding Treaty of Rome, every one of the 27 countries that are now EU members had fertility rates above 2.1 Now, none does. (The fertility rate is the number of children a woman can expect during her lifetime; 2.1 is the replacement level, the point at which the population stabilises.)

Received opinion holds, in the phrase of Auguste Comte, a 19th-century social scientist, that “demography is destiny” and that Europe is doomed by its death-spiral population numbers. American observers from Walter Laqueur, an academic, to Mark Steyn, a conservative polemicist, argue that Europe is fast becoming a barren, ageing, enfeebled place. Vast numbers of old people, they reckon, will be looked after, or neglected, by too few economically active adults, supplemented by restless crowds of migrants. The combination of low fertility, longer life and mass immigration will put intolerable pressure on public health, pensions and social services, leading (probably) to upheaval.

There are several possible objections to that gloomy forecast. One is that a growing population is not, of itself, necessarily a good thing, nor a falling one unambiguously bad. Another is that there is no short-term correlation between population change and wealth: Japan and South Korea have even lower fertility than Europe. But there is a simpler objection: the picture of relentless decline is wrong, or, to be accurate, half wrong. Europe is not in decline. Rather, as Jitka Rychtarikova of the Charles University in Prague argues, it no longer makes sense to talk about Europe as a single demographic unit at all. There are two Europes.

One is the familiar place of low fertility and population decline. Here, the fertility rate is below 1.5 and countries are struggling in a fertility trap. The low fertility belt runs from the Mediterranean to central and eastern Europe, embracing both old and new parts of the continent. The other, surprising Europe is a place of recovering fertility and rising population. It stretches from Scandinavia to France. Here, countries have escaped the fertility trap and the childbearing rate is around 1.8—not high, but higher than it was, and, in some cases, reaching the magic replacement level.

There is nothing odd in countries having different population patterns: you would expect that. But it is odd that countries should clump together into two broad clusters. That needs explaining.

In the decades after the second world war, rich countries everywhere experienced broadly similar trends. The bonds of traditional family life began to slacken. More women got jobs. People sought enjoyment and satisfaction more and more through individual pursuits, rather than in families. This social transformation, which also occurred in America and East Asia, led to a demographic bonus (a bulge of people in work) and to what might be called the postponement of everything. People left school later, left home later, married later, had children later. They also died later.

Low, low fertility Europe

The transition happened throughout Europe, but proceeded at different speeds in different places. In Scandinavia and the north-west it was gradual and consistent. In the Mediterranean and central-eastern Europe, it was a stop-start affair. There the Catholic church, buttressed by military dictatorships, kept “strong family” traditions alive. It encouraged marriage and children, and frowned on illegitimacy and women at work. This slowed the transition down. Then, when the dictatorships collapsed (or, in Italy, when post-war politics unravelled), the transition occurred in a rush as countries stampeded towards modernity. They became democratic and richer. They saw their cultural life flourish. And a generation of women started postponing childbirth. Fertility fell below 1.3 in Italy and Greece. The demographic bonus became a demographic onus.

Post-communist countries in eastern and central Europe reached the same point by a different route. Under communism, factories often provided free child care and higher salaries for parents with big families. But when communism collapsed, such policies disappeared. Combined with economic uncertainty, this sent post-communist nations tumbling into uncharted territory, with fertility rates falling even more precipitously than they had in the Mediterranean.

But that is not the end of the story. It explains why fewer children were born at a particular time, but not why childbearing stayed low. After all, there is no obvious reason why parents should choose to have only one child just because the Berlin Wall has come down. Events with a huge political significance may be, in demographic terms, just blips from which countries will recover sooner or later.

It is still possible that will happen. Women who were 20 when the wall fell have not yet reached the end of their child-bearing years. Perhaps birth rates will bounce back. But do not bet on it.

Germany not only has low fertility now, but has had for more than a generation. This suggests that “exceptionally” low rates can persist for decades. Admittedly, points out Michael Teitelbaum of the Sloan School in New York, Germany may simply be odd demographically. It also had low fertility in the 1920s, when few others did. But there are other reasons for doubting the “bounce back” thesis.

Women in their teens at the time of political transformation in Mediterranean countries are at the end of their child-bearing years. Their fertility rates have risen, but only slightly. There is little sign they produced a mini baby boom late in life.

Italy has no more childless women than France and Sweden, countries with much higher fertility rates (see table). But more Italian mothers have just one child. The pattern is still more marked in Russia, where a third of mothers have a single child. One possible explanation is that, squeezed between family obligations from the past and current social arrangements which limit job flexibility or cheap child care, many Italian and Russian women are reacting by satisfying social pressures to produce a family to the smallest possible extent—by having one child. Such a reaction may be hard to change.

There are also some signs that women in Europe may be having fewer children than they want. A survey by Eurobarometer, the EU's pollsters, for example, found that women who had finished bringing up their families said they had wanted (on average) 2.3 children. But they actually had only 2.1. Perhaps they were not answering truthfully. But the evidence does suggest there is a mismatch between desired and actual fertility.

The implications of that are worrying. Ms Rychtarikova suggests women are postponing, and postponing, and postponing—then finding it is too late to have more children. This could be for medical, socio-economic, or personal reasons. But whatever the cause, it seems to mean fertility rates can overshoot downwards.

When that happens, you can get new social norms: a one-child, or no-child policy by example. In Germany over a quarter of young women are childless, an exceptionally high number. One study showed that, on average, the number of children German women want is just 1.75, far below the replacement level. Another found that a fifth of young German women (and even more young men) say that having no children is fine. This is a sharp contrast with almost all previous surveys, which showed the ideal of the two-child family persisted regardless of what was actually happening in the country. After two generations, it seems, young Germans have given up the unequal struggle to keep the two-child ideal alive.

In other words, very-low-fertility countries can fall into a trap. Women defer children in response to one-off changes. Fertility rates fall. Deferrals go on longer than expected. Fertility undershoots. This changes social norms and you get new family patterns: lots of one-child families in Italy or Russia; exceptional numbers of childless adults in Germany.

Liberty, fraternity, fecundity

But countries are not doomed to fall into this trap. Over the past few years, almost a dozen places have not only avoided it, but begun to reverse their decline. France is leading the way.

Last July the French statistical office announced new population projections. France's population, it said, would grow by 9m from 2005 to 2050, when it would level off at 70m. At that point, assuming Germany's population continues to fall, France would become the most populous country in western Europe.

If that occurred, it would mark an historic recovery. France was the largest country in Europe up to the time of Napoleon, when it contained about a fifth of all Europeans and was the world's third-most-populous nation. The forecast growth would therefore negate 200 years of French paranoia about its more numerous eastern neighbour. Since European integration has been spurred, on the French side, by this fear, France's demographic recovery could have profound political implications for Europe.

France is one of three EU countries with a fertility rate above the magic replacement level (Denmark and Ireland are the others). It is natural to assume that this is because France also has many Muslim immigrants and Muslims have large families. Because France does not collect official statistics by religion, it is hard to know whether that assumption is accurate. But the country does register the birthplace of parents, so that one can calculate the family size of immigrants; and on the face of it, a study by Laurent Toulemon of the Institut national d'études démographiques appears to confirm the assumption. He found that immigrant women do indeed have high fertility: 2.5 compared with 1.65 for French-born women. But because immigrants make up only one-twelfth of women of childbearing age, this raises the national fertility rate only slightly.

However, Mr Toulemon also found that immigrants have a peculiar demographic profile: they are much more likely to have a baby during the first year or two after arriving in France than later. Young women, it seems, are waiting to conceive until they get to France. If you adjust their lifetime fertility rate to take account of this bulge of babies on arrival, you find immigrant fertility is about 2.2, not much above average. Immigrants are not pushing up the birth rate as much as they seem to be.

It is still possible that second- and third-generation Muslims (ie, those born in France) account for a disproportionate share of the country's high fertility. It is also possible that even if immigrants in France are not responsible for a higher birth rate, they are in other countries (Britain recently reported that 21.9% of births in 2005 were to mothers born outside Britain, compared with just 12.8% in 1996). Still, the evidence for all this is patchy; and it does not suggest that immigrants are responsible for a particularly large part of the overall fertility rise, in France at least.

Of course, like Germany, France is demographically unusual. It was the first country in the world to experience long-term population decline, starting in the late 18th century. Had it maintained the same birth rate as Britain since 1800, France would today have 150m people, surpassing Russia. The French have also long supported government policies to encourage more children, which other Europeans have rejected (perhaps because the Nazis were keen on them). The government still hands out medals for large families. French culture, the argument runs, is a good thing, so the more French people there are, the better.

But France is not unique. Official forecasts predict Britain's population will rise 15% by 2050, an extra 9m people. For Sweden, the forecasts say the population will grow by about a fifth. Some of this is the result of immigration and rising longevity but, according to David Coleman, a demographer at Oxford University, the recovery is also the result of older women having more children “almost sufficient to compensate for the sharply reduced birth rates of younger women”. This is exactly what was hoped for, but does not seem to be happening yet, in the Mediterranean and eastern Europe.

If you take account of late childbearing, you find that 16 European countries, with a total population of 234m, now have fertility rates of 1.8 or more. Half are above 2.0. Despite near-panic about “inevitably” declining population, then, some European countries are growing quite strongly. They are rare examples of bucking the trend that, as countries get richer, their birth rates fall.

Why? There are no obvious answers. The French run policies to increase the birth rate; the British do not. Most high-fertility countries are high-tax, high-welfare ones (France, the Netherlands, Scandinavia). But so is Germany, and its fertility has been declining for decades; whereas Ireland is not, and its population is growing. Maybe Ireland and France are responding to Catholic teaching on big families? Hardly. Remember Italy and Poland.

Though it is hard to be sure, the most plausible explanation is that some countries have struck a successful balance between life and work that enables parents to raise children without sacrificing their careers, and that this encourages child-rearing. If the explanation is right, it does not matter that France doles out presidential medals. But it does matter that it has an excellent, state-subsidised system of creches, to which mothers are happy to entrust their offspring.

Nor is it just a matter of guaranteeing minimum parental leave—or Germany, with generous provisions, would have lots of babies. Rather, the evidence suggests a whole host of measures, often designed to achieve other social goals, can boost the birth rate almost as a side-effect. These measures include a flexible education system (so parents can go back to school after having children); flexible working hours and, if Scandinavia is anything to go by, a strong emphasis on sexual equality.

This involves a shift of values as much as a change of policies. Northern countries have removed the stigma from illegitimacy (France stopped using the term in official documents in 2005; 55% of births in Sweden are outside wedlock). By and large, Mediterranean countries have not, and nor have Muslims in Europe. High-fertility countries do not merely tolerate mothers with paid employment; they encourage them to return to work and insist employers keep jobs open.

Go forth and multiply (a bit)

None of this means that Europe has broken the chains of its demography. The EU's overall population will fall by 7m by 2050. The so-called support ratio (roughly, the proportion of workers to pensioners) is declining everywhere. And as Mr Coleman points out, Europe's share of global population will fall from 21% now to 7% by 2050. Even its successes are only relative. A fertility rate of 1.8 is still below replacement.

All the same, small shifts in fertility or the retirement age can go a long way to alleviating the burdens of population decline. Raising the retirement age by a year or two can make the difference between the solvency and insolvency of pensions. On current rates, Italy will have a mere 1.4 workers to support each retired person by 2050. France and Britain will have a much more favourable age pyramid, with more than two workers per pensioner.

All this is a world away from the other rich country with demographic growth: America. Much American debate focuses on the role of marriage and the traditional family in fostering a healthy society. In Europe, by contrast, only countries with many births outside wedlock and with high female participation rates have reasonably high birth rates. Those that have sought to maintain traditional family ties have seen fertility collapse.

Europeans are only starting the process of recovery. Compared with America, even the growing parts of the continent have modest fertility rates and high dependency ratios. But if Europe has a demographic future it lies in Britain, France and Scandinavia, not across the Atlantic.