The world is ill-prepared for the worldwide crash of the unborn children, which should have a “breathtaking” impact on societies, say the researchers.
Falling fertility rates mean that almost all countries could see their populations decline by the end of the century.
And 23 countries – including Spain and Japan – are expected to see their populations halved by 2100.
The counties will also age dramatically, with as many people turning 80 as there are births.
What’s going on?
The fertility rate – the average number of children a woman gives birth to – is declining.
If the number drops below about 2.1, then the population size begins to decrease.
In 1950, women had an average of 4.7 children during their lifetime.
Researchers at the University of Washington Institute of Metrology and Health Assessment have shown that the global fertility rate almost halved to 2.4 in 2017 – and their study, published in The Lancet, predicts that it will fall below 1.7 by 2100.
As a result, researchers expect the number of people on the planet to peak at 9.7 billion by 2064, before falling to 8.8 billion at the end of the century.
“It’s a fairly important thing; most of the world is in transition to a natural population decline, “said Professor Christopher Murray at the BBC.
“I think it’s incredibly difficult to think about it and recognize how important it is. It’s extraordinary, we will have to reorganize societies. “
Why are fertility rates falling?
It has nothing to do with sperm count or the usual things that come to mind when talking about fertility.
Instead, it is spurred by more women in education and work, as well as better access to contraception, which leads women to choose to have fewer children.
In many ways, the decline in fertility rates has been successful.
Which countries will be most affected?
The population of Japan is expected to drop from a peak of 128 million in 2017 to less than 53 million by the end of the century.
Italy is expected to see an equally dramatic demographic collapse from 61 million to 28 million over the same period.
Two of the 23 countries – including Spain, Portugal, Thailand and South Korea – are expected to see their populations fall by more than half.
“It’s breathtaking,” said Professor Christopher Murray.
China, currently the most populous nation in the world, is expected to peak at 1.4 billion in four years before declining by almost 732 million by 2100. India will take its place.
The UK is expected to peak at 75 million in 2063 and fall to 71 million in 2100.
However, this will be a truly global problem, with 183 of the 195 countries having a fertility rate below the replacement level.
Why is it a problem?
You might think it’s good for the environment. A smaller population would reduce carbon emissions as well as deforestation of agricultural land.
“This would be true except for the reverse age structure (more elderly than young people) and all of the uniformly negative consequences of an inverted age structure,” says Professor Murray.
- The number of children under five will increase from 681 million in 2017 to 401 million in 2100.
- The number of people over 80 will increase from 141 million in 2017 to 866 million in 2100.
Professor Murray adds, “It will create huge social changes. It worries me because I have an eight-year-old daughter and I wonder what the world will be like. ”
Who pays taxes in a massively aging world? Who pays for health care for the elderly? Who looks after the elderly? Will people still be able to retire?
“We need a soft landing,” said Professor Murray.
Are there any solutions?
Countries, including the United Kingdom, have used migration to increase their populations and to compensate for declining fertility rates.
However, that stops being the answer once the population of almost all countries decreases.
“We will pass from the period when it is a question of opening or not the borders to a frank competition for the migrants, because there will not be enough of them,” argues Professor Murray.
Some countries have tried policies such as improving maternity and paternity leave, free childcare, financial incentives and additional employment rights, but there is no clear answer.
Sweden has increased its fertility rate from 1.7 to 1.9, but other countries that have made considerable efforts to combat the “baby bust” have struggled. Singapore still has a fertility rate of around 1.3.
Professor Murray says, “I think people laugh at it; they can’t imagine it could be true, they think women will just decide to have more children.
“If you can’t [find a solution] then finally the species disappears, but it is in a few centuries. ”
- How are countries fighting against declining birth rates?
Researchers warn against reversing advances in women’s education and access to contraception.
Professor Stein Emil Vollset said: “Responding to declining populations is likely to become a primary political concern in many countries, but should not jeopardize efforts to improve women’s reproductive health or progress in the area of rights. women. “
What about Africa?
The population of sub-Saharan Africa is expected to triple to more than three billion people by 2100.
And the study indicates that Nigeria will become the second largest country in the world, with a population of 791 million.
Professor Murray says, “We will have many more people of African descent in many other countries as we go through this.
“Global recognition of the challenges of racism will be all the more critical if there are large numbers of people of African descent in many countries. “
Why 2.1 is the fertility threshold?
You might think the number should be 2.0 – two parents have two children, so the population remains the same size.
But even with the best health care, not all children survive to adulthood. In addition, babies are always slightly more likely to be men. This means that the replacement figure is 2.1 in developed countries.
Nations with higher infant mortality also need a higher fertility rate.
What do the experts say?
Professor Ibrahim Abubakar, University College London (UCL) said: “If these predictions are even half accurate, migration will become a necessity for all nations and not an option.
“To be successful, we need to fundamentally rethink global politics.
“The distribution of working age populations will be crucial in determining whether humanity thrives or dies. ”
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