We hear a lot about how the world’s population is soaring. Human numbers are well past seven billion, more than four times the figure it was a hundred years ago. Pessimists say that overpopulation is driving global warming, and will one day make the planet uninhabitable.
But there is a more optimistic take on demographic trends. For we are solving what a generation ago seemed about the most difficult problem for the future of humanity. The population bomb is being defused.
Globally, up until the mid 60s, women were having five or six children, and thanks to better public health and medicine, most of those children were growing up and having their own children. Our numbers were doubling every generation.
Doubling food production seemed impossible. In 1968, the American biologist Paul Ehrlich wrote the million-selling The Population Bomb, in which he said: “The battle to feed humanity is over… Sometime between 1970 and 1985, the world will undergo vast famines. Hundreds of millions of people are going to starve to death.”
What happened? Well, the world’s population has more than doubled since Ehrlich wrote his book. And we’ve had some famines, but nothing on anything like the scale Ehrlich predicted. Because, amazingly, food production doubled thanks to the “green revolution” of high-yield crop varieties.
That bought us time. Time we have been using well. Today, women have only half as many children as their grandmothers did back in Ehrlich’s day. The global average fertility rate is now just under 2.4. It is a reproductive revolution going on round the world that we hear remarkably little about. That rate of 2.4 is pretty close to the level needed to keep up numbers which, allowing for girls who don’t make it to adulthood, is globally around 2.3 children per woman.
Half the world now has fewer than the “replacement level” of children. As the Swedish statistician Hans Rosling has pointed out, we have now reached “peak child”. Without an influx of migrants, populations are set to decline in Europe, North America and the Caribbean, most of the Far East, and much of the Middle East.
This revolution has been spectacular. Take Iran. In the past 25 years, behind the veil, the number of children born to the average Iranian women has crashed from eight to 1.8. Women in Teheran today have fewer children than their sisters in London or New York.
Outside China, this has rarely been driven by coercive state policies. Mostly small families are free choices. The trend is almost universal.
India is now below 2.5, less than half the figure in 1980. In Bangladesh – one of the world’s poorest nations, where girls are among the least educated in the world, and most marry in their mid-teens – you might expect big families. Yet they have on average of only 2.2 children today. In Brazil, where the priests vehemently oppose contraception, the average is now down to 1.8.
This baby crash is resulting in ageing, and sometimes outright demographic decline. Bulgaria has lost a fifth of its population since the 1990s. If Italy gets stuck with its present 1.4, and stops migrants coming in, then its population will halve by the end of the century.
Reversing the trend is hard. Singapore has been bribing couples to have more babies for a couple of decades now. Yet the country’s fertility rate remains, at 0.8, the world’s lowest.
What is going on? The reproductive revolution is the result of a health revolution. In the 20thcentury, the world largely eradicated the diseases that meant most children did not reach adulthood. For a while, mothers continued to have the five or six children traditionally necessary to ensure the next generation. Populations boomed. But now, societies are adjusting to the new demographic reality.
There are holdouts, of course. In much of poor rural Africa, women still have five or more children. The kids come in handy, minding the animals and working in the fields.
Cities are different, however. More than half the world now lives in cities. And in cities children are an economic burden. People in urban areas have fewer children, especially in Africa. We are used to thinking of megacities as symbols of over-population. But they are also part of the solution.
None of this means women don’t still need help to safely achieve their ambitions of small families. President Trump’s ban on giving US aid to organisations that provide family planning services is a blow. Nor do these trends mean that world population growth has ceased. Our current 7.4 billion may rise to 10 billion or more, because we are living for longer and because the huge numbers of young women born during the boom years of the 20thcentury remain fertile. But assuming Africa follows a demographic path similar to that seen in the rest of the world, then we can expect peak population well before century’s end.
What does this mean for the future habitability of our planet? The promise of peak population rather than endless growth is good news, of course. But don’t put out the flags. While Ehrlich turned out to be wrong about the population bomb, he was right in his analysis that humanity’s impact on the planet depends on a combination of three things: human numbers, what those individuals consume, and how we make what they consume.
As the rate of population growth subsides, our rising impacts on the planet – whether climate change or deforestation or biodiversity loss – are driven less by a population bomb and more by a consumption bomb. Economists predict the world’s economy will grow by 400% by 2050. If so, only a tenth of that growth will be due to rising human numbers.
We in the rich world have no right to pull up the drawbridge on the poor, so consumption will continue to rise. The real existential challenge for humanity this century must, therefore, lie in activating the third element in Ehrlich’s calculation: how we produce what we consume.
That means recycling materials; generating our energy in ways that don’t fill the atmosphere with climate-changing gases; and curbing our wasteful use of water and land, especially for agriculture. Eco-efficiency is the new mantra for achieving these goals, and we are making progress particularly following the soaring investment in wind and solar power.
Through such means, some resource analysts say that the rich world has reached “peak stuff”, and hope that better technology will allow the rest of the world to follow soon. It is no longer unreasonable to think that a properly run planet has the resources to give good lives to 10, 12 or even 15 billion people.
Nothing is certain. But perhaps our successors will be able to look back on the 21stcentury as the moment when world population stabilised and technology finally adapted to meet the needs of a more crowded world.