Where have all the people gone?

Hot and crowded. That is the conventional wisdom on what Planet Earth will be like in the not-so-distant future. But the related question of how many of us there will be in 50 or 100 years matters too

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Are we facing a "hot and crowded" future, or is the world going to get smaller, much faster than people think? (James Cridland CC BY 2.0)

Hot and crowded. That is the conventional wisdom on what Planet Earth will be like in the not-so-distant future. Of these two predictions, it is temperature that receives far more attention.

But the related question of how many of us there will be in 50 or 100 years matters too. In Empty Planet, Canadian authors Darrell Bricker and John Ibbitson suggest — tentatively, yet persuasively — that mainstream opinion on the rate at which the population is growing could be wide of the mark. And by some distance.

The population of the earth today is estimated to be 7.7  billion. That number has been rising quickly for some time. In 1800, the global population was one billion; it reached three billion by 1959 and six billion around the turn of the millennium. The UN expects us to reach 10 billion by around the middle of this century and predicts that by 2100, a whopping 11.2 billion people will call Planet Earth home.

The UN acknowledges that prediction is an uncertain game. Eleven billion is what they see as the most likely outcome. In another scenario — the high variant one — the Earth will be swarming with 17 billion humans by 2100. But under the UN’s low variant forecast, women on average produce half a baby less than predicted. This difference in birth rates translates into a drastically different future: global population peaks at 8.5 billion around 2050 before going into decline.

Bricker and Ibbitson think this far less dramatic scenario is the most likely: “Across the planet, birth rates are plunging. That plunge is everything. That plunge is why the UN forecasts are wrong. That plunge is why the world is going to start getting smaller, much sooner than most people think.”

Central to the argument is an assumption embedded at the heart of the official demographers’ models, an assumption that they don’t think it is fair to make and argue is already being proved wrong. UN projections assume that “the fertility rate in a given country or region will match other countries or regions that have had similar experiences but that are further down the road”.

Birth rates fall as societies develop and urbanise. But do they do so in a predictable way? Will other factors — rights and education for women, for example — change in predictable ways around the world? Will an Asian country developing rapidly in the 21st century transform in the same way, and at the same rate, as a European country in the 19th century?

These are reasonable questions, which Bricker and Ibbitson are not alone in asking: “If you talk to some demographers off the record, you will hear them wonder whether the UN is keeping its population projections high, despite all the evidence to the contrary, to maximise a sense of crisis, thus justifying interventions to limit economic growth (there are few ardent laissez-faire capitalists at the UN) while ensuring the continued need for UN-based aid programs.”

In defusing the alarmism, the authors mix research, reportage, analysis and anecdote into a thought-provoking cocktail. The numbers are brought to life by conversations with prospective parents in Asia, Africa, Europe and South America about how many children they plan on having.

Who is right about global population in the coming decades will in large part be decided on the continent where the average age is just 19. Africa is large, populous and poor. How quickly it develops, and its birth rates fall, is the 11-billion-person question. The UN’s view is that Africa is going nowhere fast and that birth rates will stay higher for longer.

The authors travel to Kenya and find evidence to the contrary. The UN thinks Kenyan births will reach the replacement rate of 2.1 per mother in 2075. But if the country’s birthrate continues to fall at its current rate it will reach that milestone a quarter of a century sooner. If the latter is true in Kenya and across the continent, the demographic consequences will be huge.

Whether in Kenya or India, Brazil or Korea, Bricker and Ibbitson’s bearishness is convincing. But the real lesson from Empty Planet is just how unknowable the answer to the question both the UN and the authors endeavour to answer ultimately is.

The consequences of a shrinking global population receive less attention. However, their forecast is largely benign: the world will be “cleaner, safer, quieter”. Fewer people mean “weakening competition for scarce resources”.

It is here that Empty Planet is at its most disappointing. Much of the book is certainly a refreshing change from the Malthusianism that has dominated demographic debates ever since, well, Malthus. Bricker and Ibbitson point out just how wrong the doomsayers have been. Take Paul Ehrlich, whose 1968 bestseller The Population Bomb asserted that “the battle to feed humanity is over. In the 1970s and 1980s hundreds of millions of people will starve to death.” Rather than run out of food in the last 50 years, mankind has more or less eradicated famine. The human population doubled between 1950 and 2010 while food production tripled, despite only a 30 per cent increase in land under cultivation.

However, the authors themselves fall into this fatalistic way of thinking. The Malthusians have been wrong before not necessarily because they’ve overestimated the speed of population growth, as Bricker and Ibbitson think they are doing now, but because they’ve underestimated human ingenuity.

Resources might be scarce, but the bounds of what mankind can do with them is another matter altogether. Paul Romer, who received the Nobel Prize in Economics last year, has illustrated the virtually endless limits on what we can do with the planet’s resources using the periodic table:

To get some sense of how much scope there is for more such discoveries, we can calculate as follows. The periodic table contains about a hundred different types of atoms. If a recipe is simply an indication of whether an element is included or not, there will be 100 x 99 recipes like the one for bronze or steel that involve only two elements. For recipes that can have four elements, there are 100 x 99 x 98 x 97 recipes, which is more 94 million . . .

Once you get to 10 elements, there are more recipes than seconds since the big bang created the universe. As you keep going, it becomes obvious that there have been too few people on earth and too little time since we showed up, for us to have tried more than a minuscule fraction of the all the possibilities.

The more interesting question, then, is whether there might just be room for 11 billion, or even 17 billion, people on Planet Earth. Perhaps that is a matter for another book.

Ultimately, Empty Planet is a happy tale. Not because of the consequences of a possible fall in the earth’s population, but because of why it would have happened. In the past, global population has dropped because of plague, famine and war. A shrinking population of the sort envisaged here would be nothing more than the demographic consequence of prosperity and free will.