In 1800, the world's population reached about 1 billion people. Since then, it has increased more than 7 times and amounted to more than 7.5 billion in 2017. The world's population is expected to exceed 10 billion by 2050. Will population growth continue? Will the current trend be sustainable over the long term? Should we try to reduce or stop this growth?
In a nutshell, the world's population is increasing as the number of births exceeds the number of deaths by a ratio of three to one. The surplus of births first occurred two centuries ago in Europe and North America, where mortality began to decline. This marked the beginning of what scientists call the demographic transition. The transition subsequently spread to the rest of the planet, as social and economic progress, coupled with improved hygiene and medicine, began to reduce mortality rates.
The annual population growth rate peaked half a century ago - over 2%. Since then, they have halved, to 1.1% in 2017. This trend is set to continue in the coming decades, as fertility declines globally from 5 children per woman in 1950 to 2.5 children per woman today. In 2017, areas where fertility remains high (more than 3 children per woman) include most of the countries of intertropical Africa and the region from Afghanistan to northern India and Pakistan. These areas of the planet will determine the growth of the world population.
population growth rates from 1700 to 2100 (forecast) as a percentage. & copy; Gilles Pison, based on United Nations data, CC BY
A key trend in the coming decades is population growth in Africa. The continent's population could quadruple over the next century, rising from 1 billion in 2010 to 2.5 billion in 2050 and over 4 billion in 2100, despite the negative impact of the AIDS epidemic and other factors. Now one person in six lives in Africa, and in a century the proportion is likely to be more than 1/3. Growth will be especially rapid in Black Africa, where the population could grow from 800 million in 2010 to 4 billion in 2100.
Fertility 2017 & copy; Gilles Pison, based on United Nations data., CC BY
Even if global fertility is only 1.6 children per woman, as in the case of Europe and China, the population will continue to grow for several more decades. The proportion of old and very old people is very small, so deaths are relatively few.
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Demographers were taken by surprise in the 1960s and 1970s when studies showed the onset of sharp declines in fertility in many countries in Asia and Latin America. Demographic predictions for these regions of the world have been revised downward.
Another surprise concerns intertropical Africa. The decline in fertility in the region was expected to start later than in Asia and Latin America due to slow social and economic development. But in intertropical Africa, the process is even slower. This explains the upward revision of population growth rates for the continent, which will host a third of the world's population by 2100.
Fertility by region. & copy; Gilles Pison, based on United Nations data., CC BY
Predicting the future for more than 50 years is a difficult task. If the small family becomes the dominant model in the long term, with an average fertility of less than two children per woman, the global population, peaking at 10 million, will begin to gradually decline to extinction. But another scenario is possible, in which fertility will recover in those countries where it is now very low, eventually reaching the rate of more than 2 children per woman worldwide. The result will be constant population growth and, again, the extinction of the human race, this time due to overpopulation.
Of course, people should be thinking today about the need for long-term balance. The planet's population will inevitably increase by 2-3 billion from now until 2050 due to demographic inertia that no one can prevent. However, we have the opportunity to change lifestyles and respect the environment more effectively and use natural resources more efficiently. In general, the long-term survival of humanity depends more on the pattern of life than on the size of the population.