Be fruitful and multiply — but not that fast 

“Earth before everyone’s eyes is becoming more and more cared for and populated than ever before as days go by. Everything is already accessible, everything is known, fruits of human labour can be seen everywhere […] The best evidence of the human numerousness: we are a burden for the world […] The nature can no longer sustain us.”

These words were written far from the 19th or even the 20th century. They were musings of Tertullian, early Christian author and philosopher from Carthage in the beginning of the 3rd century AD. Back then there were only 240 million people on the planet or 3% of the current world population.

There were relatively few people on our planet almost throughout the entire history of the human civilisation, and their number was growing very slowly. If we take roughly 10,000 years BC, over this period, the total number of people on our planet barely reached 5 million. However, the shift from hunting and gathering to agriculture acted as a powerful stimulus to form communities, and the numbers started to go up. When the Common Era dawned upon the humanity, there were possibly 200 million people in the world, while this number stood at around 750 million at the beginning of the Industrial Revolution. The global population reached the crucial milestone of 1 billion people between the 18th and the 19th centuries. It began multiplying at an unprecedented rate from that point on.

In 1925, the 2 billion mark was achieved. In 30 years’ time, it was already 3 billion. The 1960-1970s are defined by a demographic boom: scientific, medical, and technological breakthroughs made it possible to cut down death rates, while the spread of the carbon industry and energy along with the green revolution supplied an ever-increasing number of people with food and other resources. In the mid-1960s, the population increase reached record-high levels and another billion people were added to the count already in 1974 (this time it only took 14 years). Each next billion took less and less time. And here we are, there are now 8 billion people in the world.

The global population continues to grow, albeit more slowly

Despite the fact that the number of people on the planet is still going up, the speed at which it’s happening is slowing down globally. In the mid-1960s, the increase equaled 2.1% per year, a record-high number. Meanwhile, it dropped below 1% a year in 2021. In the 1950s and 1960s, the total fertility rate was 5 births per woman, and today it’s more than halved (2.4).

Nowadays, more and more countries report longer lifespans and improved standards of living, which exacts a natural birth rate decrease. This means that we will see an even slower population growth and reductions globally in the future.

But the demographic situation in the world is not homogenous. Rich Western states experience lower birth rates, mostly due to women obtaining better access to education, work, and contraception. Meanwhile, populations are still growing in poorer countries where women are still struggling with it. On top of that, the child death rate is very different in the world: in tropical Africa, it is 14 times higher than in Europe or North America.

In Africa, South and Central Asia, more than 220 million women give births more often than they would like to, while the UN Population Fund counted that almost half of all pregnancies in 2022 were unplanned. It all provokes a thought that the birth limit policy should not by default enforce repressions against populations, as it happened with China’s one-child policy or India’s forced sterilisations in the 1970s. It is essential for all women around the world to have access to education, both traditional and sexual, contraceptives, and opportunities to plan family size.

Humankind will reach its peak population by the end of the 21st century

Scientists have no doubt that the demographic increase is subsiding, but the world population will continue to go up in the next few decades. However, there’s still no clear understanding when it will actually start shrinking.

The most recent UN forecasts show that the global population will be expanding throughout the whole of the 21st century and will hit 9.7 billion by 2050. Later, this number is expected to peak at around 10.5 billion in the 2080s and will remain at this level until the end of the century. At the same time, the UN believes that the highest population number that the planet can get by 2100 is 12.4 billion. Africa’s sub-Saharan states will contribute the most to this increase: the region will become the most populous in the world by the 2060s.

Despite the fact that the UN forecasts envision that the global population will start shrinking after 2100, some researchers consider it to be alarmist. Particularly because it does not factor in lower birth rates due to the ongoing urbanisation. Moreover, the UN model includes the possibility that birth rates in some countries would start going up again due to the improved financial situation.

There’s another forecast made by the Institute for Health Metrics and Evaluation at the University of Washington in 2020. It says that the world population will continue to grow until 2064 and will reach 9.7 billion. It will then start shrinking and will have gone down to 8.8 billion by 2100. The authors of the research believe that the main factor behind this trend will be universal access to female education and to contraceptives, especially in Africa.

At the same time, both forecasts profess that the 21st century will be the last one when the population of our planet will grow. Nevertheless, overpopulation is still very much an issue in 2022.

What the global overpopulation leads to

Discussions about the fact that overpopulation puts a greater strain on nature first drew public attention during the demographic boom in the 1960s. Well, the discussion was not in the form of scientific publications, it was a tendentious book by American biologists Paul and Anne Ehrlich. Having travelled to India and being shocked by swarms of people in the streets, they wrote a best-selling book titled The Population Bomb in 1968.

The Club of Rome was established the same year. It was an association of European intellectuals who sought to draw attention to global issues of the humanity. The first club report, the Limits to Growth, came out in 1974: it was focused on overpopulation and reaffirmed that a humanitarian catastrophe was unavoidable. The report was highly publicised: the UN declared the year it was published World Population Year and called the first global convention on this issue.

At the beginning of the 21st century, the UN ordered an overall assessment of the human impact on nature and learnt that we had affected ecosystems more quickly and strongly in the past 50 years than ever before. The humanity’s growing demand for food, water, wood, fibres, and fuel as well as water, air, and soil pollution have led to such widespread (and often irreversible) losses in our biodiversity that the ability of our planet to sustain future generations is in serious doubt. In 2019, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) published a detailed report that confirmed that the population growth was one of the reasons behind the global biodiversity loss.

In 2021, the platform joined forces with the Intergovernmental Panel on Climate Change (IPCC) to issue a report which shows that in the past 150 years the excessive consumption of coal, gas, and oil as well as the growth of industries and power industry, interference in land and water landscapes caused climate change. For instance, the increase in greenhouse emissions is directly linked to the population growth: on average a 1% increase in population is associated with a 1.5% increase in global carbon emissions.

The more there are of us, the bigger is the demand to burn fossil fuel and produce, for example, cement, the more cars and exhaust fumes there are, and the weaker our ecosystems are that naturally absorb carbon gases.

At the same time, not all countries in the world are equally responsible for the impact on ecosystems and climate. Between 1990 and 2015, 3 billion of the least developed regions globally were exacting just 7% of the global greenhouse emissions, while the 1% of the richest people on the planet were bringing in twice as much (15%). Meanwhile, climate change consequences will affect everyone, including Russia, whose population is dropping.

In 2017, more than 15,000 scientists from 184 countries signed a Warning to Humanity. The document claims that the quick population growth is behind many modern ecological and public threats. In two years’ time, 11,000 scientists from 153 states again drew attention to it, calling to stabilise and preferably reduce the global population. Recent research, whose authors were comparing ways to reduce personal carbon footprints, identified that it is most effective to have fewer children.