How many people can the Earth handle?


According to Alex Ezeh, professor of global health at Drexel University in Pennsylvania, the absolute number of people in a country is not the most important factor. Instead, it’s the rate of growth or decline of its population that is key to a country’s future prospects – it determines how quickly things change.

Take Africa, where Ezeh explains that there are dramatically different population growth rates right now, depending on where you look.

“In a number of countries, particularly in southern Africa [one of five regions defined by the United Nations]fertility rates have really dropped and contraceptive use is up – the population growth rate is slowing down, which in some ways is good news,” says Ezeh.

At the same time, some Central African countries still have high population growth rates, due to high fertility and longer lifespans. In some places it’s well over 2.5% per year, “which is huge,” says Ezeh. The population will double every 20+ years in a number of countries.”

Even within the same region, different countries can take startlingly different paths – Ezeh cites the example of East African neighbors Burundi and Rwanda. While the former is still experiencing high levels of growth – at 5.3 births per woman – the latter is experiencing a slowdown, with 3.9 births per woman in 2020 compared to 4.5 in 2010.

“I think the conversation about size and numbers is a misplaced conversation,” Ezeh says. “Think of a city that doubles every 10 years – and that’s a number of cities in Africa – whose government really has the resources to improve all the infrastructure that currently exists every 10 years, in order to maintain the right level coverage of these services.

Ezeh explains that in particular, it is difficult to sustain the development of human capital under conditions of extreme growth – which, according to research, plays an important role in the happiness of city dwellers, even more than the amount of money that they win. It is also believed to be an important predictor of economic growth, in addition to the number of people in a country.

“When economists think about it, a large population is ideal for many different outcomes, but do you reach that large population in 10 years, 100 years, or 1,000 years? The longer it takes to get there, the more you can put in put the right structures in the system that will support this population,” says Ezeh.

One factor with a well-documented role in slowing this rate of growth is the education of women, which has the side effect of increasing the average age at which they give birth. “Over time, women have access to education, they have positions outside the family, jobs, all those that compete with motherhood,” explains Ezeh.

However, Ezeh is keen to highlight the merits of education regardless of its impact on population size – it is one of the UN’s 17 Sustainable Development Goals. This goes to the heart of a modern view of demographic engineering – policies should be implemented for the benefit of society, and if they lead to beneficial demographic changes, that’s just a bonus.

“I think one of the things we don’t want to do is instrumentalize women’s education and make them go to school because we want women to have fewer children. .. there are a lot of positives that we can’t downplay thinking about it in terms of reduced fertility,” says Ezeh.

In fact, the cascading side effects of policies implemented for other reasons highlight a stark reality of population science – how inaccurate its predictions often are. Around the world, the decisions made by governments over the next few decades will have a huge influence on the number of people on the planet – with the power to move us from a future where there are 10 billion people, to a future where there are 15 billion, and vice versa.


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