The United Nations recently surveyed 50 Nobel laureates asking them what they believed was the biggest underlying threat to mankind. 30% cited population growth and the resulting environmental degradation. 23% cited nuclear war. Nothing else came close. Population growth above nuclear war.

The link between population growth and climate change is not a simple 'cause and effect'. However, the more of us there are, the greater the demand for energy and right now, only 30% of our electricity comes from renewable energy sources. The race to prevent catastrophic climate change must involve slowing population increase.

Take a look at the website www.worldometers.info/world-population and marvel at the rate at which the human population is increasing.

Every 10 seconds, 22 extra humans are added to the planet. That’s 190,000 each day. A jaw-dropping 71 million in 2024.

The good news – and we desperately need some of that – is that the rate of increase is slowing although it’s not an F1 racing car – 200mph to a stop in 4 seconds. Instead, population growth is an oil tanker – engines in full reverse, then hope you’ve got 10 miles of clear water. The population engines are in reverse in parts of the world and over the next 10 years we’ll begin to see the population rising less quickly. It might even stop rising before the end of the century.

Predicted world population

By United Nations, DESA, Population Division

Figure 1

Predicting future population growth is not straightforward. There are so many variables at work which can increase or decrease birth and death rates. The solid red line above is the UN's best estimate based on the available data. Of course, what cannot be accounted for is the impact of climate change on human population. If global temperature increases by 3°C or more before 2100, then the population is unlikely to reach 10 billion.

When I was a 9-year-old kid in 1965, 3.3 billion humans walked this planet. No one was talking about climate change even though, in 1896, a Swedish scientist Svante Arrhenius had figured out that burning fossil fuels would warm the planet. In 1965, the population was growing faster than at any time in human history – over 2% per year. 2% of 3.3 billion is over 60 million, the equivalent of Italy’s current population added to the world in just one year. 60 million more carbon footprints, each one sending ever more greenhouse gases (GHGs) into the atmosphere. The link between population growth and climate change seems a no-brainer. Doesn’t it?

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1965: Planet Earth (3.3 billion) + Italy (60 million)

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2023: Planet Earth (8 billion) + UK (69 million)

The average number of children that women were having throughout their reproductive years (birth rate) in 1965 was 5. But look how that number falls until by 2023, it’s down to 2.25.

Lower birth rates are surely good news for population growth. But as birth rates were falling across the world, so were mortality rates, especially for children under the age of 5. In 1990, global infant mortality was 144 per thousand, while in 2015 this had fallen to 38. Falling birth rate, falling death rate – so what’s happening to population growth rate? In 2023, this had fallen below 1% to just 0.88%, a lot lower than the dreaded 2% in 1965. Sound promising? We should bear in mind that 0.88% of 8 billion is still more than 2% of 3.3 billion. 60 million extra people in 1965, but over 70 million in 2023. That’s more than the size of the UK’s current population. An extra UK in just one year!

The good news is that most population authorities believe that figure will drop every year from henceforth until eventually reaching zero at which point the number of Homo sapiens will begin to fall. In the UN’s predictive graph below, that will occur around 2085.

Population growth rate

2024 United Nations, DESA, Population Division. CC BY 3.0 IGO.

Figure 2

Population growth rates vary enormously across the world. In the map below showing each country’s growth rate (2024), most have positive growth but there are a significant minority whose populations are shrinking, coloured orange in Fig. 3.

Figure 3

Projected population growth for 2024

Continental Population growth rates

Table 2

One continent stands out in Table 2 – Africa. Whilst growth rates are falling rapidly in most areas of the world, in Africa they are not.

Click here to discover more about the current population trends in sub-Saharan Africa and the worrying predictions for countries in that region.

Photo: Lagos, Nigeria.

Population: 1990 - 4 million; 2015 - 12 million; 2024 - 16.5 million.