Today is World Population Day, when the urgency of our growing population is brought into focus. And for good reason: the UN has projected that the world population will reach 11.2 billion by the end of the century. That is another four billion people than we have today. So what will life in 2100 be like?

The world population is growing at a gradually slower pace than in the last few decades, but it’s still increasing substantially. Roughly 83 million people are being added to the world’s population every year and this upward trend in population size is expected to continue.

The UN has a good track record for its population predictions. In 1948 the UN projected world population would be around six billion in 2000, only less than 5% off the realised number.

So with World Population Day upon us, what will the potential impact of this population expansion be, and how will it shape life in 2100?

Africa will contribute nearly half of the global population by 2100

Most of the projected population growth is expected to come from Africa. The continent is expected to more than double its population by 2100 to have 49% of the global population compared to 16.6% now, as predicted by the UN.

Africa has the highest rate of population growth currently, at 2.55% annually in 2010-2015. Rapid population growth is expected to continue, even if there is a substantial reduction of fertility levels in the near future, because of the large number of young people currently on the continent.

This in contrast to Europe, whose population is expected to shrink as fertility is below levels needed for full replacement of the population.

Life in 2100 will be characterised by urbanisation and mega-cities

By 2100, it is predicted 80% of the world’s population will live in cities.

Increased urbanisation is likely in a bid to support the sheer quantity of people. This will result in the emergence of new cities and mega-cities with populations of over 20 million.

According to the University of Ontario’s projections, Lagos, Nigeria will be the largest city in 2100, with approximately 88 million people.

An ageing population

Globally, the number of people aged 80 or over is projected to triple by 2050, from 137 million in 2017 to 425 million in 2050, according to UN report. By 2100, it is expected to increase to 909 million, nearly seven times its value in 2017.

This will have a profound effect on societies, with specific implications for healthcare, pensions and social protection systems. The burden on younger generations to support this will be substantial.

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Global life expectancy is also projected to increase from 71.9 years in 2015 to 82.6 years in 2100.

The number of languages spoken will decrease

Right now, there are over 7,000 languages spoken around the world. In the future, it is possible that less common languages will stop being used as people become increasingly integrated. As a result, the world could only have a few hundred languages left.

English will most likely become the most used language around the world, knocking Mandarin Chinese off the top spot.

Alternative energy sources

Finite sources of energy such as oil, natural gas and coal that supply most of the global energy today will become increasingly scarce. This will mean seeking alternative renewable energy sources to maintain supply to the world’s population as demand increases.

By 2100, renewable energy sources, especially hydropower, will likely provide nearly all energy to the world.