Discover the top ten largest megacities across the globe and why some of their populations are decreasing
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Megacities – defined as a city with more than 10 million inhabitants – are found globally, with 44 megacities in five continents. By 2050, it is projected that there will be 67 megacities, and the population of the top 1000 largest global cities will increase by more than half a billion.
Megacities in emerging Asia Pacific, as well as Africa, are set to be the fastest growing. However, while some may experience an uptick in their populations, others – particularly in China, Europe, and advanced Asia Pacific – are predicted to plateau or even decline. Here are the current Top 10 in reverse order:
10) Osaka, Japan – 19 million
Located on the island of Honshu, Osaka is Japan’s second-largest city and the capital of Osaka Prefecture. Recently, the population of the megacity has begun to decline – with the period between 2010-2015 marking the city’s first reduction in its population in almost 70 years.
Factors for the declining population include low fertility rates and deaths which have outnumbered the birth rate – which fell below 1 million in Japan for the first time back in 2016, and has plummeted to 800,000 births per year in 2022.
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9) Mumbai, India – 21.3 million
Known as India’s financial and commercial hub, Mumbai is the capital of Maharashtra state, located in southwestern India. Despite having the main port in the country, the megacity boasts high biodiversity in its Sanjay Gandhi National Park – which protects 104 sq km within the megacity – with 280 bird species, 150 butterfly species and 40 species of mammals.
The population of Mumbai has grown by 1.6 per cent since 2022, attributed to a higher fertility rate and migration from rural to urban areas – but this has also led to an increase in the number of residents living in slums, including the largest in Mumbai, Dharavi.
8) Beijing, China – 21.8 million
Beijing, the capital of China, had its population limited between 1980 and 2016, when the one-child policy was enforced across the country to curb its rapid growth – with 400 million births estimated to have been prevented across China.
After the policy was scrapped, Beijing announced plans in 2017 to limit the number of residents in the megacity to 23 million by 2035, amid concerns over pollution, limited resources as the population grew and unmonitored economic development.
Between 2021 and 2022, Beijing’s population dropped for the first time in 19 years by 84,000 people, with factors including changing attitudes to marriage and family; gender inequality and the rising costs of raising a family.
7) Cairo, Egypt – 22.2 million
The Egyptian capital has grown by over 430,000 people in the last year, a 2 per cent increase compared to 2022. If growth were to continue at this rate, the population of Cairo could double by 2058 – and it has already increased rapidly from just 2 million people back in 1950.
Cairo’s climbing population can be attributed to two main factors: high fertility rates across Egypt, and population momentum – when a large proportion of the population are in their childbearing years, which causes an increased number of births. The sooner the fertility rate drops, the fewer the number of people will be added to the population due to population momentum.
With 27 per cent of Egypt’s population living in poverty – and Cairo is estimated to contribute to 18 per cent of this – the megacity is suffering from its rapidly growing population and insufficient resources to support it. Poor quality canal water, often used due to the limited supply of piped water, can cause diarrheal disease, estimated to lead to the deaths of 17,000 children each year in the megacity.
6) Mexico City, Mexico – 22.3 million
Mexico City – the capital of Mexico and the largest Spanish-speaking city in the world – is located in the highlands of the country, making it an optimal crossroads for trade between the north, the coasts of the Gulf of Mexico and the Pacific Ocean, and southern Mexico.
The population of Mexico City has grown by 0.89 per cent in the last year, according to the UN World Urbanization Prospects – and is projected to grow by 3.2 million people in the next five years.
Its population makes up 20 per cent of the country’s total – but there is a clear economic divide between those with wealth and individuals living in shantytowns and lower-class neighbourhoods, such as Neza-Chalco-Itza, a shantytown with a population of 4 million people. The megacity also faces poor air quality, due to its location between two mountain ranges which act to trap pollution.
Previously, urban migration was the leading factor for population increase in the megacity, but now it is slowed – meaning that the population is rising due to natural growth.
5) São Paulo, Brazil – 22.6 million
Regarded as Brazil’s financial hub, São Paulo is the largest Portuguese-speaking city in the world, around 350km (220 miles) southwest of Rio de Janeiro. By 2030, the UN estimates that São Paulo will reach a population of over 23 million people.
Since São Paulo’s industrialisation after World War II, the megacity’s industrial sector attracted millions, rocketing its population from just 32,000 people in 1880 as coffee production increased with modernisation.
With a population growth of 0.89 per cent since 2022 – around 189,000 people – São Paulo has a large number of immigrants, mainly of Italian, Portuguese and African descent. However, despite the fast population increase, major planning to accommodate residents has not developed as quickly. Public transport is ineffective – with rising fares and poor service – resulting in traffic on major roads in the megacity; and around 5 per cent of the population – or 830,000 people – live in slums.
4) Dhaka, Bangladesh – 23.2 million
Situated near the Buriganga River, Dhaka – the capital city of Bangladesh – is a highly-industrialised region, with industries including embroidery, silk and jewellery, as well as a profitable, export-orientated garment industry. Initially, migration from rural areas to the megacity contributed to its rapid population growth of over 60 per cent during the 1960s and 1970s.
But with a growth of over 730,000 people in the last year – representing a 3.25 per cent increase – the megacity has faced strain as Bangladesh suffers from high rates of poverty – rising from 21.6 per cent in 2018, to 42 per cent in 2020 following the COVID-19 pandemic.
3) Shanghai, China – 29.2 million
Shanghai is China’s largest city and a major financial hub, and its population continues to rise – growing by over 690,000 people in the last year alone. Between 1949 and 2010, rapid industrialisation and urbanisation increased the number of people who lived there.
The population of this megacity is expected to almost double by 2050 to over 50 million – but plans have been made to stop it from rising this quickly.
In 2017, the Shanghai municipal government announced it would cap the megacity’s population at 25 million by 2035, in order to combat ‘big city disease’ – a term used to refer to the multitude of factors that can impact a megacity as it grows, including environmental pollution, traffic congestion and overstretched public services.
2) Delhi, India – 32.9 million
Growing by over 875,000 people last year, Delhi is the world’s second-largest megacity, but suffers from pressures to improve its infrastructure as a result of its rapidly-growing population. Migration is a significant factor in Delhi’s rising population, with 283,000 people migrating to the megacity in 2021 alone.
By 2025, Delhi’s population is expected to hit 36 million – and by 2030, it is projected to become the largest megacity in the world. By 2050, forecasts suggest the megacity’s population will rise to almost 47 million.
With large quantities of air pollution – worsened by the number of vehicles in Delhi doubling from 1990 to 2012 – the government has begun to use several methods to combat worsening air quality, including a project to map sources of air pollution in real-time.
1) Tokyo, Japan – 37.1 million
Tokyo is the world’s largest city – with a population size four times larger than London – but its population dropped by over 79,000 people in the last year.
With a low immigration rate, low fertility, and the world’s most ageing population – it is expected that Japan’s population, and consequently Tokyo’s, will continue to plummet in the coming years. In the next 90 years, the megacity’s population is expected to halve – and there are concerns over the ageing of the working population and the consequences it will have upon Tokyo’s position as an international city.
