Megacities set to grow in importance

Population movement tends to happen slowly, driven by factors such as births, deaths, age structures and migration. However, the recent UN World Urbanization Prospects report shows how demographic change can also happen comparatively quickly through the prism of the growth of megacities, which are defined as urban areas with more than 10 million inhabitants.

The UN report shows that Cairo is the only megacity outside of Asia to make the top 10 of the world’s largest urban areas, with its population of about 23 million. Meanwhile, Lagos (about 18 million), is the largest city in sub-Saharan Africa. Other cities in the region that are on track to become megacities by mid-century include Addis Ababa, whose current population is just over 6 million.

Yet, as important as the Middle East and Africa — long seen as the cradles of civilization — are in this global story, there is an even larger narrative in play about how the world’s center of population growth is shifting east. Not only does Asia now boast nine of the world’s top 10 most populous cities, but it also hosts an astonishing 19 of the world’s 33 megacities.

There is an even larger narrative in play about how the world’s center of population growth is shifting east

Andrew Hammond

According to the UN, Jakarta (42 million) has now overtaken Tokyo (33 million) as the world’s largest city. The other cities in the top 10 are Dhaka (at least 36 million), Shanghai (29 million), New Delhi (28 million), Guangzhou (27 million), Manila (24 million), Kolkata (22 million) and Seoul (22 million).

The total of 33 megacities is more than four times larger than the eight that existed in 1975. This comes in a context where the proportion of the global population living in cities is expected to increase to about 70 percent by 2050. This, combined with the overall growth of the world’s population, could add another 2.5 billion people to major urban areas by mid-century. Already in some cities, there are more than 10,000 people living in an area of just 1 sq. km.

Looking to 2050, Dhaka is expected to become the world’s most populous city, overtaking Jakarta. The UN report also forecasts that several other urban areas will join the megacity category, including Addis Ababa, Kuala Lumpur and Hajipur.

However, a small number of these megacities, like Tokyo and Seoul, will experience a declining population due to aging and falling birth rates. This highlights how demographic decline in some developed nations will be the counterpart to high population growth in many emerging markets.

So, there is no question that the center of population gravity, as well as economic, is shifting eastward, even if there are some disputes around the exact populations of many of these cities. Part of the reason for the significant changes in the latest figures from the UN is an alteration to its methodology for calculating the size of major urban areas.

Given the rapid growth of cities like Jakarta, governments are being forced to address key sustainability questions

Andrew Hammond

As a result, Jakarta moved from 30th position in 2018 to seize top spot from Tokyo, which was the world’s largest city from 2000 to 2025. The UN has shifted from an administrative boundary-based tally to a methodology based on continuous urban areas, in which economic and living spheres are seen as connected. So, whereas the Indonesian government’s estimation of Jakarta’s population is 11 million people in an urban core, the UN calculates the entire greater capital region by grouping together suburbs including Bogor, Depok, Tangerang and Bekasi.

Given the rapid growth of cities like Jakarta, governments are being forced to address key sustainability questions. These include whether it will be possible to continually meet the everyday needs of food, water and health, while dealing with environmental stresses exacerbated by the effects of climate change.

Jakarta is situated in a low-lying coastal area of Java and it is already facing major challenges from traffic congestion, air pollution and subsidence. Some areas of the megacity are sinking by as much as 25 centimeters a year thanks to increasing groundwater extraction and nearly 40 percent of the city now lies below sea level. Up to a quarter of the city could be underwater by 2050.

The challenges are so big that Indonesia is building a new capital city in Nusantara in Borneo’s East Kalimantan province. However, the UN estimates that some 10 million more people will still be living in Jakarta by 2050.

The growing resource challenges facing megacities highlight the key issue of preparedness. As many of these cities continue to grow, demand will increase as supplies of food, water and resources for industries and infrastructure require energy for transport, with the associated carbon emissions contributing to global warming.

The main risk for riverine megacities is their increasing vulnerability to rising sea levels and flooding. The key preparations required include state-of-the-art early-warning and monitoring systems to protect coastal communities.

The larger the urban area, the greater the damage that natural hazards can inflict. And it may become increasingly hard to protect lives, even if there are good warning systems. As major hurricanes in some cities have shown, there is now sometimes insufficient time to evacuate safely.

So, there is a growing need for cities to also develop emergency refuge areas. Governments must consider how to best identify and design such emergency centers and how they should be connected to the wider urban system, including transport.

Taken together, despite the economic success of many megacities, now is the time to prepare for the growing risks that these massive urban centers face, including environmental stress. Many nations are now seeking to redefine what sustainability means due to their population growth.

• Andrew Hammond is an associate at LSE IDEAS at the London School of Economics.