The 100 Million City: Is 21st Century Urbanization Out of Control?

Where countries are unable to control fertility rates and urbanization continues apace – within 35 years more than 100 cities will have populations larger than 5.5 million people. By 2100, say the authors, the world’s population centers will have shifted to Asia and Africa, with only 14 of the 101 largest cities in Europe or America.

What happens to those cities over the next 30 years will determine the global environment and the quality of life of the world’s projected 11 billion people. It’s impossible to know how exactly how cities will grow, of course. But the stark fact, according to the United Nations, is that much of humanity is young, fertile and increasingly urban. 

Bangalore, India

Population in 2015: 7 million
Projected in 2100: 21 million

Photograph: Manjunath Kiran

Temperature in the city has increased by 2-2.5C over the past three decades, while the water table has declined in places from 28 metres down to 300 metres deep; there has been an 88% loss of vegetation and a 79% loss in wetlands, and frequent flooding even during normal rainfall. There’s a fear that what has happened to Bangalore will happen to all Indian cities. “Air pollution is at dangerous levels, the water is polluted, there is nowhere for the waste to go, and the lakes have been killed,” says Ramachandra, head of the Energy and Wetlands Research Group at the Indian Institute of Science.

Kinshasa, DRC

Population in 2015: 12 million
Projected in 2100: 83 million

Photograph: John Wessels

Kinshasa had just 20,000 people in 1920. By 1940 it was home to about 450,000 people. Today it has possibly 12 million and is predicted to be Africa’s second largest city with 75 million people inside 50 years. By western standards it is a dysfunctional, sprawling megalopolis, ringed by vast shantytowns of informal settlements, their infrastructure nonexistent or collapsing.

By 2100, about 40% of all humans and nearly half of all children in the world will be African – one of the fastest and most radical demographic changes in history.

Mexico City

Population in 2015: 20 million
Projected in 2050: 25 million

Photograph: Brett Gundlock

“No one expected Mexico City to grow so much,” says Connolly, a professor of urban sociology at the Universidad Autónoma Metropolitana. “Now the city has stopped growing and medium-sized cities are growing fastest.”

The city is still vastly overcrowded, massively polluted and predominantly poor, with little space to build the 50,000 new houses a year that it needs. But it shows that rapid change can be controlled, and that urbanisation has its benefits. Most people can read and are housed. They don’t expect to die at five. All in all it’s been a successful transition, though fraught with future environmental risk.


Fast-growing cities in Africa and Asia could learn from Mexico City’s mistakes, Connolly says. “Planning and thinking was geared to the idea that cars could circulate. Only 30% of Mexico City has a car, but the city was designed for the car. The 19th-century sanitary revolution has to be rethought. The environmental impacts of urbanization are much worse outside cities.”

The shantytowns and informal settlements that ringed Mexico City in the 1970s are now being upgraded. However, environmental issues are still not high on the agenda, and the city has a semi-permanent water crisis.


Population in 2015: 1.3 million
Projected in 2050: 1.3 million

Photograph: Kateryna Negoda

European cities are some of the world’s richest, and most are expected to barely grow or even shrink over the next 50 years. Declining birth rates, ageing populations and good infrastructure allow many to now focus on the environment.

But even if they aren’t growing at nearly the rate of other cities, they are some of the world’s biggest consumers of energy and resources and emissions.

The city has set the ambitious goal of becoming the world’s first carbon neutral capital by 2025. As well as tackling energy production and consumption.

Many cities are already investing in clean transport and water, sewage, renewable energy, planning, wellbeing and good housing for all. Others face what seem like insurmountable problems.

Learn more about these and other cities

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