Projections suggest cities will swell at an astonishing pace – but whether that means our salvation or an eco-disaster is by no means certain
No one foresaw what happened next. In just two generations Lagos grew 100-fold, from under 200,000 people to nearly 20 million. Today one of the world’s 10 largest cities, it sprawls across nearly 1,000 sq km. Vastly wealthy in parts, it is largely chaotic and impoverished. Most residents live in informal settlements, or slums. The great majority are not connected to piped water or a sanitation system. The city’s streets are choked with traffic, its air is full of fumes, and its main dump covers 40 hectares and receives 10,000 metric tons of waste a day.
But new research suggests that the changes Lagos has seen in the last 60 years may be nothing to what might take place in the next 60. If Nigeria’s population continues to grow and people move to cities at the same rate as now, Lagos could become the world’s largest metropolis, home to 85 or 100 million people. By 2100, it is projected to be home to more people than California or Britain today, and to stretch hundreds of miles – with enormous environmental effects.
Hundreds of far smaller cities across Asia and Africa could also grow exponentially, say the Canadian demographers Daniel Hoornweg and Kevin Pope at the University of Ontario Institute of Technology. They suggest that Niamey, the barely known capital of Niger – a west African country with the highest birth rate in the world – could explode from a city of fewer than one million people today to be the world’s eighth-largest city, with 46 million people, in 2100. Sleepy Blantyre in southern Malawi could mushroom to the size of New York City today.
Under the researchers’ extreme scenario – where countries are unable to control fertility rates and urbanisation 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 the Americas.
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. The median age of Nigeria is just 18, and under 20 across all Africa’s 54 countries; the fertility rate of the continent’s 500 million women is 4.4 births. Elsewhere, half of India’s population is under age 25, and Latin America’s average age is as high as 29.
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Population predictions for the world’s largest cities in the 21st century - Daniel Hoornweg, Kevin Pope, 2017
Daniel Hoornweg, Kevin Pope
We project populations to 2100 for the world’s larger cities. Three socioeconomic scenarios with various levels of sustainability and global cooperation are evaluated, and individual “best fit” projections made for each city using global urbanization forecasts. In 2010, 757 million people resided in the 101 largest cities – 11 per cent of the world’s population. By the end of the century, world population is projected to range from 6.9 billion to 13.1 billion, with 15 per cent to 23 per cent of people residing in the 101 largest cities (1.6 billion to 2.3 billion). The disparate effects of socioeconomic pathways on regional distribution of the world’s 101 largest cities in the 21st century are examined by changes in population rank for 2010, 2025, 2050, 2075 and 2100. Socioeconomic pathways are assessed based on their influence on the world’s largest cities. Two aspects of the projections raise concerns about reliability: the unlikely degree of growth of cities suggested for Africa and the growth of cities in coastal settings (and likely global immigration). Trends and the effect of sustainable development on regional distribution of large cities throughout the 21st century are discussed.