Where are largest cities in the world? 2015 edition

The world's biggest cities from above. Image: Getty.

The number of people who live in a city, as we may have mentioned before, is surprisingly hard to work out. That's partly because populations shift and change, unnoticed by demographers.


Mostly, though, it's because you quickly run into the fact that different authorities define their cities in entirely incompatible ways, rendering any attempt to compare them a bit like comparing apples with trucks. What you really need is a single source that follows a single set of rules: the results may not be perfect, but at least they'll be consistent.

That’s where Demographia comes in. The St. Louis-based consultancy was founded by the urban planner Wendell Cox (who, unusually for someone in that line of work, likes to write articles for conservative publications about the benefits of private car ownership). It also has a website that is, with the best will in the world, not massively easy on the eye.

But every year Demographia publishes something rather good: the World Urban Areas Report, a sort of bumper book of city population stats. You can check out the 11th edition here.

Here’s how it defines a city:

An urban area ("built-up urban area," urbanized area or urban agglomeration) is a continuously built up land mass of urban development that is within a labor market (metropolitan area or metropolitan region). An urban area contains no rural land... [It] is best thought of as the “urban footprint” – the lighted area that can be observed from an airplane (or satellite) on a clear night.

This year's edition of the World Urban Areas Report covers more than a thousand of the largest cities in the world, from Tokyo (pop. 37,000,000), right down to tiddlers like 850th-ranked Leicester (Pop. 534,000): all 1,009 cities, in fact, with a population of half a million of more.

Here are the top 10. See if you can spot any pattern.

 

Seeing it yet? Need a clue?

Okay, here's the same chart again. This time, we’ve coloured the cities by continent.

 

Yep.

Asia's dominance continues as you move down the league tables, too. Here's the top 20:

 

The world's largest continent, in fact, is home to 33 of the world's 50 largest cities, and 50 of the top 100. After that we got bored and stopped counting.

This isn't quite as extreme a result as it may appear: Asia, after all, is home to just shy of 60 per cent of the world's population. So the way in which the 2.1bn people who live in cities of half a million souls or more are distributed around the globe is largely a function of where people actually live. Look:

Comparing those two graphs, you can see that the Americas and Australia are unusually urbanised, Africa unusually under-urbanised, and Europe and Asia are pretty close to what you'd expect.

There are two other striking things about these league tables.

China rules

The first is the dominance of China, which takes 12 places in the top 50, and 22 of the top 100.

Again, this shouldn't be surprising – it's the world's most populous country, home to nearly a fifth of humanity – but nonetheless, it's striking how many of these megacities you almost certainly haven't heard of.

Where power lies

The other striking thing here is how far down the league tables many of the world's most powerful cities fall. Here's where some of the places that commonly make the “world city” league tables fall:

 

Size, it seems, isn't everything.

The data

Here, for completism's sake, is a chart showing the figures for all the city population charts above. You can find the full data set on Demographia's website, here.

Rank City Population
1 Tokyo-Yokohama 37,843,000
2 Jakarta 30,539,000
3 Delhi 24,998,000
4 Maniilla 24,123,000
5 Seoul-Incheon 23,480,000
6 Shanghai 23,416,000
7 Karachi 22,123,000
8 Beijing 21,009,000
9 New York 20,630,000
10 Guangzhou-Foshan 20,597,000
11 Sao Paulo 20,365,000
12 Mexico City 20,063,000
13 Mumbai 17,712,000
14 Osaka-Kobe-Kyoto 17,444,000
15 Moscow 16,170,000
16 Dhaka 15,669,000
17 Cairo 15,600,000
18 Los Angeles 15,058,000
19 Bangkok 14,998,000
20 Kolkata 14,667,000
25 Shenzhen 12,084,000
28 Tianjin 10,920,000
29 Paris 10,858,000
31 Chengdu 10,376,000
32 London 10,236,000
37 Chicago 9,156,000
41 Dongguan 8,442,000
43 Wuhan 7,509,000
45 Hangzhou 7,275,000
46 Hong Kong 7,246,000
47 Chongqing 7,217,000
50 Quanzhou 6,710,000
57 Nanjing 6,155,000
58 Shenyang 6,078,000
59 Xi'an 5,977,000
62 Qingdao 5,816,000
68 Singapore 5,624,000
72 Suzhou 5,246,000
76 Zhengzhou 4,942,000
77 Washington DC 4,889,000
79 Harbin 4,815,000
89 Boston 4,478,000
90 Xiamen 4,420,000
94 Dalian 4,183,000
97 Berlin 4,069,000
99 Fuzhou 3,962,000
101 Dubai 3,933,000
299 Amsterdam 1,624,000
832 Geneva 599,000
 
 
 
 

What can other cities learn about water shortages from Cape Town’s narrow escape from ‘Day Zero’?

Cape town. Image: Pixabay/creative commons.

Cape Town was set to run dry on 12 April, leaving its 3.7m residents without tap water.

“Day Zero” was narrowly averted through drastic cuts in municipal water consumption and last-minute transfers from the agricultural sector. But the process was painful and inequitable, spurring much controversy.

The city managed to stave off “Day Zero,” but does that mean Cape Town’s water system is resilient?

We think not.

This may well foreshadow trouble beyond Cape Town. Cities across the Northern Hemisphere, including in Canada, are well into another summer season that has already brought record-setting heat, drought and flooding from increased run-off.

Water crises are not just about scarcity

Water scarcity crises are most often a result of mismanagement rather than of absolute declines in physical water supplies.

In Cape Town, lower than average rainfall tipped the scales towards a “crisis,” but the situation was worsened by slow and inadequate governance responses. Setting aside debates around whose responsibility it was to act and when, the bigger issue, in our view, was the persistence of outdated ways of thinking about “uncertainty” in the water system.

As the drought worsened in 2016, the City of Cape Town’s water managers remained confident in the system’s ability to withstand the drought. High-level engineers and managers viewed Cape Town’s water system as uniquely positioned to handle severe drought in part because of the vaunted success of their ongoing Water Demand Management strategies.

They weren’t entirely mistaken — demand management has cut overall daily consumption by 50 per cent since 2016. So what went wrong?


Limits to demand management

First, Cape Town’s approach to water management was not well-equipped to deal with growing uncertainty in rainfall patterns — a key challenge facing cities worldwide. Researchers at the University of Cape Town argued recently that the conventional models long used to forecast supply and demand underestimated the probability of failure in the water system.

Second, Cape Town’s water system neared disaster in part because demand management seemed to have reached its limits. Starting late last year, the city imposed a limit on water consumption of 87 litres per person per day. That ceiling thereafter shrunk to 50 litres per person per day.

Despite these efforts, Cape Town consistently failed to cut demand below the 500m-litre-per-day citywide target needed to ensure that the system would function into the next rainy season.

The mayor accused the city’s residents of wasting water, but her reprimanding rhetoric should not be seen as a sign that the citizens were non-compliant. The continuously shrinking water targets were an untenable long-term management strategy.

Buffers are key to water resilience

In the end, “Day Zero” was avoided primarily by relying on unexpected buffers, including temporary agricultural transfers and the private installation of small-scale, residential grey-water systems and boreholes in the city’s wealthier neighbourhoods. The former increased water supply and the latter lowered demand from the municipal system. These buffers are unlikely to be available next year, however, as the water allocations for the agricultural sector will not be renewed and there is uncertainty in the long-term sustainability of groundwater withdrawals.

For more than a decade, Cape Town has levelled demand, reduced leaks and implemented pressure management and water restrictions. This made Cape Town’s water system highly efficient and therefore less resilient because there were fewer reserves to draw from in times of unusual scarcity.

The UN Water 2015 report found that most cities are not very resilient to water risks. As water managers continue to wait for climate change models to become more certain or more specific, they defer action, paralysing decision-makers.

If we really want our cities to be water-resilient, we must collectively change long-held ideas about water supply and demand. This will require technological and institutional innovation, as well as behavioural change, to create new and more flexible buffers — for example, through water recycling, green infrastructure and other novel measures.

Although Cape Town avoided disaster this year, that does not make it water-resilient. Despite the arrival of the rainy season, Cape Town is still likely to face Day Zero at some point in the future.

The ConversationThere’s a good chance that the city is not alone.

Lucy Rodina, PhD Candidate, University of British Columbia and Kieran M. FindlaterUniversity of British Columbia.

This article was originally published on The Conversation. Read the original article.