Where are the world's largest cities?

An astronaut's eye view of urbanisation. Image: Getty.

Every year or so, Demographia, the St. Louis-based consultancy, publishes the World Urban Areas Report – a sort of bumper book of city population stats.

The report is a veritable treasure trove of demographic stats for city nerds. If you want to know whether, say, Edinburgh is one of the 1,000 biggest cities in the world, then Demographia will tell you. (It's not, it's just outside at joint 1017th). And if you want to know whether Paris covers a bigger land area than London, it'll tell you that, too. (It does: 2,845km2, as opposed to 1,738 km2.)

It even includes estimates for the size and density of hundreds of towns so tiny that you're slightly surprised to find that anyone on the other side of the Atlantic has even noticed they exist. (Favourite example: Kidderminster*.)

But the most fun is to be found in the first half of the report. Table 1 includes the 1,022 built-up areas in the world that house 500,000 people or more, ranked in order of population; Table 2 ranks the same cities in order of land area.

I don’t know about you guys, but we are stoked.

via GIPHY

(*55,000 people in 16 km2, giving a population density of 3,400 per km2, since you ask.)

Understanding the numbers

Explanations first. The report defines urban areas as

...a continuously built up land mass of urban development that is within a labour market (metropolitan area or metropolitan region)... [and] contains no rural land.

We should probably also note the reports caveat, about the limits of its own methodology:

Revisions are made as more accurate satellite photographs and population estimates become available. As a result, Demographia World Urban Areas is not intended for trend analysis.

Year-to-year changes indicated in population and land area may merely reflect better data that was not used before and may not, therefore indicate a trend.

In other words, if this year's report has a larger estimate for a city's population than last year's report, that might mean the city has grown. Then again, it might just mean that new, more accurate data has appeared.

Moreover, nearly all of the data is estimated. Appropriate caution is therefore advised.

Spoilsports.

The biggest cities, by counting people

Anyway, let’s get to the fun bit. Here are the 10 largest cities in the world by population:

It’s pretty familiar stuff. The top 10 is dominated by Asian cities, with a strong showing from New York City. Tokyo is far in the lead, with Jakarta and Delhi coming up behind. For anyone who pays any attention to this stuff, there aren't at first glance any massive surprises.

We're not supposed to compare with last year's figures for all the reasons laid out above, but what the hell, here's the 2015 top 10:

There are two big differences worth noting. One is that only one Chinese city is now in the top 10, down from three last year. (Beijing and Guangzhou are now ranked 11th and 13th.) All three have seen their populations revised downwards: this seems to the result of previous over-estimates, rather than mass evacuations.

The other noteworthy trend is the sudden appearance in the top 10 of Mumbai, with nearly 23m people. Last year, it ranked 13th with 17.7m. In a section headed "Revised data: highlights", the report notes:

The Mumbai built-up urban area has been expanded to incorporate the Bhiwandi, Kalyan and Vasai-Virar urban areas.

In other words, it isn't that a population the size of Madrid has moved to Mumbai over the last year. Rather, it's become clearer that the megacity has expanded to swallow surrounding areas.

You can see why ranking cities is a complicated business.

The biggest cities, by measuring land

As noted, most of the biggest cities in the world by population are in Asia. Most of the biggest cities in the world by physical size are, well, somewhere else.

Suddenly, with the single exception of Tokyo, Asia doesn’t even feature. Eight out of 10 are in the US. Atlanta has an estimated 5.1m residents, so measured by population it’s the 79th largest city in the world. Measured by land area, though, it ranks fourth.


I guess this is what happens when you build your cities around the car.

Incidentally, the report estimates Atlanta's population density to be 700 people per km2. The comparable figure for Dhaka in Bangladesh – 16.2m people, the 16th largest city in the world - is 44,100.

Dhaka is 63 times more crowded than Atlanta.

All the megacities

One more chart: this is the top 36 by population.

The reason we've stopped at that arbitrary point is not to get London into the rankings (well, not only for that reason). It's because the common definition of megacity is that with a population over 10m.

This is all of them. We've colour coded them by continent:

That's three each in North America, South America, Europe and Africa.

But the remaining 24 – two thirds of all the world's megacities – are in Asia. Five of them are in China alone.

Here, because we love you, is the data used in that graph. Enjoy.



Rank City Population
1 Tokyo-Yokohama 37,750,000
2 Jakarta 31,320,000
3 Delhi 25,735,000
4 Seoul-Incheon 23,575,000
5 Manila 22,930,000
6 Mumbai 22,885,000
7 Karachi 22,825,000
8 Shanghai 22,685,000
9 New York City 20,685,000
10 Sao Paulo 20,605,000
11 Beijing 20,390,000
12 MexicoCity 20,230,000
13 Guangzhou-Foshan 18,760,000
14 Osaka-Kobe-Kyoto 16,985,000
15 Moscow 16,570,000
16 Dhaka 16,235,000
17 Cairo 15,910,000
18 Bangkok 15,315,000
19 Los Angeles 15,135,000
20 Kolkata 14,810,000
21 Buenos Aires 14,280,000
22 Tehran 13,670,000
23 Istanbul 13,520,000
24 Lagos 12,830,000
25 Shenzhen 12,240,000
26 Rio de Janeiro 11,815,000
27 Kinshasa 11,380,000
28 Tianjin 11,260,000
29 Lima 10,950,000
30 Paris 10,870,000
31 Chengdu 10,680,000
32 Lahore 10,355,000
33 London 10,350,000
34 Bangalore 10,165,000
35 Ho Chi Minh City 10,075,000
36 Nagoya 10,035,000

 

And if you want more of this stuff, here’s our report on the 2015 edition of the Demographia World Urban Areas Atlas.

Jonn Elledge is the editor of CityMetric. He is on Twitter, far too much, as @jonnelledge.

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Here’s how we plant 2 billion more trees in the UK

A tree in Northallerton, North Yorkshire. Image: Getty.

The UK’s official climate advisor, the Committee on Climate Change (CCC), recently published a report outlining how to reduce the 12 per cent of greenhouse gas emissions that come from land use by two thirds by 2050. Alongside recommending cutting meat and dairy consumption by 20 per cent, the report calls for the annual creation of up to 50,000 hectares of broadleaf and conifer woodland for the next three decades. This would increase forest cover from 13 per cent to at least 17 per cent – a level not seen in Britain since before the Norman invasion.

Reforestation at that rate would mean creating roughly the area of the city of Leeds every year for the next three decades. At typical stocking densities of 1,500 stems per hectare, the ambition is to establish some 2.25 billion additional trees. Given that the UK, as with most of Europe, is in the grip of ash dieback, a disease likely to prove fatal for many millions of native ash trees, the scale of the challenge is massive.

On a crowded and intensively farmed island like Britain, unlocking a million and a half hectares of land will be no mean feat. But it’s not impossible – and is an unprecedented opportunity not only to tackle the climate crisis but also the biodiversity crisis that is every bit as detrimental to our wellbeing.

Trees and farms

One million and a half hectares is just 6 per cent of the mainland UK’s land area. To give some sense of perspective on this, 696,000 hectares of “temporary grassland” were registered in 2019. So if land supply is not the problem, what is? Often it’s cultural inertia. Farmers are firmly rooted to the land and perhaps understandably reluctant to stop producing food and instead become foresters. But the choice need not be so binary.

The intensification of agriculture has caused catastrophic declines in many species throughout the UK by reducing vast wooded areas and thousands of miles of hedgerows to small pockets of vegetation, isolating populations and making them more vulnerable to extinction.

Integrating trees with the farmed landscape delivers multiple benefits for farms and the environment. Reforestation doesn’t have to mean a return to the ecologically and culturally inappropriate single-species blocks of non-native conifers, which were planted en masse in the 1970s and 1980s. Incentivised under tax breaks to secure a domestic timber supply, many of the resulting plantations were located in places difficult or in some cases impossible to actually harvest.

Productive farmland needn’t be converted to woodland. Instead, that 4 per cent of land could be found by scattering trees more widely. After all, more trees on farmland is good for business. They prevent soil erosion and the run-off of pollutants, provide shade and shelter for livestock, a useful source of renewable fuel and year-round forage for pollinating insects.

The first tranche of tree planting could involve new hedgerows full of large trees, preferably with wide headlands of permanently untilled soils, providing further wildlife refuge.


Natural regeneration

Where appropriate, new woody habitats can be created simply by stopping how the land is currently used, such as by removing livestock. This process can be helped by scattering seeds in areas where seed sources are low. But patience is a virtue. If people can learn to tolerate less clipped and manicured landscapes, nature can run its own course.

A focus on deliberate tree planting also raises uncomfortable truths. Most trees are planted with an accompanying stake to keep them upright and a plastic shelter that protects the sapling from grazing damage. All too often, these shelters aren’t retrieved. Left to the elements, they break down into ever smaller pieces, and can be swept into rivers and eventually the ocean, where they threaten marine wildlife. Two billion tree shelters is a lot of plastic.

The main reason for using tree shelters at all is because the deer population in the UK is so high that in many places, it is all but impossible to establish new trees. This also has serious implications for existing woodland, which is prevented from naturally regenerating. In time, these trees will age and die, threatening the loss of the woodland itself. Climate change, pests and pathogens and the lack of a coordinated, centrally supported approach to deer management means the outlook for the UK’s existing treescape is uncertain at best.

An ecologically joined-up solution would be to reintroduce the natural predators of deer, such as lynx, wolves, and bears. Whether rewilding should get that far in the UK is still the subject of debate. Before that, perhaps the focus should be on providing the necessary habitat, rich in native trees.

A positive response would be to implement the balanced recommendations, made almost a decade ago in a government review, of creating more new habitat, improving what’s already there, and finding ways to link it together. Bigger, better, and more connected habitats.

But the UK is losing trees at increasing rates and not just through diseases. The recent removal of Victorian-era street trees in Sheffield and many other towns and cities is another issue to contend with. As the climate warms, increasing urban temperatures will mean cities need shade from street trees more than ever.

Trees aren’t the environmental panacea that the politicians might have people believe – even if they do make for great photo opportunities – but we do need more of them. Efforts to expand tree cover are underway across the world and the UK will benefit from contributing its share. Hitting the right balance – some commercial forestry, lots of new native woodland and millions of scattered trees – will be key to maximising the benefits they bring.

Nick Atkinson, Senior Lecturer in Ecology & Conservation, Nottingham Trent University.

This article is republished from The Conversation under a Creative Commons license. Read the original article.