If cities are to keep growing, as they will, they must stop growing outwards and start growing upwards. The environmental and human consequences are too great to consider otherwise.
As cities grow, perhaps our most serious concern should be how they expand out into the surrounding countryside. Contrary to popular belief, over the past century urban settlements have not only expanded demographically, they have also sprawled outwards – covering some of the world’s most valuable farmland in the process.
The result has been a steady de-densification of urban settlements, by about –2% per annum. Even where inner-city areas have densified over the past few decades (Copenhagen, for example), the citywide trend is still for an overall reduction in average densities.
In 2010, the total area covered by all the cement, asphalt, compacted clay, park areas and open spaces that comprise the footprint of the world’s urban settlements was around 1 million sq km. In comparison, the total area of France is 643,000 sq km.
If the urban population and long-term de-densification trends continue, the area of the planet covered by urban settlements will increase to more than 3 million sq km by 2050. And since the most intensively cultivated farmland is typically located near where the bulk of the food is consumed, much of this additional 2 million sq km is currently our most productive farmland.
In short, continued urbanisation in its current form could threaten global food supplies at a time when food production is already not keeping up with population growth.
Moreover, density has to be achieved with people in mind, not cars.
Across the world, it would be a mistake to focus solely on improving the average densities of cities. Los Angeles has a higher average density than New York, for example, yet LA is regarded as a dysfunctional urban form while NY is functional, because it comprises a network of high-density neighbourhoods interconnected by efficient and affordable mass transit systems.
Seoul is similar: a megacity that has avoided sprawl with this approach. When the mayor decided to dismantle the eight-lane highway that used to run through the centre of the city, he said: “Seoul is for people, not cars.”
An alternative road was not built – resulting in an increase in the number of people using mass transit which, in turn, made mass transit financially viable. Building more highways for cars, then introducing trains and buses in the hope that they will be financially viable, simply does not work (the greater Johannesburg region is learning that lesson now).
China, meanwhile, has urbanised hundreds of millions of people over the past three decades. This has tended to be in high-rise, multi-storey buildings located in “superblocks” with wide, traffic-congested streets and few intersections per sq km. The result is relatively low densities in neighbourhoods with virtually no street or community life – in short, not the kind of urban area one would call liveable.
Compare this with the neighbourhoods you find in Barcelona, where buildings are five to eight storeys high, located on narrow streets with pavements, trees and small piazzas for social engagement, and all well connected to both motorised and non-motorised forms of transport.
This is what makes for liveable urban neighbourhoods. China has realised its mistake, adopting an urbanisation strategy that breaks away from sprawled-out superblocks in favour of a high-density neighbourhood approach, with narrower streets, a high number of intersections, and improved public transport.
The environmental consequences of suburban living will soon be enormous. On the other hand, what this article does not address is cost. At least in the United States, but also certainly in cities like London, Paris, and, yes, Barcelona, the global Gilded Age has driven the costs of urban living through the roof. To some extent this is the lack of housing supply in a nation like the U.S. that had been disdainful of urban living for most of its history. But it’s also about the size of apartments, the profits for building for millionaires instead of the poor, the global mega-rich owning multiple huge apartments in the world’s cities for their jet-setting lifestyle, etc. It’s not just about building up or density or pedestrian-friendly. It’s about affordability and democracy. If those aren’t values in our cities, then they are no more functional than a model of endless sprawl.