Words by Joey Gardiner
By 2050, the urban population will almost double to 6.3 billion — two-thirds of all the people on the planet. Cities are gaining 77 million new residents each year, equivalent to the population of Turkey or Germany, or twice the state of California. Much of this growth is sprawl. During the first three decades of this century, the global increase in urban land cover is expected to be greater than all urban expansion so far in human history.
Humanity is moving inextricably to cities. For many people, there is only one response: to make cities denser. Adding the threat of climate change just reinforces the argument: dense cities can support the kind of local services and transport infrastructure that gets people out of CO2 emitting cars. Fifty years on from the high-rise social housing experiments that failed so badly, the UN’s “principles for sustainable neighbourhood planning” favour high density. It’s official: density is good for us.
Developers and architects have embraced this new orthodoxy, seizing the opportunity to raise development values with ever more ambitious and complex designs. But urban density is still viewed with suspicion by much of the public, who associate it with rundown 1960s tower blocks, the spectre of Victorian overcrowding, or the nightmare future of Blade Runner’s vertical cities.
Nevertheless, densification must happen or else the world has to sacrifice an unprecedented volume of precious countryside. As Andrew Altman, the masterplanner behind the regeneration of London’s former Olympic Park, now managing principal of Fivesquares Development in Washington DC, says: “We’re going to have to densify, and in terms of the rehabilitation of cities, this is a good thing. But it’s not a choice.”
So, planners, developers and designers are having to consider what higher density should look like, what it will mean for the people living in cities, and how far it can go.
“You can have vertical sprawl. If it’s all high-rise, if it’s not linked to transport networks, if we haven’t learnt to create places that feel humane, then that’s going to be a problem”Andrew Altman, Fivesquares Development
Will increasing density lead us to a more dynamic, wealthier, socially just and environmentally sustainable future? Or will it make the dystopian blight depicted in science fiction into a reality? And if a degree of density is a good thing, is there a point, as we reach further into the sky, at which the benefits start to break down?
How dense is dense?
Across the world, urban density is hugely variable. Statistics on the subject are conflicting and often misleading, depending on how it is measured (in terms of people or buildings), how wide a net is cast around a city, and how much of the less dense suburbs are included. For example, while Manhattan island is seen as a 20th-century benchmark for density, with residential areas reaching 4,250 people per hectare (ha), New York City as a whole is low density by world standards, with just 180 people per ha. Dhaka in Bangladesh is currently rated the highest-density whole city in the world, according to US consultant Demographia, with just under 4,500 people per ha. The city most synonymous with density in the 21st century — Hong Kong — is actually only fourth in global terms, with little over half the population density of Dhaka.
While individual developments can be incredibly dense, what determines the overall figure is how wide an area this extends over. Thus, the perception that high-rise equals high density is often confounded by reality. According to figures from Savills, Kensington & Chelsea, London’s most desirable and expensive borough is also one of its densest, with 135 dwellings per ha, the majority set in low and mid-rise 19th century mansion blocks. In comparison, London’s postwar housing estates were often developed at lower densities than the streets they replaced, with an average of 78 dwellings per ha.
There are many reasons why density is seen as a good thing, but in short it is regarded as more sustainable, in the full sense of the word — environmentally, socially and economically. Cities offer far greater opportunity for the interaction and exchange that generates economic growth. So while they currently house around half of the world’s population, they are, according to the UN, responsible for 80% of global GDP. Greater density puts more people in practical reach of the services that businesses provide. Manila, in the top 20 most packed cities in the world, accounts for 47% of the Philippines’ GDP, despite the fact that it is home to just 12% of the population. In the same way, density gathers together demand for social infrastructure such as hospitals, schools and nurseries, as well as cultural and leisure activities.
Karl Sharro, director at architect and high-rise specialist PLP, and a writer on both urban density and humanism in urban design, has a phrase for the way these benefits spiral upwards: urban intensity. He says: “It’s a social and a cultural thing, where with density you’re able to create more opportunities for informal encounters — for business, for exchange, for art and culture. It tends to increase the intensity of human activity and human interaction.”
The other key argument is environmental. London School of Economics professor Anne Power has estimated that a minimum density of around 30-50 homes per ha reduces dependency on cars by making the provision of public transport viable and effective, while the placing of shops, services and workplaces within walking reach can get people out of motorized transport altogether.
At the heart of the environmental argument is the assumption that high density means less land take. Adam Crozier, director at town planner Barton Willmore, which has masterplanned projects in the UK, the Middle East and Asia, says: “If we are building up rather than out, we’re making a lesser impact on the natural environment around us.”
The book Power wrote with architect Richard Rogers in 2000, Cities for a Small Country, is still a key text here. It argued that doubling the development density in the UK to 50 homes per ha would remove the need to find greenfield land for around 1.5 million homes. Its view that “by living together in close proximity, we can accommodate far more of the world’s population, use less energy, concentrate goods and services, design ecologically sensitive buildings and move around more efficiently” is now effectively the orthodoxy.