Density is an issue that's generated heated debate among urbanists — much of it covered here on Cities.
On the one hand, a growing number of economists extol the benefits of greater high-rise construction as a panacea for everything from innovation and job creation to affordable housing. Writing in the pages of The Atlantic in 2011, Harvard's Edward Glaeser points out that "tall buildings enable the human interactions that are at the heart of economic innovation, and of progress itself."
On the other hand, urbanists like Natural Resources Defense Council's Kaid Benfield (also a frequent Cities contributor) as well as the Urban Land Institute's Edward McMahon counter that density can be better achieved "without high-rises." As McMahon noted last year, "one block of an older neighborhood might include a community theatre, a coffee shop, an art gallery, two restaurants, a bicycle shop, 10 music rehearsal studios, a church, 20 apartments and a couple of bars, and all with much more 24/7 activity and intensity of use than one block of (much taller) office buildings."
Here on Cities last year, I pointed out that urban innovation and high-tech start-ups tend not to occur in skyscraper canyons but in mixed-use, mid-rise neighborhoods that spur interaction, like New York's Chelsea and Williamsburg, London's East End, San Francisco's SoMa and Mission District, Venice and Santa Monica in Southern California, and of course Silicon Valley. High-rise districts risk becoming vertical suburbs, as sterile, isolating, and unlivable as sprawl.
That's why a recent report [PDF] from the Urban Land Institute and the Centre for Liveable Cities is so interesting. The diagram below, from the report, arrays the world's great global cities along the key dimensions of density and livability. Density (on the Y-axis) is measured as population per square kilometer and livability (along X-axis) is based on the Mercer's 2012 Quality of Living Survey, which rates cities on factors like public services, transportation, recreation, and their economic, political, and social environments.
This report arrays the world's major cities across four key quadrants. The upper right hand is a "win-win" combination of high density and high livability. The upper left shows high density and low livability. The lower right combines low density and high livability. And, the lower left is the proverbial "lose-lose" of high density and low livability.
Just two cities — London and Singapore — fall into the win-win quadrant of high density and high livability. There are two more which straddle the line — Hong Kong (which hugs the Y-axis of the win-win quadrant) and Tokyo (which hugs the X-axis of that same quadrant). All four of them are among the most expensive cities in the world: density need not be panacea for affordable housing. Contrast this to the many more who fall into the category of high density and low livability.
Many of the world's greatest cities fill the lower right-hand quadrant — Paris, Sydney, Stockholm, Los Angeles and, yes, New York — where low density goes together with high livability. San Francisco, Boston, Washington, D.C., Seattle, Vancouver, and Toronto would also likely fit this segment as well. These cities also number among the world's leaders in innovation and high-tech start-ups. Cities like this which mix densities and uses appear to have a considerable advantage in high-tech innovation and new business creation.
Sadly and dishearteningly, the largest number of cities fill the lose-lose quadrant combining lower densities and lower levels of livability.
The report contains a range of useful suggestions and lessons on how to combine high density and high livability drawn from a detailed case study of Singapore, including: undertaking more systematic planning for long-term growth and renewal, investing in green transportation and infrastructure, drawing nature closer to people, embracing diversity and fostering inclusiveness, and improving the quality of public space overall.
This is especially timely and useful given the massive urbanization that will occur over the next several decades. Hopefully the recommendations in the report can help these rapidly developing cities, especially those in the emerging economies and the "global south" develop more effective approaches to increasing density in ways that can simultaneously spur higher rates of economic development, while improving livability for their rapidly growing populations.