There’s plenty of debate over the future of sustainable urban planning. Is it outer suburban sprawl that’s unsustainable, or is it high-density inner city living that’s at fault?
Brendan Gleeson recently proposed that inner city living is just as unsustainable as the outer suburbs. But let’s check the facts on that.
Professor Gleeson declared:
mounting evidence shows that high density development in inner areas performs very poorly in terms of resource consumption and greenhouse emissions. The idea that outer suburbs are inherently less sustainable than inner ones doesn’t bear scrutiny.
Many readers were surprised by the implication that higher density might actually cause greater emissions. Could something with the evidence have gone awry?
Intuitively, we feel that the outer suburbs are structured around unsustainable and frustrating automotive transport. Outer-suburban living after all requires the equivalent of our body-mass in petrol each week. Dense developments are much likelier to encourage walking, cycling and public transport.
A lot hangs on the claim either way. It matters a great deal to legislation and planning if we believe that greater density improves sustainability or not.
To satisfy readers’ curiosity, Gleeson provided a reference to a recent article of his, “Make No Little Plans”: Anatomy of Planning Ambition and Prospect.
Turning to Gleeson’s article, however, you find that the evidence isn’t very conspicuous.
He quotes another study with similar rhetoric: “In recent years, an accumulating evidence base, including data on revealed consumption, has thrown shadows of doubt over the bright generalisations linking density and sustainability.”
But then when you dig out the article where this quote is from (by Michael Neuman, which has the impressive title The Compact City Fallacy) you find none of the suggested data on consumption and emissions. The only notable empirical evidence in Gleeson’s paper is this:
The 2007 urban consumption analyses produced for the Australian Conservation Foundation (ACF) by the Centre for Integrated Sustainability Analysis at the University of Sydney revealed a consistent geographic correlation between high density and high energy consumption, based on a “full assessment” of (direct and indirect) household energy consumption.
By the author’s own admission, the denser areas are the richer ones. We can explain the higher energy consumption by almost anything except density.
With wealth comes greater luxury and less constrained consumption. Rich people worry less about the setting on their heating, importing designer furniture, and travelling overseas. If I’m rich, I don’t care if I have two or three unoccupied bedrooms, all serviced by central heating and cooling. The relatively lavish pattern of consumption in inner city has no match in the outer suburbs.
The statistics that show inner-city carbon footprints as heavier than the outer-suburb’s reveal nothing about building type, density or planning. They don’t show what kind of development is better for sustainability.
Science isn’t about sets of data. It’s about hypotheses that explain observations by identifying causes. If you can’t distinguish income from density or planning, lots of data just confuses the issue.
Urban planning, like economics, has huge problems attributing statistical patterns to causes. Clearly the attempt in both disciplines is laudable; and nobody is going to call for less scientific ambition. But relying on the level of science that we have so far witnessed to make deep and lasting decisions in urban planning is a mistake. You’d be better off using common sense for the foreseeable future.