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Thoughts about the relationships between transport and the urban area it serves

Archive for January 7th, 2014

“Beefing Up Population Density Won’t Curb Greenhouse Gas Emissions”

with 4 comments

I have put the headline in quotation marks as it does not reflect  my opinion – nor does it seem to be based on a very reliable way of forecasting policy outcomes. The headline comes from Atlantic Cities but the research itself is published in Environmental Science and Technology. The title there is “Spatial Distribution of U.S. Household Carbon Footprints Reveals Suburbanization Undermines Greenhouse Gas Benefits of Urban Population Density” (citation shown at foot of this article). And of course you and I do not have the right credentials to actually read this on line unless you are willing to pay a very hefty fee. But at least Berkeley provides a longer item than Atlantic Cities does and this is where their quotes are lifted from

As you will note, other readers have already taken exception to the conclusions that are quoted by Atlantic Cities, so I am not alone at being troubled by the attention getting headline. Because it does not seem to be adequately supported. I also am troubled since I have been advocating and teaching the exact opposite for many years now. First as part of the Community Energy Planning activities of the BC Energy Aware Committee – now the Community Energy Association – and latterly as part of a program for  people wanting to become Sustainable Building Advisors under the the LEED program, sponsored by the Canada Green Building Council. The thrust of my message has been – and still is – the putting up the greenest building possible is not going to achieve emission reductions if you put it in the wrong place and everyone has to drive to get there. Sure the building itself may perform flawlessly but the trips the building’s activities generate will more than make up for the energy savings achieved over more conventional technologies.

Denser urban areas do indeed perform far better – in terms of energy consumption and hence reduce greenhouse gas emissions – than less dense ones, and that is exactly what the maps that accompany the article show.

carbon denver

This just happens to be Denver – and you can also see the smaller city of Colorado Springs off to the left (west) which shows the same doughnut ring pattern of carbon emissions. And they do observe “large metropolitan areas have a slightly higher average carbon footprint than smaller metro areas.” But that may just be that in the US (and the data they use only comes from there) the larger metro areas have proportionately more suburbs.

People who live in denser urban areas do not need to make as many trips by single occupant motor vehicles as those who live in less dense areas. People who work in city locations are much less likely to have drive during their work hours than those in suburban office parks. If you can get what you need within a short walk then you are less likely to need to drive. In places like downtown Vancouver, the vehicle most likely to be used for most trips is the electric elevator. Moreover building technologies and simple physics favour denser areas notably when the designers are thinking holistically. Community energy systems are more efficient than individual systems. The village on False Creek, for instance, gets some of the heat for its buildings from the sewers. Many buildings in city centres need more cooling than heating, so careful siting and interconnectedness produces a better overall outcome than locating them at greater distances where this is not efficient in economic or energy terms.

But there are also all sorts of other benefits from greater densities. Indeed density in and of itself may not be the answer. Better density – the right kind of density – is almost always going to have better results no matter what metric you use. We happen to be concerned in this case with reducing greenhouse gas emissions but exactly the same responses work if you are looking to create a happier human environment, or one that preserves land for food production or recreation, or reducing traffic congestion, or cutting public expenditures. The arguments made by Charles Marohn for Strong Towns are almost entirely financial.

Actually I think what is really at play here is Atlantic Cities looking for a headline rather than better understanding. What the researchers are actually saying is that there is no one size fits all solution and that increasing density does not of itself produce the best outcomes. But it is also clear that continuing with business as usual, widening freeways and building new ones, refusing to invest in transit, sticking with strategies that favour “drive until you qualify” suburbs and so on is a recipe for disaster. And increasing density is often going to be a significant part of the solution.

citation

Christopher Jones *† and Daniel M. Kammen *†‡§
†Energy and Resources Group, ‡Goldman School of Public Policy, and §Department of Nuclear Engineering, University of California, Berkeley, California 94720, United States
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es4034364
Publication Date (Web): December 13, 2013
Copyright © 2013 American Chemical Society
*Phone: (510) 643-5048. E-mail: cmjones@berkeley.edu., *Address: Renewable and Appropriate Energy Laboratory, University of California, Berkeley, CA 94720-3050. Phone: (510) 642-1640. Fax: (510) 642-1085. E-mail: kammen@berkeley.edu.