New research from University of California, Berkeley, shows that, based on econometric modelling, households in the suburbs surrounding US large cities have a household carbon footprint that is significantly larger than that of households in the more dense city centres. That larger household carbon footprint is primarily the result of consumption of energy, transportation, food, goods and services. The primary drivers of household carbon footprints are household income, vehicle ownership and home size, all of which are considerably higher in suburbs.

That suburbs have a higher household carbon footprint based on these measures should be no surprise. People who live in highrise apartments and high density street level homes frequently access daily needs, workplaces, and schools more efficiently than those who live in the sprawl. It should be noted that the study is based on economic models, not measurements which are difficult for greenhouse gas emissions, and that it does not sufficiently consider the carbon sequestration effects of biomass in the suburbs. Despite these limitations, GallonDaily sees no need to doubt the overall findings.

The authors urge that these data should be taken into account when planning GHG mitigation efforts. They state that increasing population density alone, either in the inner city or in the suburbs, appears not to be a very effective strategy for reducing emissions. They state that a 10-fold increase in population density in central cities corresponds to only 25 percent lower greenhouse gas emissions, and population dense suburbs have significantly higher carbon footprints than less dense suburbs, due largely to higher incomes and resulting consumption.

The project team has developed and published a tool that calculates carbon footprints for essentially every populated U.S. zip code, city, county and U.S. state as well as an interactive online map allowing users to zoom in and out of different locations. Households and cities can calculate their own carbon footprints to see how they compare to their neighbours and create customized climate action plans from over 40 mitigation options. What a shame that no similar tool is available for cities and towns in Canada.

The authors argue that cities need to step out of traditional roles in planning urban infrastructure and learn how to better understand the needs of residents in order to craft policies and programs that enable the adoption of energy and carbon-efficient technologies and practices. They claim that when you package low-carbon technologies together you find real financial savings and big social and environmental benefits.

This type of analysis is likely to have a big impact in future as states, provinces and municipalities become more engaged with GHG emissions reduction. GallonDaily surmises that cities of the future may become much more clusters of urban communities rather than urban centres surrounded by suburbs. Maybe employers in future will draw their employees much more from the immediate community rather than from across the urban sprawl.  Data such as that compiled by this research team will almost certainly play an important role in the evolution of urban areas.

An extended abstract of the UC Berkeley research and a link to the household carbon footprint calculator and mitigation tool is available at http://newscenter.berkeley.edu/2014/01/06/suburban-sprawl-cancels-carbon-footprint-savings-of-dense-urban-cores/

The research paper (fee or subscription required) and an academic abstract are available at http://pubs.acs.org/doi/pdf/10.1021/es4034364