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Carbon footprints: What you buy matters, but where you live is more important!

Dan Hoornweg's picture

Lots of people, companies, cities, and nations have started to calculate their greenhouse gas (GHG) emissions, since you can only change what you can measure. These measurements are starting to highlight some very interesting trends and show how complex the global results of our lifestyle are.

In a recent paper Lorraine Sugar and I prepared on GHG emissions, with detailed neighborhood information for the City of Toronto (from University of Toronto researchers VandeWeghe and Kennedy) we highlighted that what you buy is important in determining your GHG emissions, but where you live is much more important. The three neighborhood images, all in the Toronto region, show how urban form is the most important determinant of your carbon footprint.

The neighborhood of East York has the lowest per capita emissions (1.3 t). It is an area with high-density apartment complexes that are within walking distance to a shopping center and public transit.

Etobicoke has medium GHG emissions per capita (6.62 t). It is a neighborhood of high-density single family homes close to the city center and accessible by public transit.

The neighborhood of Whitby has the highest per capita emissions (13.02t)—it’s located in the suburbs of Toronto with large, low-density single family homes that are distant from commercial activity and public transit.

The affluence of the three neighborhoods is roughly equal, however when where you live is relatively dense, well served by public transport, and many destinations are within walking distance, per capita GHG emissions can be much lower. The three neighborhoods are all within the Metropolitan Toronto area, yet per capita emissions vary by an order of magnitude.

Emission reductions brought about by banning shopping bags, buying organic food, or even encouraging more fuel efficient vehicles or higher rates of renewable energy, although important, will never yield an impact similar to what can be brought about by living in better designed, better served, and healthier neighborhoods.

The numbers associated with the Toronto neighborhoods above are only for residential emissions, and may not include other lifestyle impacts such as emissions from employment and international travel, which are also important contributors to GHG emissions. However these numbers do highlight the dramatic importance that urban form has on our per capita greenhouse gas emissions. This information is part of a paper submitted to Environment and Urbanization.

Looking at per capita GHG emissions is complicated, especially when you include all emissions within a city. For example, if a city has a major shipping port or airport, emissions will be relatively high. Or, if there is a high concentration of industry within the city limits, emissions will be higher. Availability of hydropower reduces emissions. Although calculating emissions can be difficult, city planners and policy analysts can only begin to build better cities when good, disaggregated information is available.

In an upcoming blog, we will look at the variation in per capita GHG emissions across Canada and why this is important for cities everywhere.

 

Comments

Interesting story but it also points to the exclusions from the analysis including employment travel and influence of industry location. To live in relatively dense population centres, well served by public transport, with many destinations within walking distance may well reduce per capita GHG emissions ... but only because that's the way it's been measured. Are all the emissions associated with the infrastructure of these ideal dense poulation centres included? Maybe the locations that support these ideal centres (that is, the ports and industrial centres) should be given credit for the savings they generate for people who dont have to produce food, materials, electricity, water etc?.

Good point David. Yes, the analysis is limited and caution is needed when looking just at these numbers. For example if someone living in the lower GHG emitting neighbourhood flies for more than 40 hours a year their overall emissions would be higher than someone living in the more spread-out neighbourhood (assuming that they did not fly). Other things like seasonal (second) homes, family size, and type of employment and hobbies will also have a big impact on total overall emissions. The comparison of neighbourhoods is more of a place to start. Regards, Dan

Submitted by Sameer Akbar on
Remember 'Ecological Footprint' for cities ( en.wikipedia.org/wiki/ Ecological _ footprint ) ? Well that was not too long before 'Carbon Footprint' came along. However, the challenges are not too different. It is most important to be clear and transparent about 'what' , 'how', and 'why' the assessment is being made. It is often unclear what the carbon footprint is assessing. Is it the "gross" or "absolute" emissions, or is it the "net" or "relative" emissions ? While the former is really the footprint, the latter is a measure of the impact of an intervention, with respect to a counterfactual scenario. However, it is important to clearly define the intervention. The boundary of an intervention may vary depending on it nature and scale. For example, a new urban road may affect the whole network of roads in a city and hence have major indirect impacts in terms of carbon emissions, as compared to replacing pump sets at the municipal waste water treatment facility. In the parlance of GHG accounting this opens up the question of scope 1, 2 and 3 emissions - as defined by the GHG protocol (www.ghgprotocol.org) How the counterfactual scenario is defined can affect the assessment significantly ; and this relates to how the baseline or business-as-usual scenario is defined. The baseline could be considered "static" or "dynamic"? While the former assumes that without intervention the scenario would continue to be the same as before the intervention, the latter assumes changes that would occur over the time period of assessment. The time period could range from an average year of operation / implementation to the economic lifetime of the intervention; or even the time frame of loan repayment, if externally financed. Finally, the question boils down to why the footprint is being assessed. Is it to account for emissions or analyze the impact of interventions? While the former would call for a gross or absolute assessment, the latter requires the assessment of net or relative emissions.

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