Helsinki, one of the two major metropolitan areas studied in Finland.
A recent study published at Environmental Research Letters challenges the commonly held belief that high-density urban areas produce fewer carbon emissions per capita than less dense rural areas.
Analyzing the carbon footprint of eleven urban areas in Finland’s two largest metropolitan areas, Jukka Heinonen and Seppo Junnila of Aalto University found that population density had a low, if not insignificant relationship to carbon emissions per capita. Instead, they found level of income, and its corresponding level of consumption, to be the more significant factors.
What sets this study apart from most previous research is the particular hybrid life cycle assessment methodology Heinonen and Junnila employed.
Life cycle assessment (LCA) attempts to assign the carbon footprint of producing, transporting, maintaining and disposing of a good or service to the consumer. For example, the environmental impact of manufacturing a piece of furniture in a rural factory is not attributed to the factory, but to the consumer who purchases the item. The logic behind LCA is straightforward: the amount of carbon emissions a factory produces is directly related to the amount of goods or services it produces, which in turn is determined by consumer demand. No demand, no emissions.
The data Heinonen and Junnila used was comprised of nearly 1,000 consumption categories, which they collapsed into 43 classes, and later, 10 consumption areas: heat and electricity, building and property, maintenance and operation, private transport, public transportation, consumer goods, leisure goods, leisure services, travel abroad, and health nursing and training services.
As with previous studies, the researchers observed lower carbon emissions in higher density areas associated with housing type (apartment buildings vs detached structures), higher reliance on public transportation and lower dependence upon private transportation.
However, carbon impact attributable to these categories varied less than expected with differences in population density; moreover, those differences were more than offset by greater consumption of goods and services in higher income, higher-density areas.
Whether the methodology employed by Heinonen and Junnila would produce similar results when applied to other urban-rural studies remains to be seen. In the U.S., for example, carbon emissions due to transportation are significantly higher than in Europe.
The larger point of the study, however, remains: any effort to lower carbon emissions must include those related to income and consumer consumption.
