Polarizing evidence of the connection between compact city and carbon footprints

Compact cities are expected to reduce greenhouse gas emissions. Reduced automobile dependency and short distances result in lower driving related emissions. Some studies have also suggested lower emissions from housing energy, due to smaller apartments. At the same time, dense urban areas are associated with agglomeration economies. Increasing population correlates with the increasing productivity of a city. Furthermore, population and dense urban areas also correlate positively with wages and housing prices. This is interesting from the greenhouse gas perspective, since income is the main driver of a person’s carbon footprint, and economic growth the main driver of global GHG emissions.

This paper illustrates how the compactness of a city is connected to the GHG emissions from transport and housing, income and total carbon footprint of the residents of the city. The study includes 20 largest cities in Finland. The carbon footprints are calculated with an environmentally extended input output analysis based hybrid life cycle assessment method. Regression analysis is utilized to test the impact of various compact city related variables, including population, population density, population living in the inner urban area of the city and the share of the population living in the inner urban area. The results of the study demonstrate that income is best explained by the population of the city, which is associated with all the other compact city variables. However, the share of the population living in the inner urban area explains better the total carbon footprint. All the compact city variables correlate positively with carbon footprint, when income is not controlled, but assumed to be driven by the same variable. However, the emissions caused by motor fuel consumption decrease with increasing density, regardless of which compact city variable is used. At the same time, the emissions caused by other travel, including public transport and holiday travel, increase.

More research is needed to elaborate, whether compactness of a city or avoidance of urban sprawl alone have any impact on productivity and income, or if all these variables are simply driven by the population, or other variables omitted here. However, if we wish to build compact cities specifically for the possible economic benefits, we have to understand that this is in contradiction with the environmental goals.