The ideal compact city model for the environment shows higher mortality rates

A compact city is characterized by concentrating more population in less space by means of large buildings. This is the case of Barcelona, ​​Paris or Basel. Theoretically, this type of urban planning, common in old Mediterranean cities, is more efficient, shortens travel distances and encourages getting to places on foot or by bike. The opposite model is that of cities that occupy large areas with a reduced density, such as Helsinki, Rennes or Stockholm. These usually have more green areas, but they also increase dependence on private cars and create more distances between neighbors. For all these reasons, in Europe it is often considered that the compact city is the optimal design to promote healthier and more sustainable urban planning. Or at least that is the theory. A study now published in The Lancet Planetary Health, Based on real data from 919 European cities, the study found that denser cities do have a smaller environmental footprint, but they also expose people to poorer air quality and a greater heat island effect, leading to higher mortality rates. In compact cities, the average is 1,124 non-accidental deaths per 100,000 inhabitants per year, compared to 1,003 deaths in lower-density cities.

“It was actually a surprise. We expected that there would be lower mortality rates in compact cities because we thought that people would do more physical activity by walking,” said Mark Nieuwenhuijsen, lead author of the study and researcher at the Barcelona Institute for Global Health (ISGlobal), an entity promoted by the La Caixa Foundation that has led the scientific work. As he explains, it is one thing for the design of these cities to allow people to walk more or use public transport more, and another for citizens to actually use their private cars less. “There are still a lot of cars in these cities, which causes a lot of air pollution and takes up a lot of space that could be used for green areas,” Nieuwenhuijsen emphasises.

The research analyses 919 European cities, classifying them in four different ways: high-density compact cities, low-rise open cities with medium density, low-rise open cities with low density and low-density green cities. The results confirm that compact cities with higher population density generate lower CO₂ emissions per capita, given that travel distances are shorter and the services used by citizens (waste collection, water, electricity, etc.) can be provided more efficiently.

However, these cities also have higher levels of air pollution and a greater heat island effect, as well as a higher mortality rate. On the other hand, low-density cities with low-rise housing and more green areas are worse for the environment in terms of per capita emissions, as they require more private car use and generate longer distances. On the other hand, they show better indicators in air quality, heat island effect and mortality.

Cities are of great importance to the environment, as 55% of the world’s population now lives in urban areas, a percentage that reaches 75% in Europe. It is from these spaces that the greatest amount of resources (energy, water, materials, food…) are demanded. In fact, urban areas are behind 75% of the global emissions that cause the climate crisis. Thus, how these urban spaces are designed can translate into a significant increase or reduction of the human footprint on the planet as a whole.

Despite the results of this study, the researchers of this work continue to consider the compact city as the most appropriate, since they consider that from a conceptual point of view they have important benefits, such as reducing dependence on cars, increasing physical activity, bringing access to services closer, increasing social interactions or reinforcing the feeling of community. However, they also emphasize that compact cities must overcome a transition so that these theoretical advantages are translated into real results in air quality or mortality.

“It is the best model for a city,” Nieuwenhuijsen stresses. “Most of the population lives in compact cities, there are fewer CO₂ emissions per capita, there is more public transport, people use bicycles more. Of course, the problem is the levels of air pollution and there are fewer green spaces, but it is easier to change compact cities to make them healthier than to try to transform cities with lower population density to make them denser,” the researcher stresses. The study recommends improving public transport to reduce the use of private cars and promoting some innovative city designs such as the superblocks in Barcelona, ​​the slow-traffic neighbourhoods in London or the car-free neighbourhoods such as Freiburg. In this regard, although the study does not mention it, the delay in Spanish cities to implement low-emission zones is noteworthy.

Of the 919 cities analysed, the majority of the population resided in high-density compact cities (68 million people) and low-rise, medium-density open cities (56 million), compared to low-rise, low-density open city types (38 million) and low-density green cities (27 million).

Although the study links mortality rates to air pollution, the existence of green spaces or the heat island effect, the study itself warns that other possible factors such as socioeconomic level, population habits or healthcare services have not been taken into account. “The cities analysed are fairly well distributed across Europe, so this should not be a major problem, but it is clearly a limitation to take into account,” Nieuwenhuijsen acknowledges. “We know that socioeconomic level is very relevant to mortality, there can be a difference of 10 years in life expectancy between poor neighbourhoods and rich ones, but there is no good data on this aspect to be able to include them.”

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