A new study of 919 European cities found that small cities with a high population density are not only less green than low-density urban areas, but they also have worse air quality (due to higher nitrogen dioxide emissions from vehicles) and higher mortality rates.
The findings, published in The Lancet Planetary Health, further highlight that while compact-sized European cities have significantly lower carbon emissions, their drawback is that they have less green space which makes residents far more vulnerable to stronger urban heat island effects. “However, sprawled cities with low population density also face challenges, particularly related to larger travel distances, higher CO2 emissions, car dependency, availability of proximal and diverse destinations, and social isolation,” the authors highlighted.
Because cities are mostly concrete jungles and every surface is covered under concrete or asphalt, they absorb and retain more heat during summer and become hotter than rural areas. The only way to combat the urban heat island effect is to increase green areas like parks, and gardens, and protect and plant more street trees.
“Compact cities have many conceptual benefits in terms of reduced car dependency, walkability, proximal access to services, increased social interactions, and an increased sense of community,” the authors wrote in the study. “Yet, in their current configuration, they are highly densified and probably act as economic hubs that attract large numbers of commuters for education or employment opportunities. In addition, mobility within compact cities is still, to a large extent, reliant on motorized transport modes.”
“As revealed by our analysis, traffic volume is considerably higher within the compact city type compared with all other urban configurations, which is also in line with the higher nitrogen dioxide emissions observed among these cities,” they added. “In this sense, current European compact cities should be understood as being in a transition state towards an optimal form, a state that currently combines some positive features (such as proximity to services) with challenges such as densification, mobility, management of traffic flows, poor air quality, and insufficient green and natural spaces.”
One of the lead authors, Tamara Iungman, a researcher at ISGlobal, and colleagues suggested a few measures that could help make compact cities less polluted and cooler for residents.
They explained that in terms of density, there should be a maximum of 175 dwellings per hectare. That way, people will not feel socially isolated and can still create a sense of community while living in a walkable city with easy access to essential services. The authors said promoting high-quality public transportation and reducing reliance on cars could help reduce traffic and air pollution levels. One solution that they say will have immense health benefits is to have car-free neighborhoods in big cities.
“Compact cities can be leveraged for implementing new urban models that promote the creation and better use of public spaces for citizens. These approaches include the implementation of superblocks in various parts of Barcelona, Spain, the development of low-traffic neighborhoods in London, and the creation of car-free neighborhoods in Hamburg and Freiburg, with potential positive effects for the environment and health,” the authors wrote.
Integrating green spaces while planning infrastructure projects is another crucial solution that more urban areas can adopt.
“Green roofs or façade greening can be introduced in highly sealed commercial areas to reduce surface water runoff. Sky gardens can compensate for the absence of ground-level green spaces; street trees mitigate CO2 emissions and improve the microclimate; and the introduction of small gardens in public, industrial, educational, and institutional spaces can contribute to supporting biodiversity as part of areas of green spaces in the city,” they added.
