As urbanization continues at a rapid pace, it is crucial to investigate its impacts on human and environmental health. Existing literature has produced mixed results and few clear answers.
According to a recently published study, The Lancet Planetary Health It explores the relationship between different urban layouts, human health and sustainability.
study: The impact of urban composition types on urban heat islands, air pollution, and CO2 Emissions and mortality in Europe: A data science approachImage credit: ABCDstock/Shutterstock.com
introduction
Cities are home to 55% of the world’s population, with three out of four Europeans living in urban areas – a proportion expected to rise to 84% by 2050. Urban life offers more services, infrastructure, employment opportunities and social connections.
However, it widens socio-economic disparities and often leads to sedentary lifestyles, with negative health effects.
Cities face challenges such as air pollution, noise pollution, rising temperatures, and limited access to natural spaces. Urban areas create thermal hotspots, known as urban heat islands, and are responsible for 75% of carbon dioxide (CO2) emissions, making them a major contributor to global warming.
Compact City Design
Compact cities pack more people into a smaller space, reducing travel times and distances and encouraging greater use of public transport.
This reduces pollution and lowers the carbon footprint, and shorter distances encourage cycling and walking, making it easier to create social connections and foster a sense of belonging and community.
The effects of urban sprawl
Urban sprawl puts people further away from work, school and entertainment, prioritizing personal transportation and increasing per capita CO2 emissions.
Fragmentation, complexity, rising infrastructure costs and irregular layouts have created discontinuous and disconnected urban spaces, exacerbating socio-economic disparities.
The close relationship between urban composition, sustainability and population health was recognised, revealing that many European cities suffer from poor environmental health, which leads to higher premature mortality.
About the Research
The researchers looked at 919 cities across 31 countries and categorised them into different urban configurations, with the aim of exploring how these relate to environmental exposure, CO2 emissions and health.
The urban configurations were identified based on local climate zones (LCZs) reported in previous studies, which allow for the comparison of cities based on characteristics assessed on a common scale.
European cities were classified into four types according to their urban structure:
- Compact high-density cities (“compact”) are small in size, densely populated cities with little remaining natural areas.
- Low-density green cities (“green”) are larger in size, have lower population densities, and have greater access to natural areas and bike paths.
- Open, low-rise medium-density cities and low-density cities (“open medium-density” and “open low-density” respectively) vary in size and population density but are small or medium in size. Natural area accessibility levels are low or medium.
These were assessed for vehicle traffic flow, surface urban heat island (SUHI) to assess UHI intensity, and air pollution (measured in tropospheric NO2 and CO2 emissions per capita).
What did the study find?
Most of the European cities (261 out of 909) were classified as “less open”. There were almost as many “medium open” (245) and “compact” (246) types. The “green” type was the least represented, with only 167 cities. Interestingly, Mediterranean cities had the highest proportion of “compact” cities.
City centre and suburbs
In most cities, man-made local climate zones (LCZs) were more prevalent in the city center, while natural LCZs were more common in the suburbs. The density of motorways was slightly higher in the suburbs, but other road types were more dense in the city center and gradually decreased towards the suburbs.
Traffic volume, surface urban heat island (SUHI) intensity, and tropospheric NO2 levels were highest in the central area; in contrast, CO2 emissions increased towards the outskirts of the city.
Linkages with sustainability measures
Compared to other types, “compact” and “open medium-sized” cities showed higher vehicle traffic volumes in all LCZs and all concentric zones.
However, the two types were similar in terms of traffic volume and had high levels of exposure to NO2.
The majority of the urban population was concentrated in “compact” or “open medium-sized” cities.
“Compact” cities, with easily accessible amenities, better traffic management and opportunities for walking and cycling on dedicated networks, were shown to have the lowest CO2 emissions.
However, “compact” cities also have much lower CO2 emissions per capita than “green” cities.Urban sprawl increases complexity, disorder and fragmentation, and reduces spatial connectivity and continuity.
“Green” cities had higher SUHI intensity than any other type of city. However, “compact” cities had lower SUHI intensity than “open medium” or “open low” cities. Among the latter, “open low” cities had lower SUHI than other cities outside the city center.
“Green” cities had the lowest mortality rates and best environmental health conditions compared to all other types of cities.
Conclusion
The study suggests a clash between sustainability and health: the compact city configuration is in theory the optimal, healthiest and most sustainable urban model. However, compact cities have very poor environmental quality and do not meet health standards.
High density means more polluted areas and less natural space. Automobile traffic dominates, negating theoretical benefits like sidewalks, bike paths and proximity to amenities.
Small, sparsely populated cities are probably better off as they are. In contrast, compact cities could be healthier with improved long-distance transport, less traffic and more green public spaces, such as sky gardens, street trees, and small gardens wherever possible on the grounds of houses, factories, schools, universities, and institutions. However, this could drive up real estate costs and increase inequality.
This means thatTo promote environmental and climate justice, it is important for urban planners to monitor the environmental quality, accessibility, and equitable distribution of these spaces..”
In large, sprawling or rapidly growing cities,Measures such as densification, service provision, and appropriate mix [residential and non-residential] The buildings will help create a denser, more diverse neighborhood with cultural, social and employment opportunities..”
“Contemporary European Compact Cities [are] They are in a transitional period where positive aspects such as access to services and reduced carbon emissions are combined with challenges such as increased traffic and poor environmental quality. Cities are complex systems and solutions require a holistic approach..”