With the rapid pace of urbanization, it's crucial to investigate its impact on human and environmental health. The existing literature offers mixed results, providing little clarity.
A recent study published in The Lancet Planetary Health examines the relationship between different urban layouts, human health, and sustainability.
Study: The impact of urban configuration types on urban heat islands, air pollution, CO2 emissions, and mortality in Europe: a data science approach. Image Credit: ABCDstock/Shutterstock.com
Introduction
Cities are home to 55% of the world's population, with three out of every four Europeans living in urban areas, a proportion expected to rise to 84% by 2050. Urban life provides more services, infrastructure, job opportunities, and social connections.
However, it also amplifies socioeconomic disparities and often leads to sedentary lifestyles, adversely affecting health.
Cities face high levels of air and noise pollution, higher temperatures, and limited access to natural spaces. Urban areas create thermal hotspots known as heat islands and are responsible for 75% of carbon dioxide (CO2) emissions, significantly contributing to global warming.
Compact City Design
Compact cities pack more people into smaller spaces, reducing travel times and distances and promoting the use of public transport.
This leads to less pollution and a smaller carbon footprint. Short distances encourage cycling and walking, making social connections easier and fostering a sense of belonging and community.
Effects of Urban Sprawl
In sprawling cities, larger distances separate people from their workplaces, schools, and recreational spaces. This favors private transport, resulting in higher CO2 emissions per person.
Fragmentation, complexity, rising infrastructure costs, and irregular layouts create discontinuous and disconnected urban spaces, exacerbating socioeconomic disparities.
Recognizing the close connection between urban configurations, sustainability, and population health has highlighted that many European cities suffer from poor environmental health, contributing to increased premature death rates.
About the study
The researchers examined 919 cities covering 31 countries to classify them into various urban configurations. The aim was to explore how these relate to environmental exposures, CO2 emissions, and health.
The urban configurations were identified based on the local climate zones (LCZs) reported in previous research. Their use permits the comparison of cities based on their characteristics, assessed by a common standard.
European cities were classified into one of four types of urban configuration. These were:
- Compact high density cities (“compact”) which were small, had high population density, and little natural area left.
- Green low density cities (“green”) were large, had low population density, and had abundant access to natural areas and cycleways.
- Open low-rise medium and low density cities (“open medium” and “open low”, respectively) differed in size and in population density, but were either small or medium. Natural areas were at low or moderate accessibility levels.
These were assessed for motorized traffic flows, surface urban heat islands (SUHI) to evaluate UHI intensities, and air pollution (measured by tropospheric NO2 and CO2 emission per person).
What did the study find?
Most European cities (261 out of 909) were classified as "open low." The "open medium" (245) and "compact" (246) types were almost equal in number. The "green" type was the least common, with only 167 cities. Interestingly, Mediterranean cities had the highest proportion of "compact" cities.
City Centers vs. Outskirts
In most cities, built Local Climate Zones (LCZ) were prevalent in city centers, while natural LCZ were more common towards the outskirts. Motorized road density was slightly higher in the suburbs, but other road types were denser in city centers and gradually decreased towards the periphery.
Traffic volume, Surface Urban Heat Island (SUHI) intensity, and tropospheric NO2 levels were highest in the center. In contrast, CO2 emissions increased towards the city outskirts.
Associations with sustainability measures
Compared to the other types, higher flows of motorized traffic were associated with “compact” and “open medium” cities in all LCZs and all concentric regions.
However, these two types were similar in their traffic volumes. These also showed higher levels of NO2 exposure.
Most of the total urban population was packed into “compact” or “open medium” cities.
“Compact” cities demonstrated the lowest CO2 footprint, with amenities within easy reach, better traffic management and opportunities for by walking or cycling on dedicated networks.
The CO2 emission per capita was also much lower, however, in “compact” cities than in “green” cities. With urban sprawl comes increased complexity, irregularity, and fragmentation, reducing connectivity and continuity of spaces.
“Green” cities had much SUHI intensity than any other type. Yet, “compact” cities had lower SUHI intensity than “open medium” or “open low” cities. Of the latter, the “open low” cities had lower SUHI than the other outside the city centers.
The mortality rate in “green” cities was the lowest compared to all other types, with better environmental health.
Conclusions
The study indicates a clash between sustainability and health. The compact city configuration is in theory, the optimal, healthiest, and most sustainable city model. Yet compact cities have challengingly poor environmental quality and fail by health standards.
High density is associated with intensely polluted areas and fewer natural spaces. Motorized transport predominates, belying the theoretical advantages of walkways, cycleways, and proximity to amenities.
Small, low-density cities are probably better as they are. In contrast, compact cities may be made healthier via improved long-distance transport, more low-traffic and green public spaces, including sky gardens, street trees, and small gardens wherever possible, including the premises of houses, factories, schools, colleges, and institutions. However, this may raise property costs and exacerbate disparities.
This makes it “crucial for urban planners to monitor the environmental quality, accessibility, and equitable distribution of these spaces to promote environmental and climate justice.”
For large sprawling or rapidly growing cities, “measures such as densification, the provision of services, and an adequate mix of [residential and non-residential] buildings can help in creating more dense and diverse neighbourhoods with cultural, social, and employment opportunities.”
“Present day European compact cities [are] in a transition state that combines positive features, such as access to services and reduced carbon emissions, with challenges such as high traffic volumes and a poor environmental quality. Cities are complex systems and solutions require a holistic approach.”
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