Urban green spaces can save more lives if placed right

In July 2021, mayors of 31 cities belonging to the C40 Cities Climate Leadership Group committed to increasing green (e.g. parks and trees) and blue (e.g. rivers and lakes) spaces to tackle the climate crisis. Signatories of the C40 Urban Nature Accelerator committed to two crucial goals for 2030 — quality total cover, specifically for the green or permeable spaces to occupy 30-40% of the total built-up city area, and equitable spatial distribution which includes blue or green space access for 70% of the population.

Four years since the declaration, at about the halfway mark to the 2030 deadline, a research paper published in the Lancet Planet Health journal has assessed the health impacts of the progress towards the Urban Nature Accelerator targets in C40 cities.

“Many cities are aiming to increase green spaces to improve climate resiliency and population health,” Greta K. Martin, one of the paper’s authors and a postdoctoral associate at the Department of Environmental and Occupational Health, Milken Institute School of Public Health, Washington, said. “Urban green spaces help improve health by creating spaces to exercise and gather with friends and family, reducing air, heat, and noise pollution, and reducing stress and anxiety.”

While prior health impact assessments have reported the associated health benefits of hypothetical increases in green spaces, their research “estimated annual avoided deaths across the 96 C40 member cities in terms of their incremental progress towards Urban Nature Accelerator targets,” Martin said.

Where you add green spaces matter

The study assessed 96 C40 cities, spread across 48 countries and six continents, and home to 291 million residents. Harnessing satellite data and global health databases, the researchers calculated annual avoided deaths based on increments in urban green cover under the Urban Nature Accelerator targets of quality total cover (QTC) and equitable spatial distribution (ESD).

The study modelled three different ways to add green spaces.

In the uniform scenario (even distribution of new green spaces), every one percent increase in green space (QTC) yielded an annual city median of 53 fewer premature deaths, and every one percent increase in population with nature nearby (ESD) yielded an annual city median of 15 fewer premature deaths.

In the nature-deprived scenario (distribution of new green spaces in low-nature areas), every one percent increase in green space (QTC) yielded an annual city median of 76 fewer premature deaths, and every one percent increase in population with nature nearby (ESD) yielded an annual city median of 27 fewer premature deaths.

In the population-centred scenario (distribution of new green spaces in densely populated areas), every one percent increase in green space (QTC) yielded an annual city median of 158 fewer premature deaths, and every one percent increase in population with nature nearby (ESD) yielded an annual city median of 50 fewer premature deaths.

“Adding green spaces near population centres or in areas with the least amount of existing nature could provide 2.7 and 1.4-1.7 times the health benefits of adding green spaces uniformly across cities,” Martin said.

Although less impactful than quality total cover improvements, the study shows that bettering equitable spatial distribution could significantly reduce premature deaths.

India’s cities “must safeguard existing green spaces”

Five C40 cities from India are part of the study – Bengaluru, Chennai, Delhi, Kolkata, and Mumbai.

“Across the five cities, increasing green area by 1% could reduce the number of annual premature deaths by 875-2,439, depending on where you add green spaces,” Martin said.

Increased urban green cover can move the needle for public health in India, according to Santonu Goswami, senior faculty at the School of Climate Change and Sustainability, Azim Premji University, Bengaluru. “The paper shows that increasing green spaces by just 1% could reduce premature mortality by at least 875 deaths, comparable to the annual death toll in Bengaluru due to road accidents. That is a big number!” Goswami, who is not a part of the study, said.

“Today, heat is the number one priority in Indian cities. Green cover can save lives as summers become intolerable,” Goswami noted.

However, South Asian cities tend to be densely populated, making it difficult to add more green spaces. It helps to think small-scale, suggests Martin. “While creating large parks in densely populated cities might be difficult, smaller scale green space improvements like lining streets with trees and adding small gardens can improve health while providing shade, controlling water run-off, and reducing heat,” she said. “Smaller parks at the block level should be mandatory across cities of all sizes,” Goswami added.

The immediate goals for urban planners and city councils should be to preserve existing spaces, Goswami said, “First, we must safeguard existing green spaces. Second, resurrect the blue spaces in our cities.”

Apart from long-term targets for green space expansion, Goswami proposes that India experiment with vertical and terrace gardening to help cool buildings and clamp down on energy spending.

“Adding green spaces is one piece of creating healthier cities. Clean air, walkability, and safety are all important to getting the most health benefits from urban green spaces,” Martin noted.

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Banner image: Lodhi Gardens in New Delhi. Adding green spaces near population centres or in areas with the least amount of existing nature could provide 2.7 and 1.4-1.7 times the health benefits of adding green spaces uniformly across cities. Image by Tanviechpilani via Wikimedia Commons (CC BY-SA 4.0).