Climate change

Planting trees to save lives: combating urban heat islands

10 of March of 2023

The past century has seen global average temperatures rise by 1ºF. The struggle to combat climate change and reduce our environmental footprint has become a part of the daily discourse in the press and has instigated sustainability strategies from corporate and government bodies alike. 

We are all aware of the threat that climate change poses on the future of the planet and on the quality and quantity of our natural resources, but do we also realize the impact it has on our health

What is an urban heat island?

Although some people might overlook a rise of 1ºF in global temperatures, underestimating the gravity of the situation, the resulting consequences are more relevant that what meets the naked eye. Exposure to heat is associated with premature mortality, cardiorespiratory diseases, and increased hospital admissions. In summer, it worsens, especially when heat waves hit, and more dramatically in urban settings.

Cities are significantly more vulnerable to higher temperatures for a combination of determining factors: less vegetation, a higher population density, and impermeable surfaces that lead to a notable temperature difference between the city and its surroundings. Under these circumstances, we encounter an urban heat island and its (partially preventable) effects. 

Over 4% of summer mortality in European cities is attributable to urban heat islands, according to a study conducted by the Institute for Global Health in Barcelona published in January 2023. Nonetheless, there is something we can do about it: planting more trees

The results of the study, obtained with data from 93 European cities, highlight the substantial benefits of planting more trees in urban settings to attenuate the impact of climate change and of urban heat islands. The main takeaway is this: one third of heat-related urban deaths could be prevented by increasing the tree coverage in every city to 30%.

How to reduce the urban heat island effects?

The mechanism is very straightforward. Trees and vegetation lower surface and air temperatures because they provide shade and evapotranspiration. The subsequent lower temperatures reduce urban heat islands, thereby decreasing heat-related, preventable deaths (and lessening the burden to our health services). 

Because planting more trees can be challenging in many cities due to their design, urban reforestation can and should be combined with other interventions, such as green roofs and vertical gardens, an ancient technique used today that we featured in a previous post. We also need to preserve the trees we already have, since they take a significant time to grow, and re-distribute them to guarantee there is cover for our citizens regardless of the area of the city they find themselves.  

Many metropolises are starting to implement these changes. In the land down under, the city of Melbourne has led the transformation to manage the significant challenges of climate change, population growth and urban heating that are putting pressure on its buildings, services, and people. Through the Urban Forest Strategy, Melbourne aims to boost tree cover from 22% in 2020 to40% in 2040, planting over 3,000 trees annually to achieve this goal.

View of Melbourne and the Urban Forest Strategy

View of Melbourne and the Urban Forest Strategy. Anton Malishev (Architecture AU

Benefits of urban vegetation

Besides the by-now evident, life-saving benefits of planting trees and increasing vegetation in all its forms within urban environments, there are many more advantages that further justify this call for action. Vegetation reduces energy use by providing shade to buildings and decreasing the need for air conditioning. It also improves water quality by absorbing and filtering rainwater. Trees ameliorate air quality, lowering greenhouse gas emissions and removing air pollutants. Overall, trees and vegetation increase quality of life, provide aesthetic value, and from what we have learned from this study, even lengthen life expectancy.

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