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Tree Planting Mitigates Summer Heat Wave Mortality in Urban Areas


A recent study has highlighted the potential lifesaving impact of planting more trees in urban areas during the summer months. The study, which focused on European cities in 2015, revealed that out of the 6,700 premature deaths attributed to heat-related causes, approximately one-third (2,644) could have been prevented by increasing tree coverage in these urban regions by up to 30%.

Published in The Lancet, this modeling study also indicated that the presence of trees led to an average temperature reduction of 0.4 degrees Celsius during the summer season. Tamar Eungman, the lead author of the study from the Barcelona Institute for Global Health, emphasized the well-known link between higher urban temperatures and adverse health outcomes, including heart and respiratory problems, hospitalizations, and premature mortality. This study, the largest of its kind, specifically examined the connection between elevated temperatures in cities and premature deaths, shedding light on the number of lives that could be saved through enhanced tree cover.

The research highlighted a phenomenon known as "urban heat islands," where cities experience higher temperatures compared to their surrounding rural areas. The temperature differential is primarily a result of human activities such as deforestation, asphalt paving, and the use of heat-absorbing building materials.

With climate change set to exacerbate rising urban temperatures, there is an increased urgency for cities to adapt and improve public health. The study estimated death rates for individuals over 20 years old across 93 European cities during the summer of 2015, representing a total population of approximately 57 million people. Two modeling scenarios were analyzed: one comparing cities with and without urban heat islands and the other simulating the potential temperature reduction resulting from a 30% increase in tree cover.

The findings indicated an average temperature difference of 1.5 degrees Celsius between urban and rural areas during the summer of 2015. In all cities, 75% of the population lived in areas where the urban temperature was at least 1 degree higher than the surrounding countryside, with 20% experiencing a difference greater than 2 degrees.

While the study underscores the significant public health and environmental benefits of urban trees, the researchers acknowledged that increasing tree coverage should be complemented with other measures, such as altering ground surface materials to reduce nighttime temperatures, like replacing asphalt with trees. Currently, the average tree cover in European cities stands at 14.9%, making the goal of achieving 30% tree coverage a formidable challenge for many municipalities.

In addition to their role in mitigating the urban heat island effect, trees play a vital part in combatting climate change, improving air quality, and cooling the environment. They absorb pollutants, release oxygen, and provide shade, making them essential for creating healthier and more sustainable cities.