Over 4% of deaths in European cities during the summer months are due to urban heat islands, and one-third of these deaths could be prevented if tree canopy cover reached 30%. These are the main findings of a study recently published in the journal The Lancet and conducted by the Barcelona Institute for Global Health (ISGlobal).
The study, which modeled data from 93 European cities, highlights the substantial benefits of planting more trees in cities to mitigate the impacts of climate change.
Exposure to excessive heat has been linked to premature mortality, the worsening of cardiorespiratory diseases, and increased hospital admissions. While this is particularly true during heatwaves, it also occurs with moderately high summer temperatures.
Cities are especially vulnerable because they have less vegetation, higher population densities, and impervious surfaces on buildings and roads that create a temperature difference between the city and surrounding areas—a phenomenon known as the urban heat island effect. According to the study, ongoing global warming is expected to worsen this effect in the coming decades.
“Projections based on current emissions reveal that heat-related illnesses and deaths will become a heavier burden for healthcare services in the coming decades,” says ISGlobal researcher Tamara Iungman, lead author of the study.
Preventable deaths
An international team led by Mark Nieuwenhuijsen, director of the Urban Planning, Environment and Health Initiative at ISGlobal, estimated mortality rates for residents over 20 years old in 93 European cities (totaling 57 million inhabitants) between June and August 2015. They then collected data on daily rural and urban temperatures for each city.
They estimated premature mortality by simulating a hypothetical scenario without urban heat islands. Next, they estimated the temperature reduction that would be achieved by increasing tree canopy cover to 30% and the associated mortality that could be prevented.
“Our goal is to inform decision-makers about the benefits of maintaining green areas in all neighborhoods to create more sustainable, resilient, and healthy urban environments,” explains Nieuwenhuijsen.
The results show that from June to August 2015, cities were on average 1.5ºC warmer than their surrounding rural areas. In total, 6,700 premature deaths could be attributed to warmer urban temperatures, representing 4.3% of total mortality during the summer months and 1.8% of year-round mortality. One-third of these deaths (2,644) could have been prevented by increasing tree canopy cover to 30%, thereby lowering temperatures.
Cities with the highest rates of heat-related excess mortality were located in the south and east of Europe, with these cities benefiting the most from an increase in tree cover. The authors acknowledge that planting more trees can be a challenge in some cities due to their urban layout. They also warn that tree planting should be combined with additional interventions, such as green roofs.
“Our results also show the need to preserve and maintain existing trees, as they are a valuable resource and growing new trees takes a long time. It is not just about increasing the number of trees in the city, but also about how they are distributed,” says Nieuwenhuijsen.
The analysis was conducted using 2015 data because complete population data was not available for later years. However, according to Iungman, the study provides valuable information to adapt urban environments and make them more resilient to the health impacts of climate change.
“Here, we only analyzed the cooling effect of trees, but greening cities has many other health benefits, including longer life expectancy, fewer mental health issues, and better cognitive functioning,” she adds.
“Understanding the benefits of policies such as increasing tree coverage can help inform actions to reduce risks and prevent avoidable deaths, especially with climate change,” says Antonio Gasparrini, Professor of Biostatistics and Epidemiology at the London School of Hygiene & Tropical Medicine (LSHTM) and one of the study's authors.
Via CicloVivo.
This article was written by ArchDaily Team. The translation is powered by AI.
