The difference in temperature in summer between an urban area (with less vegetation, more population and heating of the asphalt) and the surrounding areas is a phenomenon called urban heat island and 4% of summer mortality in cities is attributed to it European. A third of these heat deaths could be avoided by increasing trees in cities by 30%.
This is the main conclusion of a study on the urban heat island carried out in 93 European cities, including the Spanish Madrid, Barcelona, Valencia, Malaga, Palma de Mallorca, Bilbao and Alicante, led by the Institute for Global Health of Barcelona (ISGLobal) and published in the scientific journal “The Lancet”.
The results of the study underscore the significant benefits of planting more trees in cities to mitigate the impact of climate change.
Trees and their effect against heat in cities
From June to August 2015, cities were an average of 1.5 degrees warmer than their surrounding areas.
According to the study, 6,700 premature deaths can be attributed to rising urban temperatures, representing 4.3% of total mortality during the summer months and 1.8% of year-round mortality.
A third of these deaths (2,644) could have been avoided by increasing tree cover to 30% of urban space, thereby reducing temperatures.
In general, the cities with the highest excess heat mortality rates were in southern and eastern Europe, with these cities standing to benefit most from increased tree cover.
The study highlights the substantial benefits of planting more trees in cities, although the authors acknowledge that this may be difficult in some cities due to their design, and that planting trees must be combined with other interventions such as green roofs or other alternatives to reduce temperatures. .
The threat of climate change
Exposure to heat has been associated with premature mortality, cardiorespiratory diseases and hospital admissions and not only with heat waves, it also occurs with moderately high temperatures in summer, according to ISGlobal.
Cities are especially vulnerable to high temperatures due to less vegetation, higher population density and impervious surfaces of buildings and streets, including asphalt, which cause a temperature difference between the city and surrounding areas, the phenomenon called urban heat island.
“In view of global warming and urban growth, this effect is expected to worsen in the coming decades,” says this research institute promoted by the La Caixa Foundation.
“Predictions based on current emissions reveal that heat-related illnesses and deaths will become a major burden on our health services in the coming decades,” he says. Tamara Iungman, ISGlobal researcher and first author of the study.
/EFE/Luis ColmeneroAn international team led by Mark Nieuwenhuijsen, Director of ISGlobal’s Urban Planning, Environment and Health Initiativeestimated the mortality rates of people aged 20 years and over residing in 93 European cities (a total of 57 million inhabitants), between June and August 2015, and collected data on daily rural and urban temperatures for each city.
First, they estimated premature mortality by simulating a hypothetical scenario without an urban heat island.
Second, they estimated the reduction in temperatures that would be obtained by increasing tree cover to 30%, as well as the deaths that could be avoided.
“Our objective is to inform those responsible for local administrations of the advantages of integrating green areas in all neighborhoods to promote more sustainable, resilient and healthy urban environments”, explains Nieuwenhuijsen, in addition to preserving existing trees.
The analyzes were made with data from 2015 because population data was not available for later years, but, as Tamara Iungman points out, the results are generalizable and the study provides valuable information to adapt our cities and make them more resilient to the impact of climate change. .
“Here we only look at the effect of trees on temperature, but increasing green areas in cities has many other health benefits, including increased life expectancy, reduced mental health problems, and improvements in health. cognitive function of people”, he adds.