In Paris, greening reduces mortality during heat waves, according to a study

"The most vegetated districts present a lower risk of death during periods of intense heat," summarizes Inserm in a press release on this study, published at the end of January in the journal npj Urban Sustainability, carried out jointly with the Barcelona Institute for Global Health (ISGlobal) and the London School of Hygiene & Tropical Medicine.

Europe is increasingly affected by summer heatwaves, against a backdrop of global warming, with detrimental effects on health: more than 60.000 people died as a result of the heat in 2024.

The risks are particularly pronounced in large cities, especially because of the urban heat island effect, which slows down the cooling of many urban areas.

The beneficial effect of vegetation (parks, gardens, green roofs, etc.) in reducing mortality is already well documented: a study published in 2023 in The Lancet suggested that vegetation could reduce the number of heat-related deaths by a third.

But this new study sheds more light on the matter by precisely analyzing the differences within the same city, in this case Paris.

The French capital, in the midst of a municipal campaign a month before the elections, is a textbook case in more ways than one: due to its high population density, the significant presence of heat islands and marked social inequalities.

However, this last point can complicate the analysis: if there are fewer deaths in the greenest neighborhoods, is it thanks to the greenery, or because these areas are generally more socially advantaged?

More than the socioeconomic status of residents, it is primarily the age and characteristics of buildings (those built before the 1970s being less well insulated), as well as the presence of green spaces, which varies from 1,4% in the 2nd arrondissement to 20,4% in the 13th, that determine the risk of recording more deaths during periods of intense heat, the authors emphasize. They cross-referenced multiple data points on mortality and urban planning in Parisian neighborhoods.

"Contrary to popular belief, the wealthiest districts of Paris are, on average, more vulnerable to excess mortality linked to extreme heat," explains researcher Hicham Achebak, lead author of the study, quoted in the Inserm press release.

"This phenomenon can be explained by a low presence of green spaces, combined with dense and mineral old buildings in these neighborhoods," he argues.