In Paris, patches of forest are replacing concrete to combat the heatwave

The orange heatwave alert is extended on Thursday to 17 departments, including Paris, Météo-France warned, with peaks of 38-39°C forecast, unprecedented for the end of May.

"I live right here and frankly I think it's so great to be able to sit down, walk around with my dog," Sixtine (who does not wish to give her last name), a 23-year-old marketing student, told AFP on Wednesday late afternoon in these 1.760 m2 of greenery complete with pétanque courts, which have replaced a roundabout in northern Paris since March.

"I really like coming here, you can really feel that it's cooler, it avoids the heat in the streets," she adds.

Beyond the "aesthetics", the fourth urban forest created by the City provides "a refuge during the strong heat waves for Parisians, tourists passing through, the most vulnerable, the homeless"... because the 79 trees planted lower the temperature by about 4 degrees, says Aminata Niakaté, deputy mayor in charge of the greening of public space.

"This is due to three effects: the shade of the trees creates coolness, the trees capture water from the soil and release it into the air like a natural vaporizer, this is evapotranspiration, and the de-paved soil captures and releases less heat," she explains.

Paris is among the European cities where the risk of excess mortality related to heat is highest: when the temperature is above normal, mortality is multiplied by 1,6 in those over 85 years old, according to a study published in The Lancet in 2023.

However, during "the great heat wave of 2003, the observation that triggered the feeling of urgency to act against global warming was that at the end of the night in Paris it was 8 degrees warmer than in the outer suburbs," emphasizes Renaud Paque, head of the mission to green Parisian public space "100 hectares".

"Improvement of physical and mental health"

Within the capital, the most vegetated districts have a lower risk of death during heat waves, a study published in January by Inserm, the Barcelona Institute for Global Health and the London School of Hygiene & Tropical Medicine showed.

Beyond the cooling effect of vegetation, "the reduction of pollution and the improvement of physical and mental health could play a decisive role," explained Hicham Achebak (Inserm), first author of the study, "although the exact mechanisms still need to be explored."

For researchers, "strengthening the place of nature in urban areas" is "a major lever to protect the health of Parisians in the face of global warming," summarized Mr. Achebak.

Elected in March, the Socialist mayor Emmanuel Grégoire promised a "massive" greening of the city to protect the most vulnerable from heat waves.

Another achievement: Pailleron Street, which serves a middle school, a high school and sports facilities, has been landscaped and partially pedestrianized: it is one of the 300 "children's streets" in the capital - which are to be increased to 1.000.

"Children are having fun, teenagers are cycling or meeting up, they have benches to sit on, fountains to drink from: all of this creates a collective life," Mr. Paque points out.

The municipality is already preparing the population for a heatwave scenario of unprecedented intensity: at the end of 2023, it organised "Paris at 50 degrees", a full-scale exercise mobilising firefighters, civil security associations, network operators and residents, nursing home residents and children in two districts.

A nightmarish scenario that could become reality from 2050 onwards, according to a study published in September 2024 in the journal Climate Services.