La chaleur en ville : sujet prioritaire et enjeu sanitaire en Méditerranée
By 2050, it is estimated that heatwaves will double, and by 2100, temperature increases in France could reach +4°C. Heat has therefore become a priority issue and a public health challenge in Mediterranean cities. This is referred to as “survival” urban planning.
Urban heat, a complex and cross-cutting issue
The issue of urban heat lies at the intersection of multiple scales, projects, professions, and complex actor systems. To translate data into concrete actions, a proactive and demonstrative policy is necessary.
In Cuers, a pilot city in the French department of Var, implementing a “low-temperature city,” numerous initiatives have been introduced: shade structures with sails on the main shopping street, light-colored paving for sidewalks, de-paving around tree trunks, and the planting of over 70 trees. Results by the summer of 2024: a temperature reduction of -35°C on the ground under the shade structures compared to the ground exposed to full sunlight, -15°C for the light-colored pavings, a greater sense of freshness in the city, and recognition of the landscape quality of its plant heritage.
To support French local authorities, ADEME has introduced the decision-support tool “Cooler My City.” Very user-friendly, this tool allows for quick calculations of the costs and benefits of implementing an initiative.
Individuals at the heart of the systems
The issue of urban heat is closely linked to the overall health of the population. According to researcher Franck Taillandier from the INRAE institute, the goal is to create communities that address the question of use and confront collective imaginations: What are the desires of local populations? What are their needs? Their fears?
This expert refers to the results of their socio-economic analysis, which demonstrate inequalities related to heat. Just as with access to green spaces, there is a socio-economic difference between high-income and low-income groups in terms of access to cooling areas. Heat thus emerges as a social issue.
The challenges of heat are also tied to the general perceptions of users in public spaces. Environmental psychology research provides insight into the various criteria that contribute to well-being, such as safety, noise, etc.
Pilot projects driving adaptation to climate change.
School courtyards are considered exemplary projects. Acting as micro-societies, the uses within schoolyards can sometimes be conflictual. By integrating the needs of children, the concerns of parents and teachers (particularly regarding the use of wood chips and potential accidents), schoolyards can become spaces of cooperation and play, showcasing the potential of a fairer society. In 2024, the CAUE supported 15 projects for the de-paving of school courtyards, and the Department is interested in expanding this initiative to all 71 middle schools in the Var region.
The Cool Noons project, led by AVITeM, aims to improve thermal comfort in our cities during the hottest hours. To achieve this, nine partners are working over 33 months to refine our urban spaces and uses to promote freshness. This pilot project is being implemented in five Mediterranean cities: Marseille, Lisbon, Imola, Budva, and Dubrovnik, all of which are tourist cities facing extreme heat in the summer. Various measures are being explored: nature-based solutions for public space renaturation such as ecological corridors, shading design solutions like sails or canopies, water-based solutions like fountains and maps of drinking water points in the city, and the enhancement of built heritage with air-conditioned interiors… A project to follow!
The holistic ecosystem of the city within nature
A paradigm shift is necessary to address the issue of urban heat: the human/urban being is part of Nature.
Architect Julio Jiménez, originally from Costa Rica, recalls the underlying paradigm that governs territorial thinking in the West: humanity sees itself as the master and possessor of Nature. He proposes moving away from an entirely engineering-driven approach and initiating a cultural change.
Inspired by the work of Alberto Magnaghi, he emphasizes the need to design local projects based on bio-geoclimatic materials, in symbiosis with nature and seasonality. According to him, simple, low-cost, and easy-to-implement solutions can be designed if they are inspired by Nature.
Regenerating our degraded urban ecosystems to address heat in cities
Three components are essential to urban ecosystems, according to Agnès Hannequin from the Regional Agency for Biodiversity: soil, water, and plants.
The soil, in its capacity (or inability) to retain rainwater, to be a living and healthy soil. Water must return to its natural cycle with infiltration at the onset, slowing its flow, and managing rainwater in the open air.
Plants must also be considered in an ecosystemic manner, meaning as a layer of healthy vegetation within ecological corridors.