How micro-forests are cooling French cities and boosting biodiversity

French cities are increasingly turning to “micro-forests” to cool urban areas and
boost biodiversity as municipalities prepare for another hot year in 2026.

The Miyawaki-style plantings feature dense clusters of native trees designed to grow quickly into self-sustaining green spaces. Projects are underway or planned in cities including Paris, Lille, Draguignan and Saint-Priest near Lyon.

In Saint-Priest, a 450m² micro-forest is being planted in Berliet Park as part of the commune’s greening strategy. Le Progrès reports it will be the town’s third such installation.

Officials say the aim is to create a “cool island” in a densely built-up neighbourhood lacking green space, alongside initiatives including a community garden.

Supporters of the Miyawaki method, developed by Japanese botanist Akira Miyawaki, say it can reduce temperatures during heatwaves, improve air quality and provide
habitat for birds and insects.

Paris has expanded greening projects around major public spaces, including near the Hôtel de Ville, while researchers in Lille are studying the environmental impact of similar miniature forests.

Among organisations promoting the approach is non-profit Boomforest, involved in projects since 2018.

Guillaume Dozier, Boomforest’s Miyawaki micro-forest project leader, said the aim is not only to create green spaces but also involve residents in planting.

“We hope to show that everyone has the power to act at their own level, sometimes through something as simple as planting a tree,” he said.

Mr Dozier said micro-forests should be viewed as one climate-adaptation tool rather than a standalone solution.

“The issues of biodiversity and urban heat islands are complex and no single model can solve them on its own,” he said.

He added that benefits such as cooling and habitat creation take time to develop as trees mature.

According to Boomforest, dense planting of native species can support biodiversity by creating habitats for insects and birds while contributing to ecological corridors across cities. It says micro-forests can also cool surrounding areas through shade and evapotranspiration.

However, the model’s expansion is not without debate.

France’s environmental agency ADEME says urban cooling remains a relatively new field of research.

In its Rafraîchir les villes guidance, ADEME notes that while nature-based solutions show promise, their effectiveness varies significantly depending on climate, location
and design.

Scientists have also cautioned against treating such projects as fully functioning ecosystems too quickly.

In a 2021 study, INRAE researcher Bastien Castagneyrol said that although early growth in Miyawaki plantations can appear impressive, long-term ecological performance in European conditions remains uncertain.

He warned that “tree diversity effects on ecosystem functioning are complex and context-dependent” and cannot automatically be assumed to work
the same way everywhere based on short-term results.