Peter Yeung per Reasons to be cheerful si occupa di microforeste e presenta un metodo di riforestazione sviluppato da un botanico giapponese, Akira Miyawaki, negli anni Settanta.

Il concetto è quello di piantare specie arboree originarie della zona in modo molto denso e stratificato, tre per metro quadrato, al fine di ricreare le condizioni riccamente fertili delle foreste primitive naturali che un tempo coprivano il pianeta.

On the far eastern edge of Paris, along the outer rim of the infamously traffic-clogged périphérique ring road, a radical method for reforestation has begun to show green shoots of hope in the most unexpected circumstances. There’s a dense, green thicket of more than 30 species of trees and plants — willows, elms, oaks, limes, poplars and more — towering above what is an otherwise unloved, concrete-filled corner of the French capital. “Look at it, it’s like a jungle,” says Damien Saraceni, co-founder of Boomforest, the French nonprofit behind the project. “This has all grown in just a few years. It brings so many different benefits. And we don’t do anything to maintain it.”

Il metodo Miyawaki renderebbe possibile riforestare un’area in soli tre anni:

Developed by the Japanese botanist Akira Miyawaki in the 1970s, the concept is to plant tree species that are native to the area in a very dense and layered manner — three per square meter — in order to recreate the richly fertile conditions of the natural primitive forests that once covered the planet. It is in contrast to the slower, more orderly and homogeneous processes of traditional reforestation. Proponents claim that this method can produce a self-sufficient forest in just three years and that these forests grow faster, are denser and contain greater biodiversity than conventional forests. A Miyawaki forest in Japan, according to his own research, can grow one meter a year and can reach maturity in 15 to 20 years — 10 times faster than the average. What’s more, they can in theory be cultivated in all kinds of unconventional locations: roundabouts, factories, schoolyards, or indeed, ring roads.

Il metodo Miyawaki è però applicabile in tutti i climi?

Nonetheless, some research suggests that Miyawaki’s method may not be applicable in all climates. A study on the arid Mediterranean island of Sardinia in 2011 found that there was a tree mortality rate of between 61 and 84 percent after 12 years. However, more recent and robust experiments are showing better results for the method. Florent-Xavier Gadea, a researcher at Paul Sabatier University in the city of Toulouse, is running a 1000-square-meter project that began in March 2021. Of the 3,000 trees that were planted, about 16 percent had died 16 months later.

Intanto a Parigi è stato lanciato il progetto Boomforest dopo che i suoi fondatori hanno ottenuto finanziamenti nell’ambito del Bilancio Partecipativo:

In Paris, the Boomforest project launched after its founders won funding as part of the Participatory Budget, which allows residents to vote on spending for municipal projects. That allowed the nonprofit to create the first micro-forest – which contains 1,200 trees in a 400-square-meter space in the east of the city – in 2018. Since then, Boomforest’s rapid reforestation efforts have bloomed, and it now has about 20 projects in France, mostly at the initiative of local residents who have heard about their work. Paris City Hall said in 2020 it would plant 170,000 trees using the Miyawaki method – which it described as an “innovative planting method” – over the next six years.