A dense Miyawaki-type forest has just been planted between the A36 and the Doller promenade in Mulhouse. The goal: to restore biodiversity, capture as much CO2 as possible and create a vast island of freshness without humans interfering.
The hottest last twenty years of the Modern Era have been in the last twenty-two years, and the trend is expected to continue. The phenomenon particularly affects cities which, over the past decades, have swapped trees for bitumen, ultimately creating large heat islands. As a result, it is not uncommon to record much higher temperatures in urban areas than in the countryside.
This is why more and more cities are turning to trees. This is particularly the case with Mulhouse. The municipality has indeed launched with the objective of planting thirty-four hectares within five years.
With this in mind, a major project started a few months ago on the Promenade de la Doller, north of the city. The idea? Plant a Miyawaki type forest at least 24,000 plants. Several local companies, managed by the prime contractor company Trees-Everywhere, took part in the project. Cost of the operation: 200,000 euros, financed by the municipality and around fifteen local corporate sponsors.
What is a “Miyawaki” forest?
The technique, developed by Japanese botanist Akira Miyawaki of Yokohama National University, aims to support natural reforestation of a defined area. The first step is to select a variety of native plants (specific to the region). The seeds are then planted and germinated in nurseries. The plants, around the age of one or two, are then replanted on the chosen land – which will have been fertilized upstream.
It is then a question of planting several dozen different species (including bushes, medium-sized trees and large trees) in a very dense (up to three trees per square meter). Once erected, these forests are completely independent. There are about 3,000 of this type worldwide.
This “Miyawaki” method has already proved its worth, making it possible to maximize biodiversity and the power of carbon capture of the affected areas. The vegetation is also better rooted and more resistant extreme weather conditions, as well as possible illnesses. Regarding Mulhouse site, it will also be a question of creating an enormous island of freshness.
Ultimately, this “Miyawaki” forest should cover more than 8,000 square meters in a long strip of 500 meters around the highway (between ten and thirty meters thick, with a tree every 50 centimeters approximately). Depending on the species chosen, some trees will be able to climb up to about fifteen meters, allowing the passage to create an anti-noise barrier.