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  • Writer's pictureArchie Milligan

The Miyawaki Method

Dr Akira Miyawaki passed away 16th July 2021, yet his flourishing legacy of thousands of forests across the globe, and the ubiquitous success of his methodology has inspired conservationists the world over.

Who was Dr Miyawaki

Dr Miyawaki was a Japanese botanist and an expert in plant ecology who specialised in seeds, natural forests and phytosociology (the study of how plant species interact with each other within communities).

He dedicated his life to restoring natural forests and degraded land, developing a signature method for growing naturally biodiverse forests that can rapidly outgrow and outlast typical monoculture forests.

As a student in the 1950s he learned about the nascent concept of potential natural vegetation (PNV) which complemented his studies of phytosociology. This knowledge directed his investigations of Japanese vegetation, prompting his exploration of Shinto sites and their sacred shrine forests (chinju no mori).

He noticed that these protected areas around shrines, cemeteries and temples contained highly biodiverse populations of native vegetation. These resilient ecosystems stood in stark contrast to the non-indegenous coniferous forests of larch and Japanese cedar that commanded much of the landscape.

The Shinto sites’ old indegenous forests consisted of four categories of native plants: main tree species, sub-species, shrubs, and ground-covering herbs. These four categories, along with his knowledge of PNV, phytosociology and his site surveys formed the constituent parts of Miyawaki’s methodology for planting forests.

The Method

Thus, his work developed into the Miyawaki method - the prioritsation of the natural development of forests using native species. This method first requires analysis of the site conditions and of local vegetation in order to determine the PNV.

The PNV dictates the various species for each layer of the forest, while the ratio of each species is based on a variety of factors, such as the site conditions and the composition of the soil.

This process, along with assessment of local indegenous vegetation and forest structures elsewhere in the world, allows us to choose which particular indigenous plant species to grow and how much of it.

The next step in preparing the site requires a soil survey to help select the type of mulch and soil nutrients required to improve the quality of the soil for plant growth.

Following this, we collect seeds from local trees to grow seedlings or obtain seedlings of local variants of tree species. There are specific recommendations for how to raise the seedlings, including growing them under shaded covers.

Once the species are selected and the site is prepared, we plant the chosen species using dense and mixed planting techniques to create multi-layered and biodiverse native forests.

The seedlings ought to be planted 20,000 to 30,000 per hectare, rather than the usual 1000 per hectare, along with stakes for support. This planting stage can be a participatory event for the local community, engaging associations, schools and locals in ecological work.

We apply a mulch made up of local materials to nourish and protect the seedlings, replicating the security offered by leaf litter in a natural forest.

Lastly, the Miyawaki forests should be maintained for the first 2 to 3 years, requiring regular water and deweeding. After this stage, they will become self-sustaining and less vulnerable.

The Benefits of Miyawaki Forests

There are myriad benefits from growing Miyawaki forests. Firstly, they are able to grow into mature ecosystems in 20 years, which is astounding when we compare this to the 200 years it can take for forests to regenerate on their own.

Further, Miyawaki forests can act as oases for biodiversity, supporting up to 20 times as many species as non-native, managed forests. A Dutch study observed that animal biodiversity of a Miyawaki forest is on average 18 times higher than that of a conventional forest. We can also observe from 2 to 162 times more of a given animal, depending on the species.

Importantly, pollinators such as butterflies and bees, beetles, snails and amphibians are some of the animals that thrive with greater diversity of food and shelter. These benefits are particularly stark in urban areas, where Miyawaki forests can serve as islands of biodiversity that offer protection from the dangers of urban environments.

These tiny urban forests have the potential to serve as wildlife corridors and biodiverse sanctuaries for animals, if enough of these forests can be grown in close proximity to one another.

Green spaces like urban forests also have positive effects on people’s health and well-being. They have been shown to reduce stress, anxiety, solitude, cardio-vascular and respiratory diseases.

Additionally, planting events, citizen science and community engagement with Miyawaki forests are excellent opportunities for social contact and cooperation within a community.

A Miywaki forest can also help reduce pollution by absorbing up to 15% of toxic particulate matter in the air through its trees’ leaves. The tree canopy also provides a boundary, inhibiting some pollution from crossing it.

As we feel the effects of global temperature rises, we are seeing more frequent dangerous heat events across the world, especially in cities. Miyawaki forests provide important temperature reduction effects.

Heat island phenomenon - where urbanised areas experience higher temperatures than outlying areas - can occur frequently in summer. Even small forests have a noticeable effect and are able to make the air cooler by up to -2 degrees celsius.

Not only this, but the air is also less dry and the vegetation provides much needed shade for people and animals.

Miyawaki forests are also capable of restoring soil stability. The diversified vegetation forms a matrix-pillar system with root entanglements that helps to restore degraded land and prevent any further erosion. Furthermore, these diversified forests can help reduce the risk of and damage of flooding.

These forests are also useful for reducing noise pollution. A Miyawaki forest will continue to improve its sound-proofing performance as it grows, reducing up to 10dB once it is fully formed.

It may serve as an inexpensive and aestheically pleasing alternative to conventional noise barriers that also have significant carbon footprints.

Miyawaki and the Climate

Miyawaki forests offer a host of benefits for our environment, to wildlife and to ourselves. These forests also have the potential for helping to address climate change, making them an appealing option for environmentalists.

Reforestation is a key part of strategies to limit the rise of global temperatures to 1.5 degrees celcius and there are some large scale initiatives like the Bonn Challenge, Trillion Trees Vision and the World Economic Forum’s project setting ambitious targets. It is estimated that new or restored forests could remove up to 10 gigatons of CO2 equivalent by 2050.

However, as we have already read in this article, not all forests are as effective as each in sequestering carbon. Mature forests of indigenous trees soak up much more CO2 than the monoculture plantations that unfortunately dominate many reforestation projects.

As our understanding of other factors that affect carbon sequestration improve, such as carbon in the soil, it is becoming evident that growing the correct kind of trees is equally as important as the number.

Integrating the Miyawaki method into large scale reforestation projects could have a significant impact in improving the effectiveness of carbon sequestration initiatives.

That being said, it is important to understand that Miyawaki forests ought not to be seen as an alternative to protecting the existing indigenous forests that we have left.

These small and separate green spaces cannot replace the extensive regions of forest that are vital to the survival of so many species. The Miyawaki method gives us a useful blueprint on how to effectively restore degraded land and reforest areas we’ve lost.

So, whether you’ve a degraded field, a patch of wasteland, or some unused space in your neighbourhood, a Miyawaki forest is an opportunity to give back to the environment, reconnect with nature, and connect with your local community.

By Archie Milligan ©


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