Contemporary forests, created according to forestry principles, in his opinion, are neither the most suitable candidates to address climate change nor the most resilient vegetation for the geo-bioclimatic conditions of Japan.

With the results of his experiments, he restored protective forests in over 1,300 sites in Japan and various tropical countries, in particular in the Pacific region[8] in the form of shelterbelts, woodlands, and woodlots, including urban, port, and industrial areas.

Miyawaki demonstrated that rapid restoration of forest cover and soil was possible by using a selection of pioneer and secondary indigenous species that were densely planted and provided with mycorrhiza.

Miyawaki was primarily a botanist who specialized in plant ecology and seeds, who wrote a thesis on the subject in the Department of Biology at the University of Hiroshima.

[11] From 1980 to 1990, in cooperation with laboratories of phytoecology and universities, Miyawaki led botanical and phytosociological inventories to map vegetation throughout Japan, compiled into a ten-volume, 6,000-page study.

His proposals were not initially met with positive feedback, but in the early 1970s, Nippon Steel Corporation, which wanted to plant forests on embankments around its steelworks at Oita, became interested in his work after the death of previous conventional plantations and entrusted him with a first operation.

The method has been tested successfully in almost all of Japan, sometimes on difficult substrates, including plantations to mitigate the effects of tsunamis on the coast, or typhoons in the port of Yokohama, wastelands, artificial islands, fixing crumbling slopes after road construction, and creating a forest on a cliff freshly cut with dynamite to construct the Monju Nuclear Power Plant in Fukui Prefecture.

[1] His methodological work in the 1970s and 1980s on woodland management also formed the basis for the concept of "tiny forests", where small urban plots of land around the world can be densely planted with many different local species of trees to reintroduce varied wooded habitats that are rich in biodiversity.

[16] In 2018, the Miyawaki method was implemented by the boomforest.org team in Paris, France, to restore a 400-square meter area near Porte de Montreuil, in the Boulevard Périphérique, a controlled-access dual-carriageway ring road around the city.

[23][24] In the United Kingdom, Miyawaki's "tiny forest" method was adopted by the environmental charity Earthwatch Europe with the aim to develop a hundred urban projects nationwide by 2023.

[33][34] Other American Miyawaki forests have been planted in Griffith Park in Los Angeles and on Yakama Indian Reservation in Washington state.

[35] In January 2021, Masood Lohar, a former UNDP officer, created the Clifton Urban Forest in Karachi, a private initiative operating over 200 acres on a coastline landfill site and following Miyawaki's techniques.

[37] In August 2021, Imran Khan, Prime Minister of Pakistan, inaugurated the largest urban Miyawaki forest project in the world at Saggian.

In 1998, Miyawaki piloted a reforestation program dominated by Quercus mongolica along the Great Wall of China, and gathered 4,000 people to plant 400,000 trees, with the support of the Aeon Environment Foundation and the city of Beijing.

[citation needed] Miyawaki also contributed to the massive reforestation in China by its government and Chinese citizens in Pudong, Qingdao, Ningbo, and Ma'anshan.

One criticism is the high cost of the initial establishment of a Miyawaki forest (nursery, soil preparation, dense planting) - around 3000 Euros per 100m²,[16] with a reasonable pilot project being around 500m².