Referring to potential natural vegetation (PNV) (a concept he studied in Germany), he developed, tested and refined a method of ecological engineering today known as the "Miyawaki method" to restore native forests from seeds of native trees on very degraded soils which were deforested and without humus. Using ecological theories and the results of his experiments, he quickly and successfully restored, sometimes over large areas, protective forests (disaster-prevention, environment-conservation and water-source-protection forests) at over 1,300 sites in Japan and various tropical countries, in particular in Pacific area[6] in the form of shelterbelts, woodlands and woodlots, including urban, port and industrial areas.