Economy of Japan
The Japanese agricultural sector accounts for about 1.4% of the total country's GDP. Only 12% of Japan's land is suitable for cultivation. Due to this lack of arable land, a system of terraces is used to farm in small areas. This results in one of the world's highest levels of crop yields per unit area, with an overall agricultural self-sufficiency rate of about 50% on fewer than 56,000 km² (14 million acres) cultivated.
Akira Miyawaki
The more his research progressed, the more he found that the current forest vegetation of Japan (24.1 million hectares, or 3.5 billion cubic meters of timber on more than 64% of the country) had moved away from potential natural vegetation, due to the introduction of alien species by man. He noted that conifers (still considered in the 1970s as indigenous by many Japanese, including botanists), which became dominant in many forests, are actually an introduced species, and were only naturally present at high altitudes and in extreme environments (such as mountain ridges and steep slopes). They have for centuries been planted there to produce timber faster, and they acclimated. This led Miyawaki to think about forest other than as a source of greenery, recreation or timber. He became interested in the functions of allelopathy and complementarity of species in naturally wooded areas.