According to the National Survey on the Natural Environment conducted in 1990, forests cover ca. 246 200 kM or 66 per cent of Japanese land. In 1951, after World War II, the area of plantation was only 49 700 km. Considering the economic importance of the forestry production, Japan set up the forest policies to increase the plantation. Because of this effort, the total area of plantation becomes 103 300 km2. The major reason for sustaining this level of man-made forests is that most of these forests are less than 35 years old, and have not reached the standard harvesting age. Meanwhile, the forestry and wood industries in Japan faced difficult conditions; i.e., stagnation of timber prices, difficulties in maintaining labor force and competition with imported timber and wooden products.
Under these economic and social conditions, the activities of management, maintenance and improvement of forests are gradually going down. Approximately 50 per cent of natural forests are concentrated in Hokkaido. In other regions, only small and fragmented natural forests remain. A big evergreen broad-leafed forest, in particular, is rarely found. Groves owned by shrines and temples have excluded the disturbance caused by human activities and the secondary forests near residences have been preserved to a certain extent by human intervention. Although the ecological function of these groves is not comparable with that of huge forests, they have also contributed to the distinctive features of biological diversity. However, because of the decreasing activities of management and maintenance of these forests, shrubs and herbaceous species have invaded abandoned forested areas in Japan. Furthermore, since many groves are situated in urban districts, these groves have suffered from atmospheric pollution and diseases.
