99% of the population reside in the high human impact and countryside areas, and these are the areas where people have their daily living space. We are left with the view that the natural environments here have been maintained within the scope of human activities. Here below, we take as examples mixed forest in the country-side and mountains, and grasslands in the Aso District and elsewhere, and examine what happens when the relationship to human activities is cut off, and declines and changes begin to occur.
(1) Mixed forests
The “kunugi” (Quercus cicutissima) and “konara” (Quercus serrata) trees that make up mixed forests are called secondary forests, and arise several stages of vegetation phases after the climax forests such as the buna (Fagus crenata) and laurel forests are cut down and des-troyed. Figure 3-2-4 shows an example of phase patterns for areas from the Kanto Region westward. According to the figure, after the climax forests are cut down, the first things that invade the post-cutting zone are the seeds of herbaceous plants distributed over a wide range. Later, the herbaceous plants that mature in one or two years give way to herbaceous plants with multi-year maturations, and as sun tree forests such as “konara” and “akamatsu” (red pine) trees mature, the multi -year herbaceous plants begin to lose access to sunlight and the next vegetation phase arrives. Further, as the sun tree forests progress to full maturity, sasa grass and other undergrowth flourish on the floor of the forest, and the density of standing trees rises until the tree canopy closes over. At this point, the sun tree seeds that fall to the forest floor can no longer germinate and grow, and the phase shifts toward the “shii” (Castanopsis cuspidata chinquapin), “kashi” (oak), and other shade trees (laurel forests) that can grow even in such shaded conditions. So if the natural condition is left to itself, denuded land will eventually return to the climax forest beyond which it cannot advance.
Fig. 3-2-4 Lowland Vegetation Changes for Western Japan including Kanto Area
Source : Minoru Ishli, “Village Mountain Ecology” in “Protect the Nature of Village Mountains”
The mixed forests of countryside and mountain areas are caught in the sun tree forest stage and have been historically maintained by continued human intervention, and thus prevented from moving to the next vegetation phase. Mixed forests, also known as firewood and charcoal forests, have played important roles in farming and mountain villages because they have been supply sources for firewood and char-coal, and also for fertilizer. In the countryside and mountain areas, branches were cut off every three to five years and the cut branches were used as fuel. Moreover, standing “kunugi” and other trees were cut down in cycles of 15 to 30 years for use as firewood or charcoal. But because these cutting operations were conducted every year a little at a time, a natural regenerative production cycle was achieved. This harves-ting of a fixed amount of firewood and charcoal each year and the role of intervention played by the countryside and mountain areas prevented the vegetation from shifting to the climax forest, and the countryside and mountain maintained an equilibrium for long periods.
Moreover, the mixed forests of the countryside and mountain areas supported many life forms with which we are familiar. For example, the designated national butterfly, the “ohmurasaki” (giant purple butterfly), and the “gifucho” (Luehdorfia japonica) butterfly, as well as the horned beetle and the stag beetle, all make their habitats in the mixed forest. And cutting down the undergrowth leaves grass that serves as food sources for butterfly larvae, and promotes development of vegetation for adult insects, while the fallen leaves from the mixed forest creates a compost that horned beetle larvae find perfect for living in. We are left to observe that human activities in the countryside and mountain areas have helped to promote the flourishing of these life forms. Furthermore, on the bright forest floors of the countryside and mountain areas where human intervention reaches, we can often see in early spring such wildflowers as “tsutsuji” (Rhododendrum japonicum) and “katakuri” (Erythronium japonicum). So the countryside and moun-tain areas are not limited to production sites but have also come to play the dual role of “mountain playground” as well.
Among the “gifucho” butterflies, “katakuri” flowers, and many other insects and plants in the mixed forest, there are many species extant from the Ice Age that are now biologically rare. These species existence is said to have become possible only through the intervention of human activities in nature. In other words, according to one theory, the coexistent relationship between the mixed forest and man dates back to the slash-and-burn cultivation of the Middle Jomon Period. It is thought that in the course of these human activities of slash-and-burn cultivation and the later shaping of the countryside and mountain areas, the deciduous broad-leaf forests that were the natural vegetation of the Ice Age were able to maintain their existence up to the present by shifting to the laurel forests that are the natural vegetation of the modern mixed forests, and the “gifucho” butterflies and other life forms of that forest were thus able to remain in existence.
As can be seen, humans’ active intervention in the countryside and mountain areas helped to maintain a continuously coexistent rela-tionship between man and nature, including the life forms that lived there, and human activities had become incorporated into the circle of the ecological cycle of the countryside and mountain areas overall.
Beginning around 1955, however, the energy fuel source switched from firewood and charcoal to coal and then later to oil and natural gas, and agricultural fertilizer also switched from the compost supplied from the countryside and mountain forests to chemical fertilizers. As a result, the economic value of the countryside and mountain areas as a source of firewood or charcoal, or of fallen leaves, was suddenly lost, and agriculture became almost completely separated from the countryside and mountain forests. With the link between human activities and the forests cut off, the vegetation phases that had been blocked off restarted and the forests began changing into climax forests featuring densely luxuriant laurel forest. While this development could be viewed as being a change to the original vegetation, the countryside and mountain areas where people are no longer intervening can no longer support the continued existence of “gifucho” butterflies, “katakuri” flowers, and many other species having a deep relationship with human activities. A further problem is that countryside and mountain areas that have lost their economic validity become “unutilized land” and can forthwith only be recognized as land available for development, so becoming targets for development as soon as they return to natural vegetation. In other words, countryside and mountain areas located near urban areas are being opened up for shaping into residential or industrial land, while the mixed forests with their poor-quality lumber species are being steadily replaced by coniferous trees, and the extent of mixed forests is declining fast. It is in this framework that declines and improvements of nature in the high human impact and countryside areas are taking place.
(2) Grasslands in the Aso District
The vast scenic elements of “susuki” (tall goldenrod) and “shiba” (turf) that make up the grasslands of Aso were also nurtured as one part of the coexisting relationship between man and nature, and is a repre-sentative example of a secondary grassland in Japan (Figure 3-2-5). The volcanic regions of Aso, Kuju, and the Kirishima mountain range have been used since ancient times as a range land for cattle and horses, and the use of grassland for grazing cattle and horses, as well as for cutting grass to make dried hay for feed during the winter months has been maintained for hundreds of years and perhaps for more than a thousand years. The secondary grassland of “susuki” and “shiba” was created and maintained by rangeland burns, livestock grazing, and grass cutting, and without this artificial interference, the grassland would have returned back to its original natural vegetation of forests. The range burning carried out in mid-to late March is conducted to prevent the grassland from returning to forest and al so to improve its productivity for that year. It leaves the fire-resistant underground stalks of the range grasses, such as the “susuki” and “nezasa” (Pleioblastus variegatus), that cattle and horses like to eat, and eliminates fire-susceptible shrubs and harm-ful insects. Setting range fires require much manpower and experience to set up such things as fire breaks. In early April, livestock grazing commences, and the cattle and horses cooped up in pens all winter are released onto the grassland. Cutting of dried grass is conducted from mid-September to mid-October, and the cut hay is used as feed for the cattle and horses in the winter months. This cycle of human activities has maintained a vast grassland in the Aso District that has made possible the existence of such rare life forms as the grassland “orurishi-jimi” butterfly or such continental grassland-type plants as the “higotai”.
Lately, however, a number of changes due to conditions both in Japan and abroad, such as the introduction of evergreen foreign grasses that render range fires unnecessary has changed the grassland into a rangeland, personnel shortages due to depopulation and advancing age, and a depressed livestock industry due to deregulation of beef, has rendered the active intervention in and maintenance of nature through such methods as range burns uneconomical. As a result, maintaining the traditional grassland scenery has become difficult.
As can be seen from these examples of the mixed forest and grassland, in the cases where the natural mode originally maintained by economic necessity also served to bring the familiar blessings of nature to the local residents, the way to preserve this kind of natural environ-ment into modern times is to somehow incorporate the necessity of its existence into the economy and society, and not to look at it merely as “developable land.”