Living things play unique and important roles in material circulations in a rural area. Their abilities seem to get weak after land improvement.
This study consists of four examinations, using stable isotope ratio. The first one examined nitrogen transfer into living world by periphyton. The second one attempted to analysis the foodweb in Habahiro suiro canal. Detritus is principal producer like algae. The third one showed an area of distribution of stoney (Sterwpsyche sp.) and nitrogen restoration to terristrial area with the invertebrate. The last one made clear that nitrogen derived from farm house drainage was absorbed by Reed Canary grass (Phragmites australis).
These results suggested that not only preservation of continuity in aquatic area, but also various bottom materials and water velocity were essential measures to promote material circulations by living things.

View full abstract

This paper analyze residents' attitudes toward the mangrove vegetation, which affects a habitats for waterfowls in Lake Man, Okinawa, and toward the volunteer activities to conserve the environments in and around the lake. Lake Man, which is on the list of the Ramsar Convention with other twelve wetlands in Japan, is highly admired as a habitat of waterfowls. In recent years, the mangrove area there has been expanding too rapidly, and the wetland area has been decreasing. In the opinion of the experts, the expansion of the mangrove forest is undesirable to the conservation of the habitat of waterfowls, and the mangrove area should at least be kept at the present level. The purposes of this paper are to verify whether the attitude of the residents is consistent with that of the experts, and to analyze which kinds of residents' attributes including their place of residence make the difference of the attitudes. We use CHAID to segment residents' attributes statistically and to verify the characteristics of each group in the attitudes toward the conservation of Lake Man.
The main results of the CHAID analysis are as follows. (1) Although the experts suggest the rapid expansion of the mangrove area decrease habitat of waterfowls, more than half of the residents wish to maintain the mangrove area at the present level. (2) the residents in suburban agricultural area (Tomigusukushi) think more highly on the mangrove than urban area (Naha-shi), and then they are more inclined to wish the expansion of the mangrove swamp. (3) Those who set a lower valuation on the mangrove and appreciate the lake as a habitat of waterfowls are tend to have higher WTP for supporting the volunteer activities to clean Lake Man.
This paper show that the residents attitude toward the environmental conservation in Lake Man is not always consistent with the opinion of the experts. It is necessary to make a consensus among the residents by the enlightenment about the importance of the lake as a habitat of waterfowls and the present state of the mangrove swamp

View full abstract