Satoyama, a traditional Japanese agricultural landscape, requires continuous human care because it is an artificially created natural environment and maintained by human-nature interactions. A small, endangered cyprinid fish, Pseudorasbora pumila, now only inhabits irrigation ponds in Satoyama scince their original flood plain habitat disappeared in Japan. Recent depopulation and aging in rural areas have caused deterioration and loss of Satoyama habitat. We investigated the value of a Satoyama area as P. pumila habitat by means of questionnaire and analyzed factors affecting inhabitants. awareness of importance of Satoyama landscape using the contingent evaluation method. We surveyed 549 households in the area and scored respondent surveys. More respondents was agreed with donation for habitat conservation than disagreed. Respondents showed greater recognition of keywords to be to relate to Satoyama landscape had more interest in conservation of P.pumila habitat. Our results suggest that the inhabitants in the study area evaluate Satoyama landscape for agricultural resources but also historical and environmental heritage. On the other hand, we estimated approximately 40％ of ponds at nearly 500 sites were already abandoned, suggesting that adverse conditions forced the caretakers to leave despite wanting to maintain the environment for the next generation. Mainstreaming biodiversity will play an increasingly important role in conservation of Satoyama and its ecosystem services.

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This paper describes structural and historical changes of floodplains, and reviews three key components of flood disturbance (inundation frequency, hydraulic forces, and deposition rate) in natural and regulated rivers to examine the use of flood-channel excavation as a floodplain recovery method in Japanese lowland rivers. Pristine floodplains once had broad backswamps, but land development and levee construction eradicated their natural configuration. Inter-levee floodplains changed from dynamic systems with active channels to static systems with dense riparian trees between 1975-2007 in the Kiso River. Flood-channel excavation increases inundation frequency to equal or greater levels than original floodplains. However, hydraulic forces and sedimentation also greatly increase with excavation and cause physical instability, making it difficult to autonomously maintain itself for a long period of time. Consequently, we suggest a cyclic flood-channel excavation as an approach to better managing inter-levee floodplains.

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We analyzed the monitored data in nine shallow eutrophic lakes in Japan to quantify the effect of retention time and nutrient concentration on the internal organic production. Using the regression equation obtained from the distribution of COD and chlorophyll-a concentrations, we have defined the external COD when chlorophyll a concentration at 0 μg L^-1. We also defined internal COD production (ΔCOD) as the difference between total and external COD concentrations. As a result, the relationship between retention time (day) and production of ΔCOD unit per phosphorus (ΔCOD/TP) is represented by the following equation. ΔCOD/TP=36.0 log (Retention time in days)-23.5 (R² = 0.78, p<0.001) Only Lake Kasumigaura (2006-2010) were out of this relation. The correlation coefficient between the residence time and the production of ΔCOD unit per nitrogen (ΔCOD/TN) was lower than that of TP. In shallow lakes, therefore, it was found that ΔCOD are affected by residence time and TP concentration.

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The factors causing water pollution in a basin with scarce water resources was studied in Kagawa Prefecture. The research was conducted in the Shin River basin, which is one of the main basins in Kagawa Prefecture, on October 23, 2010 during the non-irrigation season and on July 16, 2011 during the irrigation season. During the non-irrigation season when the quantity of river water decreased, the number of algal cells increased to 2.3×10⁴−7.8×10⁴ cells mL^-1 in accordance with the increase in the concentration in irrigation ponds, and species composition changed to Pseudanabaena sp. as well as irrigation pond. Although Microcystis sp. was also dominant in the middle/lower reaches as well as the irrigation ponds during the irrigation season when the quantity of river water was relatively abundant, cell numbers were lower than in October. In addition, the number of algal cells in the river correlated well with δ¹⁸O in the river water; irrigation pond phytoplankton is supplied to rivers when water flows from irrigation ponds to the river. The influence of irrigation ponds on rivers was found to increase during non-irrigation seasons when irrigation water is scarce and precipitation is low, and so the quantity of river water decreases.

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It is a persistent problem that academic research findings are often not applied to benefit society and social capital improvement does not occur ex-post assessment. To solve this problem, I propose the following approach: (1) number of government should be increased; (2) government should create a structure being evaluated by willing to attend scientific meetings and publish articles in academic journals; (3) academics should reach out to citizens and offer them the opportunity to learn the latest findings about the environment; (4) government should make it possible to request multiple-year research appropriation; and (5) government should institute ex-post assessment systems in order to create feedback mechanisms. Collaboration among citizens, government and the academy must be established, and adaptive management should be put into practice with the goal of creating a sustainable, abundant society for future generations.

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