Changes in Fishery Resources in Relation to Water Environments in Osaka Bay

March 15, 2015An attempt was made to analyze the relationship between the change in the quantity of fishery resources and the change of phosphorus load deposited into Osaka Bay. The phosphorus load had steadily increased from 1955 to 1975, then decreased slowly towards the 2000s. The major benthic fishery organisms, such as octopus, shrimp and crab, mantis shrimp, tongue-fish and right-eye flounder, were employed to examine the characteristics of change in fishery resources in relation to water environments of Osaka Bay. Excluding shrimp and crab, catch amounts showed a largely equivalent response to phosphorus load in the bay. The results presented here demonstrate that a close relationship exists between phosphorus emissions and benthic fishery resources in Osaka Bay

A comparative method for evaluating ecosystem services from the viewpoint of public works

Nature-based solutions (NbS), such as the implementation of environmental conservation and restoration as public works projects, require accurate and cost-effective assessments of the values related to the projects. The values should represent collective ecosystem services, individual services such as food provision and water purification, and other intangible services. To comprehensively assess such services, we proposed a novel method, which we call the comparative evaluation method. Our method is able to assess the value of each service category of an NbS project from a single questionnaire survey. Survey participants are asked to compare values of multiple services having anchoring prices. Our method determines the permissible economic value of environmental public works (PEP) in response to the quantity of service. The questionnaire results used for analysis are limited to those from respondents who made their PEP evaluation on the basis of their consideration of the appropriate expenditure of taxes. In addition, the method controls for the effect of the satisfaction that a person experiences from doing good deeds to reduce an overestimation of the values of services. Moreover, PEPs are not influenced by the respondent's annual income, age, sex, or educational background, and are based on personal values. Applying this new method, we surveyed residents of the watersheds of Tokyo Bay and Osaka Bay and evaluated nine ecosystem services. Overall, our new method is shown to be an effective method for evaluating the ecosystem services of NbS projects from the viewpoint of public works

Green port structures and their ecosystem services in highly urbanized Japanese bays

Green port structures (i.e. green infrastructure in ports and harbors) featuring habitats for marine organisms have been promoted in Japan as part of a comprehensive policy to reduce the environmental impact of ports and carry out habitat conservation, restoration, and creation. In this study, we evaluated the ecosystem services provided by green port structures in two highly urbanized bays (Tokyo Bay and Osaka Bay) in Japan. Our results show that the provision of some ecosystem services can be limited by circumstances particular to ports and other areas with restricted access. In the case of green port structures that have strong usage restrictions, for example, cultural services can only be provided if relevant authorities are prepared to conduct public events while ensuring participant safety. On the other hand, green port structures with weak usage restrictions are often equipped with incidental facilities such as parking lots and restrooms; these facilities can enhance the provision of cultural services (e.g. recreation and environmental education). Green port structures in highly urbanized bays often have usage restrictions, but their proximity to large populations means that they can potentially provide numerous ecosystem services. However, our study shows that appropriate management goals, such as protecting species and ensuring healthy habitats, are needed to maintain the value of these services in highly urbanized and eutrophic bays