Evaluating ecosystem functions of open space (vacant space/ unused space) in urban area is an important task for enhancing the human well-being using it multifunctionally. The open space in Japanese urban or suburban areas is rapidly increasing along with the decrease of birthrate and increase of aging population and depopulation relating to them. Therefore, it is demanded to evaluate the functions and emphasize the value of the open spaces for sound urban planning.
In order to establish the standard scheme to incorporate the insight of ecosystem functions into urban planning, we evaluated biodiversity and some important ecosystem functions of open spaces of residential area in Shiroi City near Tokyo. In our study, the functions of mitigation of heat-island effect, watershed conservation function, and disaster prevention function were evaluated using GIS techniques. Cooling effect was valued by using each size of land and type of them (ex. grass land, wet grassland, embankment and abandoned farmland). Watershed conservation function was valued by using Digital Elevation Model and flow accumulation. Disaster prevention function was valued by using population data. Biodiversity of the open spaces was evaluated by a citizen participating field survey of distribution of some indicator species.
There were about 1,400 open spaces in Shiroi city. In Edo era, including this area, was used as pastureland for horses which Edo shogunate had used, and grassland had been maintained. The field survey revealed that several open spaces with grassland vegetation kept a high plant diversity including endangered species (Cynanchum paniculatum, Patrinia scabiosifolia) in national or local Red List. The ecosystem functioning was suggested to be high in such grasslands. Therefore, appropriate conservation planning of the open areas can be a green infrastructure plan to maximize the ecosystem services together with the biodiversity.
We are now making the green infrastructure map reflecting spatially explicit condition and potential of ecosystem function provision and biodiversity conservation. Furthermore, an environmental educational program to derive a novel services from the open spaces is planning by collaborating with a private childcare facility. The creation of maps and development of utilization programs will change the open spaces into multifunctional infrastructure, which will contribute to the improvement of the well-beings of residents.