Accurate mapping of informal green space (IGS) features in an urban environment can provide a guideline for urban planners and policymakers to develop conservation efforts as well as increase recreational opportunities. In contrast with formal green space such as parks, informal urban green space has traditionally been difficult to track on a city-wide scale as this green space type includes largely spontaneous growth that can go unmanaged for years.
The study authors explored the distribution of informal green space in two large, densely-populated urban centers located respectively in Sapporo, Japan and Brisbane, Australia. The authors' specific goals were to assess the variance in land use, IGS characteristics, impact of distance from urban center on IGS distribution, and accuracy of land surveying in predicting the amount and variety of green space in a city. This process was carried out in both Sapporo and Brisbane through the development of a sampling site grid which included 121 survey sites situated in 50 m increments and centered on the urban core.
The study authors used a specific strategy to evaluate each factor included in the study goals. In order to evaluate land use, a custom geographic information system (GIS) layer was created and placed over aerial photographs of each city. This was coupled with qualitative assessments of land use types and associated feature characteristics. The type and amount of vegetation cover was measured visually and aided by the use of measuring tape. The authors also examined the relative accessibility of each survey site by identifying potential physical and psychological barriers to access such as fences or strongly worded signs like "keep out."
Results indicated similar levels of informal green space were present in both Sapporo (4.8%) and Brisbane (6.3%) with the Sapporo sample including a higher degree of feature diversity than in the Brisbane survey area. However Brisbane contained a much higher percentage of tree cover (27.8%) as compared with Sapporo (6.5%). Accessibility was high as over 80% of IGS in both cities was classified as either completely or partially accessible.
This study introduced a feasible and replicable strategy for assessing informal green space at a city level. A comprehensive review of unmanaged green space in a community may provide urban planners and policymakers with increased understanding of potential safety issues as well the areas' values for both conservation and recreation.
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