From quantity to quality: Enhanced understanding on the changes in urban greenspace

Authors: Jing Wang*, Research Center for Eco-Environmental Sciences, Chinese Academy Sciences, Weiqi Zhou, Research center for Eco-Environmental Sciences, Chinese Academy Sciences
Topics: Urban and Regional Planning, Land Use and Land Cover Change, Quantitative Methods
Keywords: Urban greenspace change, dynamic degree, turn-over, vegetation quality, urban ecology, China
Session Type: Paper
Day: 4/3/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Council Room, Omni, West
Presentation File: No File Uploaded

Accurately quantifying changes in urban greenspace (UG) is the prerequisite for understanding ecosystem service it provides. Previous studies have largely focused on the quantitative net change in percent cover, but not the quality in UG. Here we present a new index, dynamic index (DI) that measures changes of UG by quantifying the loss and gain on UG simultaneously. In addition to changes in quantity, we examined changes in the quality. We focused on nine major cities in China, and used 2.5 m resolution AlOS and SPOT image data collected in 2005 and 2010, respectively, and 30 m Landsat TM data. We found: 1) By simultaneously quantifying the loss and gain, DI can identify the areas with dramatic turn over on vegetation cover that otherwise would not be able to be revealed by net change, or gain and loss alone. 2) Areas with relatively low vegetation cover tended to increase in percent cover of UG, and had larger magnitudes of DI. In contrast, the area with high vegetation cover generally experienced reduction in percent cover. 3) The NDVI value of newly-created greenspace in all nine cities was lower than that of lost greenspace, suggesting increase in coverage may be compromised by decrease in quantity, however, does not necessarily mean increase in ecosystem services provision. The results highlight the importance to examine the quality of newly generated UG, in addition to quantity, and have important implications for UG planning and management, given the limited land resources for greening in cities.

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