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From quantity to quality: enhanced understanding of the changes in urban greenspace

Wang, Jing, Zhou, Weiqi, Wang, Jia, Qian, Yuguo
Landscape ecology 2019 v.34 no.5 pp. 1145-1160
Landsat, cities, data collection, ecosystem services, green infrastructure, normalized difference vegetation index, planning, urban areas, vegetation cover
CONTEXT: Accurately quantifying changes in urban greenspace (UG) is the prerequisite for understanding ecosystem service. In addition to quantifying the “real” change of UG, it’s crucial to evaluate the change in quality of UG that is associated with quantitative change in area. OBJECTIVES: (1) Present a new index, dynamic index of UG (UGDI) that measures changes of UG by quantifying the loss and gain on UG simultaneously in a 100 m × 100 m grid cell. (2) Examine changes in the quality of UG measured by the NDVI. METHODS: We focused on nine Chinese major cities, and used 2.5 m resolution ALOS and SPOT image data collected in 2005 and 2010, respectively, and 30 m Landsat TM data. RESULTS: (1) By simultaneously quantifying the loss and gain, UGDI 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 low vegetation cover tended to increase in percent cover, and had larger magnitudes of UGDI. 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 that adding the same amount of new greenspace might not compensate the loss of greenspace due to the difference in quality. CONCLUSIONS: Results can enhance our understanding on dynamics of urban greenspace, and provide insights for UG planning and management to improve urban environment and sustainability.