Effects of Urbanization on Vegetation Degradation in the Yangtze River Delta of China: Assessment Based on SPOT-VGT NDVI

Abstract

Rapid urbanization has generated great pressure on natural resources. This research paper illustrates the utility of linking socioeconomic and remotely sensed imagery in order to investigate the interaction between ecological and socioeconomic processes within the context of urban growth. The approach focuses on the vegetation degradation index (VDI) developed from time series SPOT-VGT NDVI, the normalized difference vegetation index based on vegetation data provided by the vegetation sensor onboard the SPOT satellites. The VDI value of each square kilometer pixel has been calculated to depict spatial pattern of vegetation degradation, which are then aggregated into the city level. In terms of urbanization, 13 factors have been chosen and valued from statistics books and vector digital maps. With the sample set of 50 cities in the Yangtze River Delta region of China, spearman correlation analysis and multiple regression analysis have been adopted to investigate the causal relationships between urbanization and vegetation degradation. The findings are as follows: First, three hot-spot areas in vegetation degradation have been identified, which are spatially correlated with urban land expansion. The composite index of VDI has been manifested as an effective tool for assessing vegetation degradation. Second, economic and demographic variables, rather than the urban land expansion variables, have been verified to be the determinant factors for vegetation degradation. The rise of GDP growth rate, population growth or GDP per capita has significantly deepened regional vegetation degradation. Third and finally, the distinctively local findings that incomplete urbanization and idling cropland have probably increased vegetation degradation rates are worth noting. Although further studies are required for probing into detailed mechanisms and universality, the specific findings may provide a reference to similar studies, and should be quite useful for policy makers.