Vegetation cover dynamics associated with rapid urbanization in metropolitan areas of East China (1998-2010)

Abstract

It has recently gained increasing attention to promote sustainable urbanization in China due to the environmental consequences associated with the rapid urbanization in the past two decades. How vegetation cover, as an important indicator for environmental sustainability, was affected by different urbanization trajectories in China’s major metropolitan areas is of great interest but rarely studied. In this paper, we used DMSP/OLS nighttime light time series images and SPOT-VGT satellite-derived Normalized Difference Vegetation Index (NDVI) to evaluate effects of urbanization on vegetation cover in the six major metropolitan areas (urban agglomerations) of East China over the last decade. We mapped urbanization dynamics at regional scales with nighttime light data and identified different urbanization trajectories based on the temporal signatures. The NDVI was then added to study the characteristics and change of vegetation cover in the areas with different urbanization trajectories. The study revealed that in general the vegetation cover decreased with an increase in level of urbanization. When compared to the average change rate of NDVI in the non-urban areas (which in fact showed an improvement trend in all six regions), the result indicated a negative average change in vegetation cover in all of the selected metropolitan areas. However, we should be aware that the trend was not merely a downward trend but was a U-shaped curve. In other words, the decrease rate accelerated at the early stage of urbanization and recovered in the later stage of urbanization, and the peak value appeared in different stages across different regions. We believe different patterns of NDVI changes were closely linked with these regions’ policy-oriented differences in urbanization dynamics, which also highlighted the importance of implementing a sustainable regional growth policy.