Assessing spatial-temporal dynamics of urban expansion, vegetation greenness and photosynthesis in megacity Shanghai, China during 2000-2016

Vegetation plays an essential role in improving urban environments and enhancing the physical and mental health of residents. However, rapid urbanization has exerted complicated influence on vegetation conditions, which remain poorly understood. To assess the impacts of urbanization on the vegetation structure and function in the urban area, we quantified the changes in impervious surface area (ISA) and assessed the impacts of urbanization on vegetation greenness (enhanced vegetation index (EVI)), and gross primary production (GPP) in megacity Shanghai during 2000-2016. The results show that 38.0% and 28.0% decreasing trends of EVI and GPP occurred in peri-urban and rural areas due to land use and land cover conversion, whereas 2.8% and 4.6% increasing trends of EVI and GPP occurred in the central city during 2000-2016 in Shanghai. In addition, the enhancement of EVI and GPP owing to the indirect impact of urbanization increased as the impervious surface coverage (ISC) gradient rose and peaked when the ISC reached similar to 0.8, which compensated for vegetation loss by 24.6% and 17.0%, respectively. The compensation was more stable and significant in peri-urban areas than urban and rural areas. This study provides detailed data and insights on the impacts of urbanization on vegetation, which may help stakeholders to make better management plans for urban vegetation.