Geospatial Monitoring of Urban Dynamics and Urbanization Impacts on Urban Green Landscape in Megacity Beijing Using the National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) Nighttime Light Data and Landsat Imagery

Urbanization can lead to social and economic progress, but it also inevitably poses a threat to the urban environment and ecological systems, especially in a fast-growing metropolis.Quantifying spatiotemporal patterns of urban expansion and its impact can help optimize land use patterns and promote sustainable urban development.In this study, we propose a novel methodological framework that (1) incorporates a spatial statistics approach for extracting builtup areas and a comprehensive evaluation method for assessing landscape changes, from overall trends to detailed internal dynamics, and (2) aims to quantify urban dynamics and investigate their impacts on urban green spaces.The time-series National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suites (NPP-VIIRS) imagery and statistical data including geographic information system (GIS)-based analysis were used to calculate overall changes in urban land expansion speed and movement direction, respectively.The spatiotemporal characteristics of urban green landscape patterns (i.e., landscape-level and class-level metrics) were monitored with time-series Landsat images.The results indicate that urban areas have experienced rapid expansion, and the built-up area increased by 1008.75 km 2 in the past 20 years.The urban expansion indices -including the expansion rate, intensity, and changes in urban migration center of gravity -reveal a distinct spatial structure of urban growth.This pattern was marked by both leapfrog development and the contiguous expansion of existing urban areas.Between 1999 and 2021, the gravity center of urban land consistently shifted in various directions.The area of built-up land decreased by -1.86% from 2014 to 2021, resulting in negative growth.Urban expansion has significantly altered the landscape pattern of urban green spaces, leading to the increased degree of fragmentation of built-up lands and a reduction in landscape diversity.Overall, geospatial monitoring is crucial in understanding how urban