A systematic comparison of urban and peri-urban vegetation greenness in 955 global major cities

Urbanization results in the conversion of vegetated land into impervious surfaces, substantially altering terrestrial ecosystems. To comprehensively assess these impacts, this study conducted a global comparative analysis of vegetation greenness between urban and peri-urban areas in 955 major cities from 2001 to 2019. Using satellite-derived Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) data, this study examined both the absolute levels and temporal trends of vegetation greenness. The results showed that the ΔEVI and ΔNDVI (urban EVI or NDVI minus peri-urban EVI or NDVI) differed greatly by cities, and the method used to define urban and peri-urban areas. In most cities, the ΔEVI and ΔNDVI were negative, indicating lower vegetation greenness in urban cores. From 2001–2019, the average urban EVI and NDVI of these 955 cities decreased significantly (p < 0.01), while the average peri-urban EVI and NDVI increased significantly (p < 0.01), leading to a growing urban and peri-urban vegetation disparity. Furthermore, ΔEVI and ΔNDVI, along with their trends, generally decreased as the distance from the city increased, stabilizing when the distance exceeded 15 km. The presence of impervious surfaces and water bodies in peri-urban areas contributed to higher mean values and trend slopes of ΔEVI and ΔNDVI. The ΔEVI and ΔNDVI, along with their trends derived from high-resolution impervious surface data were generally lower than those from moderate-resolution land cover data. These findings contribute to our understanding of the impact of urbanization on vegetation greenness and provide a scientific foundation for urban planning and ecosystem management.