Rapid urbanization and meteorological changes are reshaping the urban vegetation pattern in urban core area: A national 315-city study in China

Urban vegetation takes on the responsibility of improving the urban environment and human wellbeing. However, the changing pattern and its driving mechanism are still not well understood at the national scale, especially in China under nearly 20 years-long rapid urbanization. In this study, for urban core area in 315 cities, over 18,000 high-resolution remote sensing images across 18 years were used to detect the spatiotemporal changes of urban vegetation and furtherly explore the interaction and independence of rapid urbanization and meteorological change. We found that, urban vegetation coverage decreased from 12.23 % to 5.91 % (-0.35 % per year) in 2003 to 2020. Urban vegetation per capita presented a steeper decline by 68 % (-0.51 m2 per capita per year) from 18.94 m2 in 2003 to 9.83 m2 in 2020. Spatially, the northwest and central-south zone decreased faster at the regional scale, and small cities contribute the higher decreasing rate. From 2003 to 2020, urbanization is the significant negative factor which contribute to 29.6 % of the reduction, and the meteorological factors do not affect urban vegetation change. Also, we found that the temporal pattern of urban vegetation change could be separated into two stages, including a rapid decline stage (2009-2020) and a progressively declining stage (2003-2008), each has its own driving mechanism. From 2003 to 2008, the decline in urban vegetation had insignificant relationship with meteorological changes and rapid urbanization. However, from 2009 to 2020, urbanization became the most critical factor to affect the urban vegetation, the contribution of urbanization rises to 30.3 %, meteorological factors contribute 14.3 % to the variation (r2 = 0.52). A growing crisis awareness of the rapid decline (especially in 2009 to 2020) of urban vegetation should return to the public scene, and these findings may provide some essential suggestions for securing this urban ecological barrier.