A Threshold‐Free Clustering Framework Disentangles Policy‐Linked Greening From Urbanization‐Driven Browning in the Yangtze River Delta of China

Abstract Accurately characterizing grid‐level vegetation dynamics in urban agglomerations remains challenging due to high spatial heterogeneity and complex temporal responses to urbanization. We developed a threshold‐free clustering framework that integrates the LinCoIndex and structural similarity (SSIM) index to address this issue. Applied to the Yangtze River Delta urban agglomeration in China, it reveals three findings that challenge conventional threshold approaches: (a) L‐shaped urbanization‐driven browning in new urban areas versus V‐shaped policy‐linked greening in urban cores, with a browning‐to‐greening transition around 2009–2011; (b) low‐vegetation footprints occupying only 30%–58% of urbanized area while impervious surface plus annual peak vegetation exceeds 100%; (c) above‐impervious canopy increasing from 10% to 48% through tree planting and high‐rise building restrictions, enabling the region to meet China's 43% urban vegetation coverage target. These results indicate that coordinated greening interventions can offset net vegetation loss under sustained urbanization pressure.