Global urban environment reveals uneven increase in vegetation growth enhancement

The globally invasion of urban impervious surface area (ISA) to vegetation cover is increasing, continuous time and global spatial scales of vegetation response to urbanization is a snapshot of future responses to climate change in non-urban biological ecosystems. However, the impacts of urbanization on vegetation growth in long time series have not been clearly verified globally. In this study, using a conceptual framework and remote sensing data, we explored global urbanization imprint on vegetation growth across the entire urbanization intensity () during 2000-2018. We found that the vegetation declines with urbanization intensity globally, and more cities appeared vegetation decline, from 96.85% of decline cities in 2000 increased to 97.29% in 2018. But prevalent vegetation growth enhancement appeared in global urban environment, and which is rising over time (i.e., the growth of the remaining vegetation patches can offset the vegetation reduction due to the replacement of original land surfaces by impervious built-up, and the offset impact form 52.5% increased to 57.1%). In addition, the global urban environment reveals uneven increased in vegetation growth enhancement. First, interannual variation of the vegetation response to urbanization are not uniform by years, such as, in 2013, 2015, and 2001, they had greater interannual variation than other years. Second, uneven vegetation growth enhancement also occurred in various regions. Different latitudinal gradients and climate type regions had variations in vegetation growth distribution and trends, such as, high latitudinal gradients, and the Cs (Temperate region: Dry Summer), Df (Cold region: Without Dry Season) climate zones had a noticeably stronger vegetation growth enhancement generally. Our research on urban vegetation will help identify future vegetation changes under global climate change and is an important science for the earth response to climate change.