  Trees play a crucial role in urban environments, offering various ecosystem
services that contribute to public health and human well-being. China has
initiated a range of urban greening policies over the past decades, however,
monitoring their impact on urban tree dynamics at a national scale has proven
challenging. In this study, we deployed nano-satellites to quantify urban tree
coverage in all major Chinese cities larger than 50 km2 in 2010 and 2019. Our
findings indicate that approximately 6000 km2 (11%) of urban areas were covered
by trees in 2019, and 76% of these cities experienced an increase in tree cover
compared to 2010. Notably, the increase in tree cover in mega-cities such as
Beijing, and Shanghai was approximately twice as large as in most other cities
(7.69% vs 3.94%). The study employs a data-driven approach towards assessing
urban tree cover changes in relation to greening policies, showing clear signs
of tree cover increases but also suggesting an uneven implementation primarily
benefiting a few mega-cities.
