Mega-cities dominate China's urban greening

TL;DR

This study uses nano-satellites to assess urban tree coverage across Chinese cities, revealing significant increases especially in mega-cities, but also highlighting uneven greening efforts.

Contribution

It introduces a novel satellite-based method for monitoring urban tree dynamics at a national scale in China.

Findings

Approximately 11% of urban areas covered by trees in 2019.

76% of cities increased tree cover since 2010.

Mega-cities like Beijing and Shanghai saw twice the growth compared to others.

Abstract

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.