Chinese cities, accounting for approximately 85% of the nation’s carbon emissions, face a pressing need for innovative solutions to reduce urban CO2 levels. Conventional emission reduction measures alone fall short of addressing the challenge given China’s rapid economic growth. Urban greening, including roof greening, presents a promising strategy to establish carbon sinks within densely populated areas, offering potential climate mitigation benefits.Fertile lands in China are largely occupied by agricultural or natural vegetation, making additional land-based carbon sinks difficult to establish. Similarly, desert greening faces significant technical and financial barriers, as well as water resource constraints. Urban greening on open land is limited by space availability, leaving rooftops as an underutilized resource for carbon offset initiatives.

To explore this potential, researchers from Shenzhen University conducted a study utilizing large-scale Earth observation data from 2020. The team evaluated the carbon sink potential of roof greening under two scenarios: grass planting and shrub planting. They assumed optimal conditions for technology, management, and investment. The analysis revealed that roof greening in major Chinese cities could contribute significantly to offsetting urban carbon emissions.

Key findings include:

– Roof greening could create a potential carbon sink of approximately 52.2 Tg C a-1 for grass planting and 41.0 Tg C a-1 for shrub planting.

– This would directly offset 2.4% – 3.0% of urban carbon emissions, equivalent to fully offsetting household emissions.

– Economic benefits from carbon tax savings are estimated between $19.6 billion and $24.9 billion annually.

– Roof greening reduces urban thermal environments and energy demand, particularly for air conditioning and heating.

– Prioritizing low-rise and middle-low-rise roofs captures over 90% of the carbon sink potential.

The study’s conclusions highlight the role of roof greening in advancing China’s carbon neutrality goals and Sustainable Development Goals (SDGs). Additionally, the methodology used for estimating roof greening’s carbon sink potential could be adapted to cities worldwide, providing a scalable solution for global climate mitigation efforts.

The research was published in Science Bulletin, a multidisciplinary journal managed by the Chinese Academy of Sciences (CAS) and co-sponsored by CAS and the National Natural Science Foundation of China (NSFC).