Roof greening in major Chinese cities possibly afford a large potential carbon sink
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Roof greening in major Chinese cities possibly afford a large potential carbon sink (details see Science Bulletin)
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In China, about 85% of the carbon emissions stem from cities, with large cities being the main contributors. Considering China’s economic development, relying on only conventional emission reduction measures is insufficient. Various studies have shown that large-scale greening (e.g. afforestation or urban greening) can create carbon sinks, which offset CO2 emissions. However, in China, fertile lands (especially suburbs) have been occupied by agricultural lands and natural vegetations, and incorporation of additional carbon sinks on these lands is particularly difficult. Furthermore, greening in deserts has large technical difficulties and economic costs and could strain the water resources. Open lands in cities are limited, and thus, conducting wide-scale urban greening is impossible. Fortunately, cities have abundant roof resources, which could be utilised to resolve this dilemma. Roof greening is an effective measure for reducing requisite investment, saving land and increasing green spaces in the limited urban areas, thereby contributing to climate change mitigation.
Therefore, a research team from Shenzhen University used large-scale Earth observation data from 2020 and scenario analysis (grass or shrub planting scenarios) to explore the possible carbon sinks of roof greening in all major Chinese cities under ideal conditions (assuming actual roof greening can achieve optimal capacity of natural grass and shrubs under excellent greening technology, management and investment conditions), and evaluated its contribution to carbon neutrality.
Their results show that roof greening in all major Chinese cities could possibly afford a large potential carbon sink (approximately 52.2 Tg C a-1 for grass planting scenario and 41.0 Tg C a-1 for shrub planting scenario), directly offsetting about 2.4%–3.0% of the urban carbon emissions (equivalent to fully offsetting the household emissions), with great potential for harvesting the carbon tax (about 19.6 -24.9 US$ billion per year) and mitigating the thermal environment and energy consumption (e.g. reducing the demand for air conditioning and heating). In addition, prioritizing greenery on low-rise roofs and middle-low-rise roofs can harvest the most carbon sinks (over 90%).
Their findings provide novel insight for China's carbon neutrality goals and the Sustainable Development Goal. Moreover, their study methods (estimation carbon sink of roof greening) can be migrated to other cities around the world, which contributes to global climate mitigation.
The study was published in Science Bulletin, the multidisciplinary academic journal supervised by the Chinese Academy of Sciences (CAS) and co-sponsored by the CAS and the National Natural Science Foundation of China (NSFC).
Journal
Science Bulletin
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