Project Statement

Megacities exacerbate carbon emissions due to intensified building energy use and urban heat islands. Urban green spaces offer dual carbon benefits: acting as direct carbon sinks and indirectly reducing emissions by lowering building energy demand through localized cooling. This study analyzes Beijing’s urban park ring using random forest analysis to quantify the impact of landscape indices and green space attributes on carbon reduction.  Results indicate that cooling-driven reductions dominate carbon benefits. Under the proposed green space optimization scenarios, total carbon mitigation potential is projected to increase by 11.2%. The framework supports urban green spaces optimization for carbon management and climate resilience.

Project Narrative

Urban built-up areas, covering just 0.34% of global land in 2020, account for approximately 75% of global carbon emissions. In megacities like Beijing, the disparity is even more pronounced, with 90% of the city’s carbon emissions originating from its built-up areas. Amidst the urgency to mitigate climate change, reducing urban carbon emissions has become a critical priority. However, the carbon contribution of urban green spaces is often underestimated, especially their potential for indirect reductions through cooling effects.

Existing studies primarily emphasize the ecological services of green spaces, while overlooking their carbon reduction potential. Current accounting approaches for cooling-induced carbon mitigation remain underdeveloped, often relying on simplified energy models, lacking clear identification of indirect reduction pathways, and falling short of multi-scale, multi-factor analyses to reveal underlying mechanisms. Consequently, the strategic positioning of green infrastructure in urban carbon neutrality pathways remains ambiguous, hindering effective optimization and deployment.

This study addresses these gaps by focusing on the urban park ring in Beijing, aiming to quantify both direct carbon sink and indirect cooling-induced carbon reduction. We employ a comprehensive methodological framework integrating remote sensing data analysis, numerical modeling, EnergyPlus simulations, and random forest machine learning. This framework enables precise estimation of green space–induced carbon reductions by quantifying their cooling range and intensity, and integrates an urban-scale building emission model to capture energy-use responses. By tracing the cooling–energy–carbon pathway, the study aims to quantify actual carbon reductions and uncover the multi-factor mechanisms that drive them.

Results indicate that green spaces, occupying 20.5% of the carbon emissions in the study area, offset 0.31% of carbon emissions through direct sink and 10.6% through cooling-induced carbon reduction, highlighting the dominant role of cooling effects. The analysis reveals that building type, green patch size, and edge density significantly affect the cooling-induced carbon reduction efficiency. On a global scale, the potential cooling-induced carbon reduction from urban green spaces is estimated to reach 2.06 billion tons annually.

Building upon these findings, we propose three macro strategies — connecting green networks, establishing ventilation corridors, and optimizing green patch configurations — and four targeted design strategies — enhancing energy management, optimizing plant communities, increasing vertical greening, and expanding blue-green spaces. Implementation of these strategies could increase the green space area by 4.3 km², elevate vertical greening coverage, and enhance overall carbon contributions by 11.2%.

This study focuses on cooling-induced carbon reduction from urban green spaces, refines the carbon accounting framework at the urban scale, and demonstrates the significant carbon reduction potential of optimized green infrastructure. The proposed framework not only informs targeted urban green spaces design but also provides actionable insights for integrating green infrastructure into urban carbon neutrality strategies, effectively transforming green spaces into pivotal components of urban carbon management systems.