“Greening the Urban Jungle: How Green and Blue Infrastructures are Cooling Cities Worldwide”
Urban heatwaves have become a pressing issue globally, exacerbated by urbanization and global warming. Hong Kong, in particular, has been experiencing record-breaking high-temperature days. To address this challenge, Prof. Hai GUO from The Hong Kong Polytechnic University and global researchers have conducted a groundbreaking study on the effectiveness of green interventions in cooling urban heat across various regions.
The study, published in The Innovation, highlights the importance of green-blue-grey infrastructure (GBGI) in mitigating urban heat. GBGI includes green infrastructures like trees and grass, blue infrastructures such as pools and lakes, and grey infrastructures like green walls and roofs. The research team found that botanical gardens, wetlands, green walls, street trees, and vegetated balconies are the most efficient in air cooling globally.
Regional variations were observed in the effectiveness of GBGI for cooling urban heat. In Europe, Asia, North America, and Australia, the overall cooling effect of GBGI ranged from 9.63°C to 18.9°C. Asian cities, in particular, saw significant temperature reductions with constructed grey infrastructures like roof gardens and pergolas. For example, roof gardens in Singapore achieved a temperature reduction of 17.7°C, while pergolas and green roofs in Japan and South Korea lowered temperatures by 16.2°C and 10.8°C, respectively.
In Mainland China cities, botanical gardens, wetlands, green walls, and attenuation ponds were found to be effective in reducing temperatures by up to 10°C. Hong Kong’s unique natural environment, with its network of oceans, rivers, wetlands, and reservoirs, has made it a prime location for implementing GBGI. The city’s “Shining City Project” aims to enhance urban green space through initiatives like greening riverbanks and planting trees in government venues.
The study’s findings can assist policymakers and urban planners in prioritizing effective interventions to combat urban overheating. A nine-stage framework has been introduced to guide the implementation of GBGI, emphasizing stakeholder engagement, feasibility studies, design, policy development, monitoring, and evaluation. Prof. Guo stressed the importance of adopting a holistic approach to GBGI implementation to address sustainability goals effectively.
Overall, the study underscores the critical role of green interventions in creating sustainable and resilient cities in the face of urban heatwaves and climate change. By prioritizing green-blue-grey infrastructure, cities can mitigate the impact of rising temperatures and promote community resilience in the face of environmental challenges.