Urban blue and green infrastructure (UGBI) integrates nature-based elements such as urban green spaces (urban and peri-urban forests or grasslands) and water bodies (lakes, rivers, wetlands or sea), within urban areas to provide various ecosystem functions and services including cooling.
A recent study led by former ARIES modeller Alba Marquez-Torres, now a researcher at Centre de Ciència i Tecnologia Forestal de Catalunya (CTFC), highlights UGBI’s potential to mitigate urban heat. The research was conducted in close collaboration with ARIES urban modeller Sudeshna Kumar and former BC3 researcher Celina Aznarez (now affiliated with Aarhus University). The study also benefited from the guidance of Darrel Jenerette from the University of California, Riverside.
Published in Urban Forestry & Urban Greening, this research examines the effects of UGBI across 12 US cities with diverse climates, offering crucial insights into strategies for mitigating the urban heat island (UHI) effect in a context of rising temperatures due to rapid urbanization and climate change.
The study evaluated more than 4,600 urban green spaces (UGS), analysing their shape, composition, and surroundings to explore how vegetation and water interact to mitigate heat and enhance resilience. Key factors influencing UGBI’s cooling effects include:
- Vegetation health and density: UGS with healthy, dense vegetation (NDVI > 0.4) reduced land surface temperatures (LST) by up to 3°C.
- Proximity to water: UGS within 4 kilometres of water bodies benefited from enhanced cooling due to vegetation-water interactions. The closer UGS are to water, the greater the cooling effect.
- Park size and shape: Larger UGS, particularly those around 350 hectares, showed the greatest cooling benefits. Complex shapes amplified this effect by improving airflow.
- Building interactions: Shorter buildings nearby slightly reduced land surface temperatures (LST), though this effect diminished for structures above 20 metres.
The findings highlight the importance of integrating UGBI into urban design strategies to combat heat and enhance climate resilience. Policymakers and planners can use these insights to :
- Prioritise large, densely and healthy vegetated parks near water for optimal cooling.
- Strategically distribute smaller green spaces to address urban hotspots.
- Combine UGBI with reduced impervious surfaces and thoughtfully planned building layouts to create sustainable urban environments.
This study underscores the value of interdisciplinary collaboration, combining GIS, statistical modelling, and ecological research to show how UGBI helps mitigate climate change and urban heat. You can access the full study here. For additional insights, a related paper published in Science of the Total Environment examines heat vulnerability disparities and environmental justice through ARIES technology.
