A recently published article highlights the impact of climate, urban form, and tree traits on the cooling effect of urban trees. The researchers synthesize data from 182 studies across 110 cities in 17 climate zones. It’s an excellent study, but its findings need adaptation for hot-humid-dry regions.
With over 20 years of experience designing outdoor environments in Gulf cities, we see firsthand how climate and culture shape urban cooling strategies. The Gulf’s extreme conditions—intense heat, hyper-aridity, and high humidity—present unique challenges. While global research on urban forestry often overlooks this specific climate, its principles can be tailored to create effective, region-specific solutions for pedestrian heat mitigation.
Research findings must be tailored before applying to the dry-hot-humid climate.
The research categorizes climates into four types: tropical, temperate, continental, and arid. It’s tempting to apply the “arid” category to Gulf cities, however arid climates vary significantly in temperature and humidity. Cities like Riyadh, Doha, and Dubai experience extreme heat coupled with high humidity. This combination complicates urban cooling because trees cool more effectively as temperatures rise—but their cooling power diminishes as humidity increases. Effective strategies for mitigating humidity’s negative impact are critical for Gulf cities.
Mitigating humidity is critical for urban cooling in Gulf cities. Both shade and ventilation are important.
The study underscores that “background climate, urban morphology, and tree traits are highly interconnected” in determining cooling efficacy. This means that a simplistic “plant more trees” approach does not guarantee optimal cooling. The design process requires a scientific approach that integrates simulation tools, urban thermal comfort expertise, and landscape architecture. NatureCulture and the Green Different Network specialize in this, with urban thermal comfort specialist Dr. Nihal Al Sabbagh advising our designers on the cooling efficacy of different landscape strategies.
The tree garden is the most effective landscape typology for urban cooling.
While no single solution fits all cases, the tree garden typology is a particularly effective cooling system for hot-humid climates. This approach spaces trees closely, encouraging tall, slender trunks with high canopies. The open under-canopy promotes ventilation, reducing humidity buildup.
Key benefits of tree gardens:
-
Pedestrian-Level Cooling: High canopies keep sun-heated leaf surfaces away from pedestrians, while close spacing enhances ground-level shading.
-
Improved Airflow: Elevated canopies allow better ventilation, preventing humid air from getting trapped beneath dense foliage.
-
Optimized Shading: Dense trunks and a high Leaf Area Index (LAI) block solar radiation, reducing ground-level heat absorption.
A scientific and culturally informed approach to urban cooling is essential for Gulf cities. Traditional tree gardens align with the region’s environmental conditions and can play a contemporary role is today’s cities. Two projects by NatureCulture demonstrate proof-of-principle: Dubai One Central and The Makers District in Abu Dhabi.
With the right strategy, Gulf cities can transform their urban environments. A holistic, evidence-based design process is the key to delivering cooler, more livable spaces.
