On a sweltering summer day, few things are as soothing as a stroll through a beautiful botanical garden. But these gardens are more than just a peaceful oasis. In the face of global warming and rising temperatures, botanical gardens can play a crucial role in combating the heat on surrounding streets.
Researchers from the University of Surrey in the UK were among the first to discover that botanical gardens serve as the most effective natural cooling zones for urban spaces during extreme heat waves. The scientists hope their findings will assist city leaders in planning urban environments amid the climate crisis.
What the Researchers Found
The university team conducted a meta-analysis of over 200 studies that included data on cooling factors for streets during intense heat waves. They found that botanical gardens were the most effective natural “coolers” for cities experiencing extreme temperatures, helping to lower air temperatures by an average of 5 degrees Celsius. This outperformed wetlands (4.7 °C) and rain gardens (4.5 °C), which rounded out the top three cooling zones.
The researchers discovered that even green walls, street trees, and playgrounds significantly reduce urban temperatures, as reported by The Guardian.
According to Professor Prashant Kumar, director of the Global Centre for Clean Air Research at the University of Surrey, scientists have long suspected that greenery and water could effectively cool cities. However, this study provided the most comprehensive picture yet. They found that botanical gardens represent unique ecosystems that contain everything needed to shield streets from heat: “from shade-giving trees to evaporating water that cools the air.”
The researchers noted that creating a cooling network in cities should be based on smart planning of blue (water) and green (plants) infrastructure.
The meta-analysis demonstrated that the larger the area of green spaces, the more powerful the cooling effect on streets. The scientists also found that cities would be better protected from extreme heat if green zones were connected by green corridors.
“If we implement even some of our findings, cities will become more resilient, and their residents will be healthier and happier,” said Professor Kumar.
Ranking of Green Spaces by Average Cooling Effect on Cities
- Botanical Gardens: up to -5.0 °C
- Wetlands: up to -4.7 °C
- Rain Gardens: up to -4.5 °C
- Green Walls: up to -4.1 °C
- Street Trees: up to -3.8 °C
- Urban Farms: up to -3.5 °C
- Parks: up to -3.2 °C
- Reservoirs: up to -2.9 °C
- Playgrounds: up to -2.9 °C