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. Amid the current global warming crisis, with temperatures soaring, botanical gardens could play a crucial role in alleviating heat in the surrounding streets. Researchers from the University of Surrey in the UK were the first to discover that botanical gardens are the most effective natural cooling zones for urban spaces during extreme heat waves. They hope their findings will assist city planners in designing urban environments that can withstand the climate crisis.
The university team conducted a meta-analysis of over 200 studies that provided data on cooling factors in streets during intense heat waves. They found that botanical gardens emerged as the most effective natural “coolers” in cities experiencing extreme temperatures, helping to lower air temperatures by an average of 5 degrees Celsius. This performance outpaced wetlands (4.7 °C) and rain gardens (4.5 °C), which rounded out the top three cooling zones.
Scientists also 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, researchers 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 necessary 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 confirmed that the larger the area of green spaces, the more powerful the cooling effect on streets. They 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 Zones by Average Cooling Effect on Cities:
Botanical Gardens: -5.0 °C
Wetlands: -4.7 °C
Rain Gardens: -4.5 °C
Green Walls: -4.1 °C
Street Trees: -3.8 °C
Urban Farms: -3.5 °C
Parks: -3.2 °C
Reservoirs: -2.9 °C
Playgrounds: -2.9 °C