On a sweltering summer day, few things are as soothing as a stroll through a botanical garden. But these gardens are more than a peaceful oasis. In the face of global warming and rising temperatures, botanical gardens can play a crucial role in cooling the streets around them.
Researchers at the University of Surrey in the U.K. found that botanical gardens are the most effective natural cooling zones in urban areas during extreme heat waves. They hope the findings will help city leaders plan cooler urban environments amid the climate crisis.
What the Researchers Found
The team conducted a meta-analysis of more than 200 studies that measured how different green and blue spaces cool streets during intense heat waves. They found botanical gardens to be the most effective natural coolers in cities, lowering air temperatures by about 5°C on average. That beat wetlands (4.7°C) and rain gardens (4.5°C), which ranked second and third.
The study also found that green walls, street trees, and even playgrounds significantly lower urban temperatures, The Guardian reported.
Professor Prashant Kumar, director of the Global Centre for Clean Air Research at the University of Surrey, says scientists long suspected that greenery and water could cool cities. But this analysis offers the most comprehensive picture yet: botanical gardens are unique ecosystems that provide everything streets need to stay cooler — from shade-giving trees to evaporating water that chills the air.
The study recommends basing urban cooling networks on smart planning of blue (water) and green (plant) infrastructure.
The meta-analysis showed that larger green spaces produce stronger cooling effects on streets. It also found that linking green zones with green corridors would better protect cities from extreme heat.
“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
