Cities in the Global South are more vulnerable to extreme heat due to a shortage of cooling green spaces, according to new research. The study reveals that these cities have only 70% of the “cooling capacity” provided by urban greenery compared to cities in the Global North. Published in *Nature Communications*, the paper titled “Green infrastructure provides substantial but unequal urban cooling globally” highlights the importance of urban green spaces in mitigating heat-related risks.
With rising temperatures and the “urban heat island” effect, cities are becoming hotter than rural areas, leading to increased heat-related illnesses and deaths. Urban green spaces can significantly reduce these risks by cooling outdoor environments and offering essential refuges. The research, led by an international team from universities including Nanjing, Exeter, Aarhus, and North Carolina State, emphasizes the “vast potential” to enhance urban cooling in the Global South and reduce inequality.
“Urban greenery is an effective way to combat the fatal effects of extreme heat and humidity,” said Professor Tim Lenton of the Global Systems Institute at the University of Exeter. “Those most affected by climate change are often in the slums of Global South cities, like the hottest parts of India. Our analysis shows that green spaces can lower surface temperatures by about 3°C during warm seasons—a critical difference during extreme heat.”
The cooling effect of urban green spaces, particularly urban forests, is due to shading and transpirational cooling (evaporation of water). The study utilized satellite data from the world’s 500 largest cities to assess “cooling capacity”—how much urban green spaces reduce a city’s surface temperatures.
The top ten cities for cooling capacity are all in the U.S., with Charlotte and Raleigh-Durham leading, followed by Kansas and Baltimore. While low population density in these cities can lead to urban “sprawl,” it also provides cooling benefits through green spaces. Mogadishu in Somalia ranks lowest in cooling capacity, followed by Sana’a in Yemen and Rosario in Argentina. Chicago is the only U.S. city on the list with cooling capacity below 1°C.
The Global South, which includes Africa, Latin America, and much of Asia, faces the greatest risk from extreme heat. A previous study predicted that current climate policies would leave more than a fifth of the global population exposed to dangerously high temperatures by 2100, with India and Nigeria being the most affected.
The new study evaluated population density and location to estimate the “cooling benefit” received by the average resident, noting that green areas are often concentrated in wealthier parts of a city. Professor Chi Xu of Nanjing University pointed out that residents in Global South cities experience a cooling benefit of just 2.2°C, compared to 3.4°C in the Global North. This disparity is largely due to the quantity of vegetation, but also to the more effective management of green spaces and different tree species in the Global North.
Professor Jens-Christian Svenning of Aarhus University emphasized that this nature-based solution could be significantly improved across the Global South, helping to alleviate future heat stress for billions of people. Professor Rob Dunn of North Carolina State University added that while regreening cities can be costly in the short term, it is crucial for making cities livable in the near future. He suggested solutions like ground-level green spaces, vertical and rooftop gardens, or even urban forests to protect city dwellers from extreme heat.
