Cities in the Global South are facing a pressing challenge – extreme heat. Startling research reveals that these cities lack the crucial cooling green spaces that their Global North counterparts benefit from. The study shows that Global South cities only possess 70% of the “cooling capacity” provided by urban greenery in the Global North.
With temperatures on the rise and the exacerbation of the “urban heat island” effect, cities are experiencing higher temperatures than rural areas, leading to a sharp increase in heat-related illnesses and fatalities.
Urban green spaces have the power to mitigate these risks by cooling down outdoor environments and offering essential sanctuaries. A recent international research effort, spearheaded by Nanjing, Exeter, Aarhus, and North Carolina State universities, highlights the vast potential for enhancing urban cooling in the Global South and addressing inequality.
“Urban greenery is a really effective way of tackling what can be fatal effects of extreme heat and humidity,” said Professor Tim Lenton of the Global Systems Institute at the University of Exeter.
“Currently, the people dying due to climate change are often in the slums of cities in the Global South, such as the hottest parts of India. Our analysis suggests green spaces can cool the surface temperature in the average city by about 3°C during warm seasons – a vital difference during extreme heat.”
The cooling effect of urban green spaces, particularly urban forests, is crucial for city environments. A new study utilized satellite data on the world’s 500 largest cities to evaluate the “cooling capacity” of urban green spaces. This capacity refers to the extent to which these green areas can mitigate a city’s surface temperatures.
Surprisingly, all of the top ten cities for cooling capacity are located in the USA, with Charlotte and Raleigh-Durham taking the lead, followed by Kansas and Baltimore. This demonstrates the significant impact of urban greenery in cooling urban environments. Interestingly, many US cities with lower population density are able to benefit from extensive green spaces, resulting in a noticeable cooling effect.
On the other hand, Mogadishu in Somalia stands out as the city with the lowest cooling capacity, followed by Sana’a in Yemen and Rosario in Argentina. Even Chicago, a prominent US city, ranks among the lowest in cooling capacity. This information underscores the importance of prioritizing urban green spaces for cooling and improving city environments.
The Global South – encompassing Africa, Latin America, and much of Asia – faces the greatest risk from extreme heat.
A concerning study revealed that if current climate policies persist, over a fifth of the world’s population will endure dangerously hot temperatures by 2100, with the most vulnerable populations residing in India and Nigeria.
In a recent study, researchers evaluated population density and location to determine the “cooling benefit” that the average citizen receives. They found that green areas, which provide cooling relief, are often concentrated in wealthier parts of a city.
Professor Chi Xu of Nanjing University expressed, “Not only do Global South cities lack adequate cooling capacity, but the average resident receives only a 2.2°C cooling benefit compared to the 3.4°C benefit for city dwellers in the Global North”.
“The differences are mostly due to quantity of vegetation, but the efficiency of cooling is also better in the Global North – possibly due to management of green spaces and different tree species.”
Professor Jens-Christian Svenning of the Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) at Aarhus University said: “The good news is that this nature-based solution to cooling can be substantially improved across the Global South, helping to tackle future heat stress for billions of people.”
Professor Rob Dunn, of North Carolina State University, said: “It won’t be easy to regreen cities. It can be expensive in the short-term. Yet, it will be key to making cities liveable in the immediate future. Also, the key will be working to prevent the loss of green space in those cities that have it, or at least that have a little.
“Changes could include ground-level green spaces and vertical and rooftop gardens, or even forests, to help protect city people from extreme heat.”
Journal reference:
- Yuxiang Li, Jens-Christian Svenning, Weiqi Zhou, Kai Zhu, Jesse F. Abrams, Timothy M. Lenton, William J. Ripple, Zhaowu Yu, Shuqing N. Teng, Robert R. Dunn & Chi Xu. Green spaces provide substantial but unequal urban cooling globally. Nature Communications, 2024; DOI: 10.1038/s41467-024-51355-0