Global South Cities Face Greater Heat Risks

As climate change accelerates, cities worldwide are grappling with rising temperatures, but new research highlights a stark disparity: cities in the Global South are far more vulnerable to extreme heat due to a significant lack of cooling green spaces. These cities have just 70% of the “cooling capacity” provided by urban greenery compared to cities in the Global North, according to a recent study.

The study, led by an international team from Nanjing, Exeter, Aarhus, and North Carolina State universities, underscores the growing risk of heat-related illnesses and deaths in the Global South, where urban heat island effects—areas in cities that are hotter than surrounding rural areas—exacerbate already high temperatures. The findings suggest there is vast potential to enhance urban cooling through green spaces, which could play a crucial role in reducing health inequalities in these regions.

GLOBAL DISPARITIES IN COOLING CAPACITY

The study utilized satellite data from the world’s 500 largest cities to evaluate the “cooling capacity” of urban green spaces. The results revealed a significant gap between cities in the Global North and South. All of the top ten cities for cooling capacity are located in the USA, with cities like Charlotte and Raleigh-Durham leading the list, followed by Kansas and Baltimore.

In contrast, Mogadishu in Somalia ranks as the city with the lowest cooling capacity, followed by Sana’a in Yemen and Rosario in Argentina. Chicago is the only U.S. city to appear on the list of cities with the lowest cooling capacity, with a temperature reduction of less than 1°C.

IMPORTANCE OF URBAN GREEN SPACES

Urban green spaces, including parks, gardens, and urban forests, serve as vital cooling mechanisms in cities. They help mitigate the effects of extreme heat through shading and transpirational cooling, a process where water evaporates from plants, cooling the surrounding air. According to the research, the cooling effect of these green spaces can reduce surface temperatures by approximately 3°C during warm seasons—a difference that could prove lifesaving during extreme heat events.

“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.”

THE UNEQUAL COOLING BENEFIT

The research also explored the “cooling benefit” experienced by the average citizen, factoring in population density and location within a city. Findings indicate that residents of the Global South not only live in cities with lower overall cooling capacity but also receive less cooling benefit per capita.

Professor Chi Xu of Nanjing University pointed out that “the cooling benefit for an average resident in the Global South is 2.2°C, compared to 3.4°C for a city dweller in the Global North.” The discrepancy is attributed mainly to the quantity and efficiency of vegetation. Management practices and tree species selection in the Global North are cited as factors contributing to the better cooling efficiency.

THE WAY FORWARD: ENHANCING URBAN GREEN SPACES

The study’s findings highlight an urgent need to invest in urban greenery in the Global South. While creating and maintaining green spaces can be costly in the short term, the long-term benefits in terms of health and livability are undeniable.

Professor Jens-Christian Svenning from the Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) at Aarhus University emphasized 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.”

However, the process of “regreening” cities is not without challenges. Professor Rob Dunn of North Carolina State University acknowledged the difficulties: “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.”

To enhance urban cooling, cities could explore various green space solutions, such as ground-level parks, vertical gardens, rooftop gardens, and even urban forests. These green spaces not only help cool the environment but also provide recreational areas and improve the overall quality of life for city residents.

A CALL TO ACTION FOR THE GLOBAL SOUTH

As temperatures continue to rise globally, the need for effective urban cooling strategies in the Global South has never been more critical. Investing in urban green spaces is a promising solution to mitigate the effects of extreme heat, reduce health risks, and bridge the gap in climate resilience between the Global North and South. The challenge now lies in implementing these solutions swiftly and effectively to protect vulnerable populations from the growing threat of heat-related illnesses and deaths.