The rising temperatures across the globe are prompting an urgent need for cities, especially in the Global South, to adopt urban greening strategies. A recent study, conducted by an international group of researchers from Nanjing, Exeter, Aarhus, and North Carolina State universities, reveals a substantial difference in the cooling capacity provided by urban green spaces between the Global North and Global South. This critical disparity highlights the necessity for immediate action to combat the growing threat of heat-related illnesses and deaths, particularly in urban environments.
According to the study, cities in the Global South possess only 70% of the ‘cooling capacity’ offered by urban greenery compared to their counterparts in the Global North. As global temperatures continue to rise and urban heat island effects intensify, it becomes increasingly clear that cities are becoming significantly hotter than surrounding rural areas. This phenomenon poses a severe risk to public health and well-being.
Professor Tim Lenton from the Global Systems Institute at the University of Exeter emphasizes the vital role of urban green spaces in alleviating the effects of extreme heat and humidity. He states, “Urban greenery is a really effective way of tackling what can be fatal effects of extreme heat and humidity.” The research indicates that augmenting urban greenery can lower temperature levels by approximately 3°C, making a crucial difference during periods of intense heat.
Urban green spaces, such as parks, urban forests, and rooftop gardens, contribute significantly to cooling efforts. They do so through two primary mechanisms: shading and transpirational cooling, which occurs through the evaporation of water from plant surfaces. These natural spaces not only decrease surface temperatures but also enhance air quality, reduce energy consumption, and promote biodiversity.
The environmental benefits of urban greenspaces extend far beyond mere temperature regulation. They act as carbon sinks, sequestering carbon dioxide and helping to mitigate urban pollution. Additionally, these green areas enhance resilience against flooding by absorbing rainfall, which eases the burden on urban drainage systems. This multifaceted utility reinforces the need for cities, especially in the Global South, to prioritize urban greening initiatives.
The study’s findings were drawn from satellite data of the world’s 500 largest cities, shedding light on the potential for enhancing urban cooling capacities in the Global South and addressing systemic inequalities. Notably, all top ten cities for cooling capacity are located in the United States, with cities like Charlotte and Raleigh-Durham topping the list. In stark contrast, Mogadishu in Somalia ranks lowest, followed by Sana’a in Yemen and Rosario in Argentina. Moreover, the average resident in the Global South experiences a cooling benefit of merely 2.2°C from urban greenery, compared to 3.4°C for residents in the Global North. This discrepancy is largely attributable to differences in the quantity and management of vegetation, as well as variations in tree species.
Professor Jens-Christian Svenning of Aarhus University provides a positive outlook on the situation: “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.” While re-greening efforts may present challenges and require significant investment in the short term, they are essential for enhancing urban livability amid climate change.
Practical solutions for increasing urban greenery include expanding existing ground-level green spaces, implementing vertical and rooftop gardens, and taking measures to protect existing greenery from degradation and loss. For instance, cities such as Singapore and Melbourne have initiated successful greening programs that serve as models for urban development. These cities have invested in integrating green spaces into urban planning, thus improving public health, increasing property values, and fostering community engagement.
As urban centers grapple with persistent rising temperatures, green spaces must be recognized as indispensable components of urban planning. Not only do they offer immediate relief from heat, but they also promote long-term sustainability and environmental health. The imperative to invest in these natural cooling systems cannot be overstated, as they are crucial for ensuring the well-being of millions of people living in the Global South.
The call to action is clear: municipalities and governments worldwide must prioritize urban greening strategies to mitigate the adverse effects of climate change. By investing in urban green spaces, cities can improve air quality, enhance biodiversity, and ultimately create healthier, more resilient communities.
