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​Johannesburg is facing a heat island effect due to the absorption and retention of heat by buildings, pavement, and other human-made structures. This is likely to increase energy consumption and air pollution for vulnerable residents. However, the municipality is hard at work researching and implementing a variety of strategies to mitigate the impact of the heat island effect. Mzukisi Gwata, the principal specialist in the City’s climate change adaptation unit, says Johannesburg is one of the major cities facing increased heat exposure, especially within poorer communities.

"We are now making conscious efforts to be able to respond to heat threats because they form part of the Environment and Infrastructure Services Department’s (EISD) Climate Action Plan (CAP)," Gwata explains.

The City’s CAP outlines how the municipality works towards achieving its emissions reduction targets to reduce the vulnerability of its citizens to the harsh impacts of climate change.

The heat island effect is a phenomenon in which metropolitan regions across the world experience higher temperatures than surrounding rural areas due to heat absorption and retention by buildings, pavement, and other man-made structures. This can lead to a range of severe consequences for human health and the environment, such as increased energy consumption for cooling buildings, exacerbate air pollution and smog formation, and affect human health by intensifying heat-related illnesses.

It can also disrupt ecosystems and affect biodiversity, as many plant and animal species are sensitive to temperature changes. The lack of vegetation and green spaces in urban areas reduces the cooling effect of evaporation and the shade provided by trees and plants.

"Heat waves have different effects on different people. The heat you have during the day is manageable, but the worst is when your temperature doesn’t drop at night to allow you to sleep. There are people who have underlying conditions and children who are not fully developed and not yet able to regulate their body temperatures," Gwata explains.

Studies on more densely populated and informal settlements have shown there is a real cause for concern in terms of increased heat because their living spaces don’t absorb heat but rather regenerate it. Results indicate that these areas have little to no trees and that those that are there are old and can’t provide much relief.

"The increased heat is as a result of buildings that re-emit it. On the other hand, if we move more towards the south of the City there are larger open spaces that accumulate less heat," Gwata says.

He notes that people living in informal settlements are more susceptible to the heat island effect because they do not have windows, air conditioning, or access to tap water in their homes, which means they do not have the adaptable capacity to withstand the increased heat and cool themselves down.

Gwata says the municipality and several stakeholders have engaged in citizen targeted science campaigns and studies to map out neighbourhoods and communities that are more directly impacted by the rising temperatures, including Alexandra, Kliptown, and Braamfontein.

Importantly, he says the City has, since the inception of its research, implemented some heat-mitigating elements, such as planting more trees through Johannesburg City Parks and Zoo (JCPZ).
"JCPZ has been allocated a budget to plant over 10,000 trees a year throughout the City. This may seem like a small effort, but it makes a noticeable difference, especially in communities that do not have adaptable capacities," he says.
The City has also petitioned the World Bank to participate and assist with the management of the heat island effect in Johannesburg.
"We have since created more awareness on the issue of increasing temperatures, and we as a unit will continue with policy making and researching the effects of climate change. This will enable us to bring issues and concerns to the fore that we discover in the science of climate change, and it then becomes a City initiative to find solutions to these problems," Gwata explains.

He says addressing the heat island effect is a crucial step towards creating more sustainable and liveable urban environments, promoting energy efficiency, and mitigating the impacts of climate change.

Residents can take steps to reduce their own contributions to the heat island effect by choosing energy-efficient appliances and reducing their use of air conditioning and single-use plastics.

Written by Sascha-Lee Joseph