Cities will feel the heat from climate change

South Africa’s fast-growing urban areas are “ticking time-bombs” as rising temperatures from climate change unleash intense heat waves and create an urban heat island caused by building materials trapping and absorbing heat, says Alize Le Roux, a senior researcher at the African Futures and Innovation Unit at the Institute for Security Studies.

Research by the Council for Scientific and Industrial Research (CSIR) has found that the effect of urban heat islands can cause temperatures to climb by 3°C to 10°C.

“We’re unprepared because of the way we’ve been designing, constructing and planning our cities for the past decades,” Le Roux says. “We are seeing some of these newer designs, or newer neighbourhoods, that are incorporating green spaces, green roofs and permutable surfaces — not asphalt surfaces — where water can actually penetrate into the ground, creating more of a cooling effect.”  

But these measures that seek to make urban settings cooler and more resilient remain elusive in poorer areas. “These are more expensive interventions so it’s still very unequal in its rollout and its implementation,” she says.

On South Africa’s urban future, the CSIR’s Green Book, an online climate risk profiling and adaptation tool, expects the country to follow the trend of high population growth and urbanisation that has unfolded across the rest of the African continent. 

In 1960, Africa’s urban population was just 15% of the total population, but this figure surged to more than 40% in 2010 and is predicted to surpass 60% by 2050. Current projections indicate that an additional 19 million to 24 million people will be added to South Africa by 2050, with most of this growth confined to cities and towns.

South Africa’s urban areas are at risk of the urban heat island effect, said Tirusha Thambiran, a senior researcher at the CSIR. She described how the replacement of natural open spaces with buildings, roads and public infrastructure retains more heat and decreases runoff and soil infiltration of stormwater.

“The surfaces of these urban materials act as ‘heat traps’ while the compaction of settlements to accommodate high density populations restricts environmental ventilation, with additional loss of natural cooling services,” she said, adding how these built-up areas then become warmer than the surrounding more rural areas. 

“In the context of urbanisation and climate change, the occurrence of urban heat islands are likely to be exacerbated. This can have impacts on human health and pose risks for increased air pollution.” 

South Africa’s rural areas, Thambiran said, require rapid formal urbanisation to address immediate socioeconomic deprivation and to improve quality of life. “More than half of South Africa’s population lives in urban areas and research shows that this phenomenon will increasingly affect the livelihood of residents as the urban population grows. 

“Most of the country is projected to become hot and drier in the future towards 2050, with heat waves increasing in frequency and intensity. For those living in urban areas, heat waves will be exacerbated by the urban heat island,” she added.

Le Roux points out that according to the Green Book’s heat-stress matrix, 454 cities and towns face severe heat stress by 2050. Many are unprepared for the rising heat, she said. The matrix, which is based on a projected rise in very hot days — days above 35°C — combined with increases in heatwave days, shows that those that will be hardest hit are the expanding cities of Upington and Kimberley, Mahikeng, Bloemfontein and Botshabelo, Lephalale and Musina and Mbombela. 

“The vulnerable people in our communities who are specifically at risk are the younger children and older adults; those who are actually dependent on somebody who can help them cool down or stay hydrated. And then those people living in [informal] dwellings that are already a couple of degrees hotter and if you add that on top of a heatwave it becomes unbearable in those conditions … 

“If they have to go outside to find a cooling mechanism, and are not in a space that has a park or trees, or water for that matter, those people are extremely at risk. They’ve got no mechanism to cool themselves down and that’s something that’s really quite troubling,” Le Roux said, explaining how people reliant on public transport should have green spaces in their walkways to protect them from heat exhaustion.

Heat deaths in South Africa are severely under-reported, said Le Roux, describing how official records indicate that only 11 fatalities have been attributed to severe heat. But, in 2018, researchers studying excess deaths through temperature correlations found a high mortality burden associated with warmer weather. This research concluded that almost 30 000 deaths in the country were directly attributable to increased temperatures from 1997 to 2013, she said. 

“Many times it’s the underlying issue that’s put on the death certificate so we’re not very good at capturing the fact that people are succumbing to extreme heat,” said Le Roux.

Heat, she said, is sometimes underreported “because we are a naturally hotter country, so people are used to heat and it’s almost unseen. But if you look at the medical side of it, they would normally start gearing up for hospital visits when there is extreme heat”.

While big metros such as Cape Town, Johannesburg, Ekurhuleni and eThekwini have pledged to build urban climate resilience, many of the country’s smaller municipalities have severely limited resources, she said. 

“They’re struggling to do the basics in terms of service delivery and now on top of this, you’re adding that they should deliver in a climate-smart way that thinks about the next three decades and the future … So, some of the long-term planning has fallen behind.” 

Among city planners, in general, there is a lack of awareness about heat, said Le Roux. “All cities should look at the extent of heat in their municipality and then if they deem it to be a threat, they should draw up heat contingency plans so that it can kick into gear when the South African Weather Service warns them that they are about to experience a heatwave.”

Infrastructure should be protected against the damage of heat, she said. “We should  make our cities greener and incorporate passive design principles into our buildings — that should be non-negotiable — that you account for temperatures that are two to three times hotter than what you are currently experiencing, that you account for heat waves and the buildings should be places that protect people and do not contribute to the deterioration of health.

“Things like designing north-south orientated plots and ensuring that the flow of winds are prevailing through the city to have a bit of a cooling effect. Protecting our water resources is extremely important by rehabilitating the ecosystems and ecological infrastructure that is already in cities.”

According to Thambiran, increasingly nature-based solutions are viewed as climate adaptation responses to rising temperatures and urbanisation pressures. These aim to produce more resilient cities through integrating nature into conventional built infrastructure and building systems. 

Key interventions include the application of hybrid permeable-cool pavement and roof designs; bioswales to improve stormwater runoff and the protection of remnant natural open spaces. “Measures that are taken to reduce the urban heat island will produce the benefit of lower temperatures, helping to improve resilience during heatwaves.”

The use of climate models is crucial as these can be used in urban design studies of the current climate and also be used to project future climate, she said. “The CSIR has developed such a modelling capability that is able to simulate the urban heat island in South African cities, under present and future climate. These simulations of urban heat are used in conjunction with key characteristics of the city to generate options to cool the city.”

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Sheree Bega
Sheree Bega is an environment reporter at the Mail & Guardian.

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