Yaoundé, the Cameroonian capital, is a vibrant, cosmopolitan city where green hills meet modern architecture, creating a harmonious blend of culture, history and urban dynamism. The city has expanded significantly over the years because of urbanisation – its population has grown from 59,000 in 1957 to nearly 4.1 million in 2020. Its expansion, however, has brought about a sharp decline in vegetation, turning the city into a collection of urban heat islands.

A recent study says that Yaoundé will get hotter over the next five years. Yaoundé’s urban heat island phenomenon is magnified by the fact that poverty in the city is high, leaving many residents without the means to cool their homes. This has resulted in health problems, ranging from headaches and fatigue to breathing difficulties. Geographer Philippes Mbevo Fendoung sets out what’s needed to cool Yaoundé down: more green spaces, fewer hard surfaces, new reflective buildings, public ponds and fountains, fans for residents, new shady areas and affordable air conditioning.

What are urban heat islands?

Urban heat islands are areas in cities where the temperature is higher than in the surrounding rural areas. This is mainly due to reduced green spaces. Surfaces such as concrete and asphalt absorb and retain heat rather than reflecting sunlight back into the atmosphere.

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Urban heat islands are a problem for public health. People living there suffer more heat-related illnesses. Those with respiratory problems get sicker, and the heat has negative effects on mental health. This all gets worse during heatwaves and the environment becomes generally uncomfortable.

In Yaoundé, over the past ten years, the forest area around the city has halved, making the city even hotter.

What kind of heat problems is Yaoundé experiencing?

The temperature in the city is rising rapidly, and the densest areas have become heat islands that grow in size as more people move to Yaoundé from rural areas.

We worked this out by using satellite images, zoomed in to 10 metres, that we processed in open source geographic software to map city and green areas. This helped us see temperature differences over time, and spot the parts of the city most affected by urban heat islands. We noticed that hard surfaces in Yaoundé (such as pavements and parking lots) had increased by six times since 2015.

We then used a formula to forecast future surface temperatures in Yaoundé. We applied the average rate at which temperatures are rising to the current temperature, with a small margin of error to account for natural changes or uncertainties in the data. This way, we found that temperatures of 24-31°C in 2015 are likely to reach 38°C by 2030.

There are a number of reasons for this:

Buildings heat up the city: Concrete buildings and asphalt roads absorb and retain the sun’s heat, releasing it at night, blocking the city from cooling down.

Concrete jungle environment: Trees and plants play an essential role in regulating local temperature through evapotranspiration. Their absence makes the heat island even hotter and less pleasant.

Air pollution: With an increasing number of vehicles on the road in Yaoundé, exhaust emissions are rising. Fine particles and exhaust fumes increase local temperatures and cause respiratory and cardiovascular disease, especially in hot weather.

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Climate change has arrived in Yaoundé: Rising temperatures and more frequent extreme weather events (such as droughts and heavy rains) are making Yaoundé even hotter.

Badly designed buildings that can’t cool down: Many buildings in Yaoundé, particularly in working-class neighbourhoods, are poorly designed. Without air conditioning or adequate ventilation, indoor temperatures can become unbearable.

The city needs water it doesn’t have: The hotter Yaoundé gets, the more demand there is for water. But the city has frequent water cuts and the water is sometimes undrinkable. Not having enough clean water to drink or to water crops makes the heat’s impact worse and puts food supplies at risk.

Yaoundé can’t keep up with its growing population: Rapid urbanisation has meant unregulated growth, not enough services for everyone, poor waste management, and environmental degradation. Because the growth of the city is not planned, it is difficult to set up green spaces.

How are Yaoundé’s people experiencing the rise in temperatures?

We surveyed 300 households in Yaoundé and found that only 2.9% had airconditioning. Not all households had fans. About 45.5% of families in Yaoundé earn very little – between US$89 and US$177 per month. Even though that’s slightly more than the national monthly minimum wage of US$70, it’s far too little to afford an airconditioner, which costs roughly US$339.

Most (91%) of the households we surveyed told us that the heat caused more heat strokes and breathing problems like asthma. Children and older people suffered most. They were all suffering from stress and anxiety.

We also surveyed farmers who said that because of the heat, their crops were not growing well. These farmers were already not well off, and the heat meant lower incomes and less food to eat. They had to buy expensive irrigation equipment and heat-resistant crop varieties, which reduced their profits even more.

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Workers in the informal economy said being exposed to the heat without adequate protection caused them fatigue and illness, limiting their ability to work.

Public transport was uncomfortable on hot days and people stayed at home, reducing the income of small traders who depend on the movement of customers.

Our research found that low-income communities and disadvantaged areas were hardest hit by the urban heat island. The hotter Yaoundé gets, the worse inequalities will become as impoverished people will have less access to cooling infrastructure and healthcare.

What needs to happen next?

Existing buildings: New adaptive zoning regulations are needed to compel developers to adapt their buildings to climate change.

New buildings: Yaoundé urgently needs more green spaces, such as parks and tree-lined areas. These have to be a compulsory part of all new building and housing developments.

Informal settlements: An estimated 60% of the population of Cameroon live in urban informal settlements with unpaved roads, homemade houses and a lack of drinking water and sanitation. These residents need training in how to build using rammed earth to make their homes more durable and cooler. Rainwater harvesting and ecological sanitation systems, like dry toilets that don’t use water, could be incorporated.

Informal settlement residents could also learn to design green roofs and pergolas for shade.

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Public awareness campaigns about heat effects must be launched. The city also needs to track public health during heatwaves and improve treatment for heat-related illnesses.

To get this done, government agencies, non-governmental organisations, and local communities will need to come up with climate adaptation plans together. Green bonds, urban resilience funds, public-private partnerships, eco-taxes and microfinance are urgently needed to pay for these sustainable development projects.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Philippes Mbevo Fendoung, Centre national de la recherche scientifique (CNRS)

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Philippes Mbevo Fendoung does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.