Boulaq Al-Dakrour, one of the most densely populated districts of Egypt’s capital Cairo, is the hottest spot in the city during the summer months, according to an international study. The district was found to be 5 °C hotter than areas south of Qorsaya Island in the Nile.

The findings were the result of research by Arup, a global sustainable development consultancy, which conducted the study using artificial intelligence (AI) and satellite images. The study looked at hot spots in a 150 km2 sample of the urban centres of cities including London, Los Angeles, Madrid, Mumbai, and New York. It is based on data collected at the peak of a heat wave on 11 June 2022.

The heat is attributed to the fact that in Boulaq Al-Dakrour “100 per cent of the zone is built up” and “there is no vegetation or water in the area.”

Meanwhile, the cooler areas south of Qorsaya Island in the Nile enjoyed both greenery and water with “28 per cent of their surface covered in vegetation and 30 per cent covered in water,” according to the study.  

“The World Bank estimates that climate change will increase temperatures in Egypt by between 1.5 °C and 3 °C by mid-century. This will mean heat waves become more frequent, severe, and long, with an average of 40 additional days of extremely hot days per year projected,” the study said.

According to the study, the hottest spots of the cities surveyed had less than six per cent vegetation cover, while the coolest spots had over 70 per cent and were almost entirely in parks and away from residential areas.

“We’ve inadvertently designed many of our cities to be hot. We’ve pushed out nature and concreted our streets and built high buildings of steel and glass. We’ve largely confined our green spaces to parks away from where most people live,” said Dima Zogheib, the nature positive design lead at Arup.

Cities around the world are getting hotter due to climate change, with the number of cities exposed to extreme temperatures of 35 °C and above expected to triple by 2050.

“Ponds, lakes, trees, grasses, soils and other surfaces that allow water to permeate into the ground have to be seen as vital infrastructure that is essential to helping us adapt to climate change,” Zogheib said.

The heat is often at its worst at night, as according to the study building materials such as cement absorb heat during the day then slowly release it when the sun goes down. “This causes stress and health issues and acutely impacts vulnerable citizens including children and the elderly,” the study said.

Income inequality can also play a role in people’s ability to cool themselves, since poorer areas are less likely to have greenery and shade from trees to keep streets cool, the study said.

To tackle the problem, the authors suggest planting more trees to lower the temperatures in cities and reduce heat-related mortality.

While greening the city is important, biodiversity is also crucial. “It is as critical as load testing and structural safety checks on a bridge,” wrote Neil Harwood, a biodiversity and nature specialist at Arup, in the study.  

Deploying only one plant species or habitat typology leaves infrastructure vulnerable to pests, disease, and climate shocks, Harwood said.

For example, if there is space to put in five trees to shade a road, instead of five identical trees that require high levels of care and maintenance, it is important to choose trees of three to five different species.

While designers should use local species, they also need to consider forecasts of increasing heat, droughts, or extreme rainfall events and widen the pool of appropriate plant species to include ones that are resilient and can benefit local fauna species, the study said.

Permeable surfaces such as bare or planted soil also help absorb less heat compared to surfaces like concrete or asphalt, the study said. Increasing permeable surfaces and allowing water to infiltrate into the ground can cool the surrounding environment.

The study suggests using every available space to combat heat. Greening building facades and roofs or using white paint to change the reflectiveness of surfaces to reduce the amount of heat absorbed from the sun are all policies that should be implemented, it said.

It also recommends establishing cooling spaces in cities for people to take refuge in during heat waves. In Seoul in South Korea the Cheonggyecheon Stream has been brought back to the surface after being paved over in the 1950s to make way for a new road, for example.

“The new stream became a tourist attraction and a valued public space that the community flocks to during heat waves,” the report said. Bringing back drinking water fountains could also improve people’s health and become main access points for water during a drought, it added.

Changing the way people live in cities over the next decade is important in dealing with higher temperatures, the study said. For example, people should incorporate siestas, re-consider office hours, introduce shop and restaurant closures at times of peak heat, and encourage the growth of an evening economy.

* A version of this article appears in print in the 24 August, 2023 edition of Al-Ahram Weekly