CITY SHAPES & CLIMATE CHANGE IN AFRICA
INDICATORS MEASURING URBAN COMPACTNESS
DIVERSITY OF AFRICAN URBAN FORMS
SWAC/OECD developed two indicators to compare the shape of Africa’s cities, by combining the Google AI Africa Open Buildings dataset and the urban agglomeration data from Africapolis. Using the co-ordinates and surfaces of 183 million buildings constructed in nearly 6 000 African cities, the indicators measure:
The built environment across cities varies according to location within a country as well as city size. Two trends have emerged. First, very large cities (above 4 million inhabitants) are more compact than large and intermediate ones. Second, sprawl and elongation increase with the city size up to 4 million people. This is because very large cities fill in the space between buildings and start to become more circular, reducing distances.
ELONGATED AND SPRAWLED CITIES
Africa’s cities are the most rapidly growing in the world. In 2020, 685 million people lived in urban areas. By 2050, urban dwellers are expected to reach 1.5 billion. More people will need more buildings, homes, schools, hospitals, markets and other services. Where and how these buildings and amenities are constructed matters, since these decisions will last for decades. Yet, African cities develop spontaneously with limited urban planning, resulting in a proliferation of precarious neighbourhoods, inadequate transport systems, congestion, rising outdoor air pollution and high living costs. Africa's cities are especially vulnerable to the effects of climate change. Flooding, heatwaves, landslides and extreme climate events mean that building resilient and sustainable urban spaces, and preserving ecosystems and biodiversity is critical.
THE SPACE BETWEEN BUILDINGS OR THE LEVEL OF “EMPTY” SPACE
THE EXTENT TO WHICH THE SHAPE OF THE CITY DEPARTS FROM BEING A CIRCLE
The most compact city has a round shape with short distances between buildings. The least compact has greater distances between buildings and more elongation.
FOR CITIES TO TAKE FULL ADVANTAGE OF THE OPPORTUNITIES OFFERED BY THEIR EXPANSION, THEY REQUIRE: Better, more accessible data on urban forms Analyses of the constraints and levers to sustainable urban development, a low-carbon future and stronger environmental and ecosystem services.
IMPLICATIONS FOR LESS COMPACT CITIES While many cities across the world grow upwards, becoming denser over time, African cities tend to grow outwards. This results in sprawl, which means that people travel longer distances to get to their destinations. Longer distances discourage active mobility such as walking and cycling, increase the cost of public transport, lead to higher energy demands and emissions of private vehicles as well as congestion. Longer distances also mean reduced access to services and opportunities. This presents the risk of locking in unsustainable transport modes such as private vehicles instead of low-carbon modes (walking, cycling or public transport). As a city’s population doubles, the energy demand for transport is expected to triple. This is because the average distance between buildings is predicted to increase by 45% and more people will have to travel longer distances.
SAHEL AND WEST AFRICA
Club Secretariat