Mapping an entire subcontinent for sustainable development

(Press-News.org) Using the first complete dataset of more than 415 million buildings across 50 countries in sub-Saharan Africa, researchers at the University of Chicago created an unprecedented approach to urban development, down to each street block.

The new analysis, published this week in Nature, pinpoints where rapidly developing nations lack “last mile” infrastructure and access to public services. It uses high-resolution data to measure street access to each building across the subcontinent, showing how connectivity to infrastructure influences traditional measures of development, such as basic water and sanitation services or educational and economic opportunities.

“When you look at developed cities you see something universal: Every building has street access, no matter if your city is a grid like Chicago or curvy like Rome. These connections give people access to water, sanitation, and garbage disposal, and an address to register for school or where the fire department can find them in an emergency,” said Luis Bettencourt, PhD, a Professor of Ecology and Evolution at UChicago who led the study.

But rapidly growing cities can struggle to build necessary infrastructure, especially in informal settlements, or slums. “These disconnections lead to a range of problems for residents, holding back their development and that of their cities,” Bettencourt said. “This paper shows how we can measure and then begin to address those deficits for each household in every building, anywhere in the world.”

Localizing development, block by block

The United Nations estimates that 1.12 billion people worldwide live in informal settlements that lack basic services. In 2015, the UN made poverty reduction and slum eradication one of its Sustainable Development Goals, a global blueprint for improving health and education, reducing inequality, and spurring economic growth.

The sheer scale of the problem makes it nearly impossible to know where to begin. One approach has been “localization,” or acting at the neighborhood level where development is tied to identifiable places and households. Using data for every building and street, Bettencourt and his co-author Nicholas Marchio, a Research Data Scientist at the Urban Science Lab at UChicago, show that localization is possible down to the block level.

They combined the first complete census of buildings in sub-Saharan Africa (created by digital mapping company Ecopia), street network data from OpenStreetMap, and population and demographic data from other sources to build the Million Neighborhoods Africa map. This interactive map lets you drill into individual blocks to see estimates of infrastructure access for each building, population statistics, and the total number of buildings vs land. This provides a new perspective on every city and town in the subcontinent, from Lagos to Johannesburg to Nairobi and everywhere in between.

Bettencourt and Marchio calculated every building’s access level as the length of the shortest path to any street boundary. The maximum number of buildings you have to pass to get to the street from the block’s least accessible building is its block complexity. This number, called the k complexity, represents how difficult it is to provide street access to each of the block’s buildings.

A formal, well-planned city block would have a low k value of one or two; higher values like three or four mean the block is less accessible with long access roads. The average block complexity across sub-Saharan Africa is eight.

“This research provides the first comprehensive dataset of population and development indicators for all street blocks in sub-Saharan Africa, alongside open-source tools to extend the data globally in a standardized and comparable manner,” Marchio said.

“For countries that lack timely and reliable spatial data at the neighborhood level—which is essential for everything from service delivery to basic demography—this research fills a critical gap.”

Urban science and development

The researchers also looked at the connection between block complexity and human development. They compared the variation in 67 different social and economic factors—including education and literacy, maternal and child health, housing quality, and crowding within dwellings—to block complexity, and saw that the more disconnected a neighborhood was, the worse off its residents were on every measure of well-being.

In some cases, the lack of services might be obvious, as in large, unplanned, “peri-urban” informal settlements at the edges of cities or in rural areas. The analysis shows that cities provide better access to infrastructure and higher measures of development than these areas. Yet the map also shows many smaller pockets of high complexity hidden within otherwise more developed areas. Improving access helps those areas too, not just by supplying physical needs like water or sanitation, but also by weaving them into social and economic fabric of the city.

The data paints a nuanced picture of how neighborhoods grow organically. “Developing cities have a lot of challenges to face, especially striving for greater prosperity and quality of life in the face of climate change. What is different now is that we can use advances in urban science and amazing new data to accelerate sustainable development,” Bettencourt said.

“In this way, we can learn something profound about how all cities develop. What makes a good city? And how do we create more effective and organic solutions to problems of development that preserve culture, preserve people's dignity, and preserve the history of each place?”

The study, “Infrastructure deficits and informal settlements in sub-Saharan Africa,” was partially supported by the Mansueto Institute for Urban Innovation and the Susan and Richard Kiphart Center for Global Health and Social Development at UChicago.

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