In the rapidly urbanizing landscapes of sub-Saharan Africa, the interplay between infrastructure deficits and the proliferation of informal settlements poses one of the most pressing challenges of our time. Recent research spearheaded by Bettencourt and Marchio delves into the spatial intricacies of these phenomena, harnessing cutting-edge geospatial datasets to reveal unseen patterns and offer a novel framework for understanding urban complexity across this diverse and dynamic continent.
At the heart of this study is the use of extensive building footprint data generated from high-resolution satellite imagery provided by Maxar and meticulously processed through the DigitizeAfrica platform. This comprehensive mapping of building outlines forms the foundation for analyzing urban structure with unprecedented granularity. Complementing this are detailed street network datasets extracted from OpenStreetMap, carefully curated to exclude irregular pedestrian pathways, ensuring that the analysis captures functional urban environments critical for infrastructure access.
Population distribution, a crucial dimension in evaluating urban and peri-urban dynamics, was estimated using two authoritative raster-based datasets: LandScan and WorldPop. These datasets provide global population grids at resolutions fine enough to be meaningfully downscaled to street-block levels. The researchers employed a sophisticated allocation method that apportions population counts proportionally based on building area within delineated blocks, thereby aligning demographic data with the physical urban fabric, an approach that significantly enhances the precision of population density estimates.
The delineation of urban, peri-urban, and rural areas was grounded in geometries from the Global Human Settlement Layer (GHSL) Urban Centre Database, with peri-urban zones defined as 10-kilometer buffers around urban extents. This spatial stratification acknowledges the fluid and transitional nature of urban expansion in African contexts, recognizing peri-urban areas as critical arenas where infrastructure deficits often manifest most acutely.
A unique aspect of the study is the generation of spatial blocks—polygonal units defined by contiguous street networks supplemented by natural boundaries such as coastlines and rivers. These blocks serve as the basic analytical units, offering a lens through which the relationship between urban morphology and socio-economic indicators can be explored. The authors highlight the exclusion of footpaths and minor trails from this network to maintain focus on the infrastructure most relevant to formal urban accessibility.
To validate the richness and accuracy of the building footprint data, the team conducted cross-verifications with satellite imagery across various regions, taking into account the likelihood that very small structures may not be residential in nature. Additionally, the completeness of OpenStreetMap street networks was systematically assessed, reinforcing the reliability of the subsequent spatial analyses.
The research further integrates socio-demographic insights from the Demographic and Health Survey (DHS) program, encompassing 238 administrative regions within 22 countries, with 40 unique surveys conducted over a decade (2010-2021). This broad dataset provided nearly 370 subnational observations, enabling rigorous correlation analyses between the spatial block characteristics and indicators such as slum population proportions and health outcomes. Principal component analysis across 67 measured indicators distilled multidimensional data into actionable insights regarding informal settlement distribution and urban complexity.
One of the paper’s notable contributions is the validation of a metric denoted as k, an estimator designed to quantify informal settlement prevalence. This metric was rigorously calibrated against self-reported slum maps from nine urban areas, demonstrating its robustness in capturing the spatial footprint and heterogeneity of underserved urban locales. Such advancements in measurement are pivotal in addressing the long-standing opacity surrounding informal settlements, often excluded from official statistics.
Beyond the empirical findings, the study pioneers an open, interactive visualization platform accessible at millionneighborhoods.africa, which empowers users to explore multi-scale urban characteristics across the continent. This tool presents an intuitive interface allowing users to transition seamlessly from a continental overview to granular analyses at the street-block level. Features include dynamic displays of urban complexity k, building counts, population estimates, and land usage types, all overlaid with satellite imagery for real-time visual validation.
This visualization caters to a broad audience, ranging from urban planners and policymakers to researchers and civil society actors, fostering transparency and enabling data-driven decision-making. By situating population density estimates within tangible urban forms at high resolutions, the platform sheds light on the spatial distribution of infrastructure needs, potentially guiding targeted interventions in areas of acute deficit.
Importantly, the research underscores the significance of peri-urban zones as liminal spaces where informal settlements frequently expand amidst the absence of adequate infrastructure. These zones, often overlooked in traditional urban planning frameworks, emerge as critical targets for infrastructural investments that can alleviate poverty and improve living conditions, ensuring sustainable urban growth trajectories.
The integration of multisource datasets—building footprints, comprehensive street networks, population grids, and socio-demographic surveys—exemplifies a holistic approach to urban analysis, leveraging the strengths of remote sensing, crowd-sourced mapping, and institutional data repositories. This methodology offers a replicable model adaptable to other regions confronting similar urbanization and informality challenges globally.
This groundbreaking work not only advances scientific understanding of urbanization patterns in sub-Saharan Africa but also delivers practical tools and metrics to quantify and visualize the infrastructural deficits contributing to informal settlement formation. Its implications extend beyond academic discourse, charting pathways for responsive urban governance and inclusive policy frameworks vital for dealing with the continent’s explosive urban transformation.
As the global community increasingly recognizes the centrality of sustainable and equitable urbanization to development agendas, studies of this caliber illuminate the pathways through which data-driven insights can catalyze effective solutions. By bridging satellite-derived spatial data with ground-truth demographic and health indicators, Bettencourt and Marchio’s research sets a new standard for spatial urban analysis and underscores the urgency of addressing infrastructure deficits as a cornerstone to solving the informal settlement crisis in sub-Saharan Africa.
Subject of Research:
Infrastructure deficits and informal settlements in sub-Saharan Africa analyzed through high-resolution spatial data and demographic surveys.
Article Title:
Infrastructure deficits and informal settlements in sub-Saharan Africa
Article References:
Bettencourt, L.M.A., Marchio, N. Infrastructure deficits and informal settlements in sub-Saharan Africa.
Nature (2025). https://doi.org/10.1038/s41586-025-09465-2
Image Credits:
AI Generated
Tags: building footprint data analysisdata-driven urban planning solutionsDigitizeAfrica platform for mappinggeospatial analysis in urban planninginformal settlements in urban areasinfrastructure development in sub-Saharan AfricaMaxar satellite technology applicationspopulation distribution in citiessatellite imagery for urban mappingstreet network infrastructure assessmenturban complexity in sub-Saharan Africaurbanization challenges in Africa
