Abstract
We use high resolution satellite data on the proportion of buildings in a 250x250 meter cell to study the evolution of human settlement in Ghana over a 40 year period. We find a strong increase in built-up area over time, mostly concentrated in the vicinity of roads, and also directly on the coast. We find strong evidence of agglomeration effects both in the static sense-buildup in one cell predicts buildup in a nearby cell-and in a dynamic sense-buildup in a cell predicts buildup in that cell later on and an increase in buildup in nearby cells. These effects are strongest over a 3 to 15 Km radius, which corresponds to a natural hinterland for a population without mechanized transportation. We find no evidence that human settlements are spaced more or less equally either over the landscape or along roads. This suggests that arable land is not yet fully utilized, allowing rural settlements to be separated by areas of un-farmed land. By fitting a transition matrix to the data, we predict a sharp increase in the proportion of the country that is densely built-up by the middle and the end of the century, but no increase in the proportion of partially built-up locations.
Highlights
The world population has been growing rapidly
If partially built-up areas grow disproportionately over time—e.g., because of haphazard growth of urban areas or agricultural intensification—this creates different needs for public infrastructure investment and market development than if population growth concentrates in a few high density areas. It would dictate a different spatial and size distribution of bank branches and retail outlets. We address this gap in the literature by examining the evolution of human settlements over the entire geographical space, focusing on partially buildup areas
We focus on Ghana, a West African country that has experienced steady growth in population and GDP, without incurring any civil conflict since independence in 1957
Summary
The world population has been growing rapidly. This is true in Africa where the population has multiplied manifold since the beginning of the 20th century, and is predicted to reach 4.3 billion by the end of the 21st [1]. Vollset et al make lower predictions overall, but still predict a large population increase in Africa during the first half of the century [2]. Increases in the African population have spurred urbanization in general, and the emergence of mega-cities of several million inhabitants in many—if not most—African countries [3, 4]. Though housing conditions in much of Africa improved considerably between 2000 and 2015, more than half of Africa’s urban population live in settlements with poor housing condition [5]
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