Is Declining Density Always Bad?

+ Brandon Fuller

Rapid urbanization in the developing world will bring with it declining urban densities. Yet declining densities needn’t mean unsustainable sprawl. To see why, consider the case of urban expansion in Accra, Ghana.

According to the authors of the Atlas of Urban Expansion (available online and in print), Accra’s population grew at a rate of 2.6 percent per year, from approximately 1.8 in 1985 to 2.7 million in 2000. Over the same period, Accra’s urban land cover expanded at a rate of 6.6 percent per year, from approximately 13,000 to 33,000 hectares. Because land cover expanded more quickly than population, the city’s built-up area density declined from roughly 140 persons per hectare to 82 persons per hectare.

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According to Solly Angel, two forces drove the de-densification of Accra: rising incomes and subdivision of tribal land on the urban fringe. Per capita income doubled in Ghana between 1984 and 2000, leading to higher demand for dwelling space, land, and cars (the use of which allowed families to locate further from the city center). The village chiefs in charge of tribal land on Accra’s periphery responded by subdividing their land, distributing selected plots to villagers and leasing the remaining land to outsiders. What’s more, the government’s proclivity for taking land without compensation gave the chiefs extra motivation to develop their land, lest they lose it altogether.

In OECD countries, talk of subdivision and expansion raises concerns about environmentally harmful sprawl — we see denser cities as better cities. Yet many cities in the developing world are far too dense,  struggling with problems such as overcrowding, lack of light and air, pollution, congestion, and unsanitary conditions. In this context, urban expansion may provide welcome relief while keeping land and housing affordable for rural-urban migrants.

If a density of 30 persons per hectare is needed to sustain a minimum level of regular public transport, then the average density of U.S. cities — 24 persons per hectare in 2000 — can reasonably be described as unsustainable along the public transport dimension. In this context, densification seems like an appropriate response (preferably by removing inefficient rules that keep people from moving to densely settled areas voluntarily).

With approximate density of 82 persons per hectare in 2000, density in Accra was a long way from unsustainable (note also that the rate of decrease in density tends to approach zero with time). The containment/densification approach is not of much use in the context rapidly urbanizing developing countries. There, the primary challenge involves managing the decline to tolerable densities that are consistent with regular public transport services and affordable housing.

Tile image by Jason Armstrong.

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