Dar es Salaam Atlanta boundary overlay to depict urban area extend

Is it sprawl though?

Why the compact city might be an answer too short for urban development globally.

Preventing cities from sprawling and instead promoting medium to high densities has become a main feature of the urban policy debate, not only since it has been targeted on the highest level — with the United Nations making the prevention of sprawl a key goal for cities to follow in the New Urban Agenda in 2016. Commentators see fast-growing and, in their eyes, sprawling cities like Dar es Salaam and ask with doubt, “Are they ready to handle rapid urbanization with all this sprawl?”

And the suspicion towards sprawl comes for many good reasons. Sprawling cities are cities where more and more land (mostly residential) is developed further and further away from the city’s center(s) at low densities and inefficient land use. The global rise of sprawl over the last decades, measured in decreasingly connected street grids, has been impressively researched globally by Christopher Barrington-Leigh and Adam Millard-Ball¹ (check out this interactive map).

This trend has brought to the urban planet and its residents a lot of negative externalities. Sprawling development costs more per resident; these cities depend on car-centric living, which arguably makes people sick and unhappy;² and, of course, they are a major obstacle to combating climate change as all of the driving and energy consumption of large houses are a considerable part of urban CO₂ emissions.³ But is all sprawl the same?

Paris is usually portrayed as the European poster child for density. In publications, it is sometimes even portrayed as the opposite ideal to sprawl, here by UN-HABITAT:

Juxtaposition of the “compact city”, Paris, and the “Urban sprawl city”, Uberlandia, in a UN HABITAT Toolkit. From: UN HABITAT (2014): A new strategy of sustainable neighbourhood planning: five principles. Available at https://www.urbangateway.org/publicspace/document/new-strategy-sustainable-neighbourhood-planning-five-principles.

While Paris is extremely dense at the center, depending on the definition of sprawl you chose, it cannot be said that it has not “sprawled” in the past century. What we know about Paris is that regulations have, with a few exceptions, prohibited skyscrapers, while people moved outward as a larger demographic became richer and innovation in transport (car/rail) allowed it. The Atlas of Urban Expansion has produced great, tangible resources to investigate this development in many cities on the planet:

Paris’ urban expansion 1900–2014. Atlas of Urban Expansion 2016. Available at http://www.atlasofurbanexpansion.org/historical-data

Unlike some, I do not intend to jump to the defense of sprawl here, or negate the economic benefits of urban proximity.⁴ The issue I want to address is that there has emerged some kind of one-size-fits all compact-city paradigm⁵ that might not help us think about the “cities yet to come”. It is projected that urban built-up area in developing countries will have grown to 770,000 km² in 2030, from 300,000 km² in 2000.⁶

How does this anti-sprawl paradigm prescribe how we think of the urban development of cities in the Global South, particularly in Africa? In essence, it comes back to the age-old question of what we see as the ideal city. The debate about the “compact city”, a broad concept describing the ideal trajectory of a non-sprawling city, comes from planners and subsequently donors in North America and Europe where cities did develop in their own way. Going with Donald Brown from University College London, I say we have to be careful not to take a one-size-fits-all approach that originates in a particular Euro-American urban experience.

Like other advice from the sustainability debate (fossil fuel based energy consumption, or car-dependent cities), the compact city ideal is rooted in the advice to not repeat the mistakes of our past. However well-intentioned the call may be, the urbanizing societies of Africa and Latin America will have to consume land in their unprecedented rapid transition of mostly rural societies to more urban societies. In the sense of Shlomo Angel, Head of The Urban Expansion Program at NYU Stern, we should have to think about how to “make room for cities.” Of course we should encourage density — but if it doesn’t come around immediately, let’s encourage whatever space creation prevails.

As my colleagues and I have observed in Yaoundé⁷, and others in Bamako⁸ or Dar es Salaam⁹, in urban Africa, land on the urban fringes is developed quite liberally and informally, giving in to market pressure. In crowded cities, that makes a lot of sense. As an economist would say, wherever the utility of farming is higher than the utility of creating housing, there will lie the fringe of the city.¹⁰ With more demand for housing, this fringe moves further away. This is not to say that this informal development is without problems: the lack of enforcing planning regulations means that land might be used inefficiently, be badly serviced, and could create conflicts between former users and new owners, among other challenges. For example, it’s unfortunate when a homeowner who built last year finds out their neighbor down the block has cut off road access to their house.¹¹ Arguably, though the regimes that steer how peri-urban land is developed in many African cities today might have pitfalls, they also work: they develop land.¹²

Yet, the core of these problems does not lie in low density, but in institutions. The ideal would be to control this development to avoid high retrofitting costs later. Is it also feasible or even optimal to artificially constrain this development to avoid “sprawl”? To take a closer look at urban expansion in a booming African city, we turn to Dar es Salaam.

Downtown Dar es Salaam with an inland view. Photo: Julian Ruoff, rights reserved.

Many of Africa’s large coastal cities are what Todd Litman calls “unconstrained cities” in his piece on “optimal urban expansion.”¹³ These cities are surrounded by an abundant supply of lower-value land, geographically only bound by the coastline. For Dar es Salaam, it is no surprise that, while gaining tremendously in population, it has also grown in size quite a bit. Coming from a small port town, “Dar” covered roughly 855 km² of settled area in 2014¹⁴ while housing 4.8 million people (an estimated 6.7 million in 2020).¹⁵ This means the population density of Dar es Salaam’s built-up area is around 5,600 persons per km², and most likely higher today. This is a higher urban extent density than London, at 4,500 persons per km².¹⁶ As a longer trend, the population has grown in Dar es Salaam at an astonishing 5 to 6 percent per year. There is no reason to assume the spatial expansion can or should really be contained. Below, I visualized its spatial expansion since 1974:

Built-up area evolution of Dar es Salaam, 1975–2014 (1990 N/A). Boundaries are Dar es Salaam’s 3 administrative districts. Global Human Settlement Layer (2014). Own illustration.

In only 15 years, an almost empty field, 22 km away from the waterfront downtown but close to the major road that connects Dar es Salaam to the capital Dodoma, has become a neighborhood of its own (image below). Over the same period, older neighborhoods closer to the center, such as Kimanga, have densified.¹⁷

Urban conversion 22 km from Dar es Salaam city center: Aerial view of the same plot 2004 and 2019 between Kwembe and Msigani. Yellow colored house for reference. Google Earth.

In contrast, taking Atlanta which is also classified as “unconstrained expansion” (Litman), and is infamous for being “sprawling”, we see the stark difference in phenomena we call sprawl: While being home to an estimated 4.9 million inhabitants in 2014,¹⁸ the built-up extent of the area comprising Atlanta and its surrounding suburbs covers roughly 10,800 km²,¹⁹, more than 12 times the area of the Tanzanian economic capital and with about the same population at the time.

A Gif shows the urban extent of Atlanta in 1975, 1990, 2000, and 2014
Built-up area evolution of Atlanta and suburbs, 1975–2014. Boundaries are around 16 counties that host Atlanta and its suburbs. Global Human Settlement Layer (2014). Own illustration.

Notably, Atlanta is not a monocentric agglomeration. Not everyone commutes downtown but might work in a suburban center close by. Polycentrism has been discussed as potentially giving sprawl some form of efficiency.²⁰ Yet, scholars found that polycentric sprawl as observed in Atlanta has the lowest housing-to-job proximity and goes along with inefficient land uses.²¹ For our illustrative comparison to Dar es Salaam, 22 km from the historic center, land use seems rather wasteful.

Downtown Atlanta. Photo: Payton Chung (CC BY 2.0)
Select comparison to Dar es Salaam — suburban development 22 km away from Atlanta’s center in Sandy Springs, GA in 2019. West of major road more typical single family development, but multi-family development has been added along this major road in the past decade, east of the road. Google Earth.

Of course, comparing distances for such different cities is not that straightforward. Travel times are the currency of urban expansion, and while in our neighborhood in Dar es Salaam it would take roughly 1 hour to commute to downtown by car, it would take only 20 minutes for the same distance in Atlanta, taking advantage of the highway network. That being said, in Atlanta we can clearly see a different kind of sprawl, which is hard to compare to the “sprawl” in Dar es Salaam or other emerging urban areas.

For those who fear a sea of suburbia visible from space around the world and therefore overemphasize the compact city in places that need more space — don’t stress out. I would argue that this epitome of development is far from “natural.” That’s simply because the two major drivers of American sprawl that facilitated the infamous metro areas of Atlanta, Los Angeles, or Houston are not natural laws. They have been policy choices. For one, the Federal Aid Highway Act of 1956 heavily subsidized both fuel and the construction of highways for individualized, fast transport. Along with that came homeownership subsidies, primarily for single-family housing on large lots, and the de facto ruling out of denser development, with overly strict local zoning regulations that persist until today, which are unheard of in European countries.²²

But delving into the particularities of America’s suburbia, I rather want to speculate that:

  • Cities like Dar es Salaam, even if unconstrained by geography, are sprawling in a different, maybe new way, that yet has to be understood in depth. In other words, the metro areas of African cities might neither become Atlanta, nor Paris.
  • More likely, density in heavily populated cities like Dar es Salaam will go down as incomes rise,²³ but if policy allows for it, the decline will be reasonable. Artificially constraining density can hamper this, of course. Mumbai planners, post-independence, made the mistake of sticking to colonial zoning codes, which led to a large swath of low-rise housing stock in a mega-city.²⁴
  • To understand this expansion process, its impacts, and how we can guide it, we should look closer at the land conversion processes that are taking place at scale everywhere.

Therefore, we should acknowledge that Cities will most likely continue to sprawl — or should we just say “expand”? — but at higher densities than expected from US suburbia. To find out how to guide this expansion, we should make more efforts to understand it in detail before we doom it as “sprawl” and prescribe an inapplicable antidote.

Thank you for coming to my sprawl talk.

References and Notes

[Title image] The administrative footprints of Atlanta (plus suburbs) and Dar es Salaam (the 3 administrative districts) at scale.

[1] Barrington-Leigh, C. and Millard-Ball, A., 2020. Global trends toward urban street-network sprawl. Proceedings of the National Academy of Sciences, 117(4), pp.1941–1950.

[2] Speck, J., 2013. Walkable city: How downtown can save America, one step at a time. macmillan.

[3] Glaeser, E., 2011. Triumph of the City. Pan.

[4] C.f. Bruegmann, R., 2006. Sprawl: A compact history. University of Chicago press.

[5] Brown, D., 2017. Challenging the conceptual boundaries of the compact city paradigm in sub-Saharan Africa: Towards Southern alternatives. London: DPU Working Paper, (187).

[6] Angel, S., Parent, J., Civco, D.L., Blei, A. and Potere, D., 2011. The dimensions of global urban expansion: Estimates and projections for all countries, 2000–2050. Progress in Planning, 75(2), pp.53–107. Vancouver

[7] Pascal, T., Tchekoté, H., Mabou, P., Zelezeck Nguimatsa, S., Zaengerling, B., and Kolowa, T., 2020. Perspectives for Sustainable and Efficient Land-Use in a Large Expanding City: An Analysis of Residential Land Delivery Systems in the Yaoundé Metropolitan Region in Cameroon. Paper prepared for presentation at the World Bank Land and Poverty Conference 2020. The World Bank — Washington DC, March 16–20, 2020.

[8] Durand-Lasserve, A., Durand-Lasserve, M., and Selod, H., 2015. Land Delivery Systems in West African Cities: The Example of Bamako, Mali. Africa Development Forum series. Washington, DC: World Bank. doi: 10.1596/978–1–4648–0433–5 . License: Creative Commons Attribution CC BY 3.0 IGO https://openknowledge.worldbank.org/handle/10986/21613

[9] Schlimmer, S., 2019. Land transactions in the rural-urban fringes of Dar es Salaam and Nairobi: driving forces, stakeholders and challenges for land governance. Paper prepared for presentation at the “2019 World Bank Conference on Land and Poverty” The World Bank — Washington DC, March 25–29, 2019.

[10] Anas, A., Arnott, R. and Small, K.A., 1998. Urban spatial structure. Journal of economic literature, 36(3), pp.1426–1464.

[11] Tchékoté, H., Ngouanet, C., 2015. Périurbanisation anarchique et problématique de l’aménagement du territoire dans le périurbain de Yaoundé. In : Bogaert J. & Halleux J.-M., 2015. Territoires périurbains. Développement, enjeux et perspectives dans les pays du Sud. Gembloux, Belgium: Presses agronomiques de Gembloux.

[12] Picard, P.M., Selod, H., 2020. Customary Land Conversion and the Formation of the African City. Policy Research Working Paper; No. 9192. World Bank, Washington, DC.

[13] Litman, T., 2016, July. Determining optimal urban expansion, population and vehicle density, and housing types for rapidly growing cities. In Proceedings of the World Conference on Transport Research, Shanghai, China (pp. 10–15).

[14] Corbane, C., Florczyk, A., Pesaresi, M., Politis, P., Syrris, V., 2018. GHS built-up grid, derived from Landsat, multitemporal (1975–1990–2000–2014), R2018A. European Commission, Joint Research Centre (JRC).

[15] United Nations, Department of Economic and Social Affairs, Population Division, 2018. World Urbanization Prospects: The 2018 Revision, Online Edition.

[16] Dar es Salaam: my own calculation; London: The Atlas of Urban Expansion. Note that my methodology produced an estimate and differs from that of the Atlas of Urban Expansion.

[17] Abebe, F.K., 2011. Modelling informal settlement growth in Dar es Salaam, Tanzania. University of Twente Faculty of Geo-Information and Earth Observation (ITC).

[18] U.S. Census Bureau, Population Division.

[19] Atlanta and surrounding suburbs is defined as made up of these 16 counties: Bartow, Carroll, Cherokee, Clayton, Cobb, DeKalb, Douglas, Fayette, Fulton, Gwinnett, Hall, Henry, Newton, Rockdale, Spalding. The Atlanta-Sandy Springs-Alpharetta metro area defined by the census is even larger than that.

[20] For North America, see Lang, R., 2003. Edgeless cities: Exploring the elusive metropolis. Brookings Institution Press;
for Europe, see Davoudi, S., 2003. European briefing: polycentricity in European spatial planning: from an analytical tool to a normative agenda. European planning studies, 11(8), pp.979–999.

[21] Cutsinger, J. and Galster, G., 2006. There is no sprawl syndrome: A new typology of metropolitan land use patterns. Urban Geography, 27(3), pp.228–252.

[22] Hirt, S., 2010. To zone or not to zone? Comparing European and American Land-use Regulation. PNDonlineII.

[23] Angel, S., Parent, J., Civco, D.L. and Blei, A.M., 2011. Making room for a planet of cities.

[24] Glaeser, 2011.

Urban Development Consultant @WorldBank, wondering how to be smart about urban growth and disaster risk so cities work better for people.

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