Africapolis: Measuring Urbanisation Dynamics in West Africa
Sahel and West Africa Club (SWAC) Secretariat
Africa is the least urbanised continent in the world but an urban transition is very much underway. This is particularly visible in West Africa where the number of urban agglomerations increased from 152 in 1950 to almost 2000 in 2010. Between 2000 and 2010 alone, the urban population grew by over 40 million people, making towns and cities home to 41% of the region’s total population.
Cities and their inhabitants are increasingly at the centre of development processes in African countries. However, there is still little data on the actual size of West African cities, their number, location, the distances between them, where and how they form and grow.
Such information is essential for designing and implementing a wide range of development policies at the local, national, and regional level, such as urban and land planning, public service provision, infrastructure and investment strategies, decentralisation and spatial development, as well as energy and climate change. This is where Africapolis, the study of West African urban agglomerations, comes into play. Africapolis is the regional programme of the e-Geopolis project which provides comparable and comprehensive measurement of worldwide urbanisation. The Africapolis programme is split into three phases: Africapolis I (West Africa, 2008), Africapolis II (East and Central Africa, 2011) and Africapolis III (Southern Africa).
What is urban?
The Africapolis study applies a simple framework to a complex issue: measuring urbanisation. Determining the size of an urban population, the level of urbanisation or the number of urban agglomerations all depend on the chosen definition of “urban”. However, the definition of urban in West Africa, like elsewhere, varies from country to country. For example, in Guinea-Bissau, a country of fewer than 2 million inhabitants, an agglomeration with a population of 1 500 is considered urban. In Nigeria on the other hand, which is the most populous country on the African continent, the lower numerical threshold for defining urban begins at 20 000 inhabitants. And in other cases, such as in Chad, the administrative status of an agglomeration determines whether it is urban or not.
Africapolis sorts through these differences by applying a simple definition of urban agglomerations that is consistent, irrespective of national definitions. Africapolis uses two criteria to define what an urban agglomeration is. First, an agglomeration must be a continuously built-up and developed area, with less than 200 metres between two buildings. Secondly, an agglomeration is considered urban if it has a minimum of 10 000 agglomerated inhabitants.
A distinctive methodology
Defining what urban means is very useful when dealing with varying systems of measurement. Yet the fact that a country’s population increases, or that its level of urbanisation doubles, does not provide any information on the spatial redistribution that accompanies these population dynamics, such as the geographic distribution of towns, their size, their number, or the distances between them – all information which is crucial for researchers, governments and development partners to make informed analyses on the design and impact of national policies and to plan for future trends.
Africapolis addresses these concerns by applying a unique methodology to improve the geo-statistical knowledge of West African urbanisation dynamics. By combining demographic sources with satellite and aerial imagery and other cartographic sources, Africapolis can pinpoint population estimates at the level of individual agglomerations. This morphological approach helps identify the territorial transformation processes that are currently taking place in the region and which, with a few exceptions, remain little explained and poorly measured. The methodology breaks down the urbanisation dynamics of the region into several levels of agglomeration including metropolises, secondary cities, the merging of villages and the formation of conurbations (defined as one continuous agglomeration formed by the merging of at least two initially distinct urban agglomerations).
Africapolis, the 2015 Update: More and bigger cities… but not too big
While densification of the West African urban network is clearly occurring and expanding (the region counts 22 metropolises today with over one million inhabitants, as compared to 10 in 2000), “megacities” remain modest in size (compare the size of Lagos to Shanghai, for example). Secondary agglomerations (population 100 000 to 1 million) tend to be understated in national urban networks. The under representation of these medium sized cities is further emphasised by the existence of an important number of small agglomerations between 10 000 and 100 000 inhabitants.
A major contribution of the Africapolis study is the identification of cities with fewer than 100 000 inhabitants. In contrast, most databases, including that of the United Nations, only identify cities of more than 100 000 inhabitants. The 2015 Africapolis Update provides population estimates for 2 965 identified agglomerations in West Africa, of which 1 947 have more than 10 000 inhabitants. This is vital demographic information because 90% of cities in the region had fewer than 100 000 inhabitants in 2010, representing a combined population of 45 million people.
Nigeria: Unique in Africa
Nigeria is the most populated country on the African continent and its economy dwarfs that of its immediate neighbours which are eight to seventeen times less populated. Half of West Africa’s population lives in Nigeria and the country’s urban characteristics are exceptional, accounting for half of the identified urban agglomerations and 10 of the 20 largest cities. However, the country’s demographic and urbanisation dynamics are particularly difficult to measure given the size of its population and the controversies which surround official data. Coupled with geographic and administrative sub-divisions that are specific to the country and its history, it has been difficult until now to estimate the population of Nigeria’s urban agglomerations.
Applying the Africapolis methodology, the 2015 Update provides a comprehensive analysis of population dynamics in Nigeria, including new urbanisation measurements, making it the most complete dataset on urbanisation dynamics in this country to date.
Africapolis makes it possible to map, understand and measure the dynamics throughout West Africa and compare the results to other regions on the continent and globally. The method is recognised by the international scientific community, is comparable, independent of national definitions and verifiable. Data inconsistencies and geographic and historical gaps in census coverage are a reality and remain a constraint in analysing urbanisation dynamics in the region; however Africapolis is a significant step towards closing the data gap.