What are the challenges of and solutions to the expansion of Sub-Saharan cities, like here in Accra (Ghana)?

© jozuadouglas/Pixabay

The Challenges of the Sub-Saharan Urban Explosion


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Updated 10.05.2021

Sub-Saharan African cities are presently growing at a size and speed unprecedented in human history. This region of the continent, which was always very rural up to now, is becoming predominantly urban. Small, medium-sized and large cities are doubling in size year on year, with some growing by 1,000 inhabitants a day. UN-Habitat, the United Nations programme working towards a better urban future, held a General Assembly from 27 to 30 May 2019 in Nairobi (Kenya). Discover how scientists are working together to determine the political, structural and health challenges of this urban explosion, together with the profound social changes generated by the pervasiveness of city life.

Kinshasa spans some 40 km with no adequate public transport system.

© MONUSCO/Abel Kavanagh

La quadrature des infrastructures

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Roads, running water, sanitation, waste collection, electricity and digital networks, community facilities and services, the infrastructures simply cannot keep pace with the sustained rate of growth experienced by Sub-Saharan cities. “The dynamics of investments in infrastructures have varied in space and time, now reaching unparalleled levels in many of the continent’s cities”, explains geographer Olivier Ninot. “However, they are not enough to make a significant improvement to the quality of life of most city dwellers”.

The new toll motorway linking Dakar to Mbour also serves the new city of Diamniadio and the new Blaise Diagne International Airport.

© S. Baffi/Codatu

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Glaring shortcomings

From constant congestion and horrendous traffic jams at commuting times to rolling blackouts, frequent power outages and no waste management, the crippling effects of inadequate public infrastructures affecting African cities are manifold. Kinshasa, for instance, spans over 40 km east to west, but its public transport system is completely inadequate. Its 12 million inhabitants have to contend with erratic bus services, shared taxis, private cars and walking, all on roads that are mostly unpaved, unlit at night and which quickly become a quagmire with the first downpour. Moreover, despite being inferior in quality, the cost of the services across the whole continent is significantly higher than elsewhere. Urban households spend 10% or more of their budget on transport in several African villages like Lagos (Nigeria), Dar es Salaam (Tanzania), Abidjan (Côte d’Ivoire) and Nairobi (Kenya). Furthermore, between 2006 and 2016, almost 80% of Sub-Saharan African businesses suffered several power outages a month, yet the actual average cost per kilowatt hour (kWh) is around four times higher than the world average. Research performed by the Pôle de recherche pour l'organisation et la diffusion de l'information géographique [Research Centre for the Organisation and Distribution of Geographic Information] (PRODIG) shows that this lack of infrastructures is also a stranglehold likely to restrict the continent’s burgeoning digital development (1)

This latent lag in the deployment of urban infrastructures is a result of both increasing needs associated with the urban explosion, and long-standing insufficient investment.

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Investments in progress

 “Several reports indicate that the infrastructure deficit remains very highInvestment needs are as high as 100 billion dollars a year for the whole of the continent, including 25 billion for the cities’ infrastructures”, explains Olivier Ninot. “60-80% of the needs have been covered in recent years, which is an exceptionally high level, yet it remains inadequate given their scale.” This situation has fluctuated considerably over time, however. After several decades of major budget constraints between the 1980s and 2000s, marked by chronic under-investment, the continent saw a revival with the economic growth of the 2010s. The public authorities, which are the primary investors, covering 40% of the need, regained their investment capacity, reviving with the confidence and extravagance of international donors like the World Bank and the Agence Française de Développement [French Development Agency] (AFD). At the same time, the emergence of new investors like China, India, the Arab Emirates and private operators, has completely upturned the hierarchy of the African countries’ financial partners. While these new investors are willing to finance sizeable investments in many areas, their arrival is also expediting the formation of public-private partnerships, which often involve complex systems in terms of financing, construction and operations.

Renovation works on Dakar's historic railway to convert it to a Trans-European Railway and serve the new city of Diamniadio some thirty kilometres away.

© S. Baffi/Codatu

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Mega projects, major disparities

This new momentum brings with it countless projects aimed at connecting the districts to the water, electricity, sanitation and telephone networks and equipping them with basic infrastructures, as well as larger projects to create new infrastructures or develop the existing infrastructure, largely in the area of transport, specifically airports in Dakar (Senegal), Lomé (Togo) and Addis-Ababa (Ethiopia), urban trains in Dakar and Abidjan, bus routes with dedicated bus lanes for better traffic circulation in Lagos, Accra (Ghana) and Dar es Salaam, and ports in Lomé, Accra and Conakry (Guinea). IRD researchers have been studying how these larger projects are being devised and received. They have shown the ambitions of the infrastructure projects undertaken in the decade under the power of President Abdoulaye Wade in Senegal, and the city dwellers’ perspective on their usefulness, their scale, and their cost (2). Proof of the debate aroused by these sizeable investments, the modern road networks and interchanges constructed are largely perceived as being “for the benefit of the rich”.

The construction effort also involves controversial new city projects which have experienced mixed success. Backed by the capitals, they respond to the need for housing and reduced congestion (by devolving administrative or university functions, for example) as well as to the economic and technological ambitions of the larger cities and States. Following on from Kilamba in Angola and Vision City in Rwanda, Diamniadio (Senegal) is currently under development. The Sèmè City project (Benin) has been announced for 2030, while Ghana's Hope City project seems to have been abandoned.

Yet as significant as they are, these investments are largely focused on the big cities, to the detriment of their small and medium-sized counterparts which have, nevertheless, been absorbing the bulk of urban growth since the 1990s. “Offsetting these disparities between millionaire megacities and secondary cities is one of the challenges faced in the development of urban infrastructures in the future”, concludes the geographer.

© Martin Lozivit

Geolocation of a business in the Ladji district by the youth involved in the MAP & JERRY initiative, using mobile app OsmAnd.

Participatory mapping in Ladji-Cotonou

Thanks to the work of its residents, an informal district of Cotonou now features on the city's official maps(1). This formalisation of Ladji on the map is the result of a participatory science initiative supported by the IRD. The project, named MAP & JERRY, consists in widening access to digital technologies for young inhabitants who live remotely from them, while giving their district global visibility. It also attempted to identify the problems associated with uncontrolled waste disposal in this impoverished area of the city to alert the authorities and prompt them to take action.

Carried out with the assistance of the OpenStreetMap Benin community team and Benin’s first FabLab, BloLab, the project taught around forty young boys and girls how to assemble computers from recycled parts. They were then able to digitise the buildings and streets, before ground locating the area's key features like schools, clinics and landfills using smartphones. Lastly, they detailed the toponymy of the places on the final map.

For this marginal population of Benin's economic capital, this revelation of their district is an initial step towards recognition of their right to the city. The business could emulate this activity in other impoverished districts of African cities, areas that accommodate the majority of the continent's city dwellers.

Note :
1. Armelle Choplin & Martin Lozivit, Mettre un quartier sur la carte : Cartographie participative et innovation numérique à Cotonou (Bénin), Cybergeo : European Journal of Geography, 02 mai 2019

Contact : Armelle ChoplinUMR PRODIG


Notes : 
1. Olivier Ninot, Elisabeth Peyroux. Révolution numérique et développement en Afrique : une trajectoire singulière, Questions internationales, La Documentation française, 2018.

2. Jérôme Lombard, Benjamin Steck, Sidy Cissokho. Les transports sénégalais: ancrages internationaux et dérives locales. Sénégal (2000-2012) : les institutions et politiques publiques à l’épreuve d’une gouvernance libérale, CRES; Karthala, p.643-671, 2013.

Contact : Olivier Ninot - UMR PRODIG


In the cities, and here at the Cotonou market (Benin), the women’s work is intensive.

© Stéphane Brabant

An urban society in crisis

The development of city life in Sub-Saharan Africa has brought with it major social changes, including the emergence of a middle class, the impoverishment of the most disadvantaged, increased life expectancy, changes in marital practices and fertility, a rise in school enrolment numbers and women’s increased role in the market economy. “These changes, which affect the whole of African society to some degree, although the effects are exacerbated in the cities, are generating unprecedented changes in intergenerational relationships, gender relations and, more generally, lifestyles”, explains socio-demographer Agnès Adjamagbo. Three years of research carried out by the IRD's scientists in several African capitals paint a picture of these new city-induced social practices(1).

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Social relations under financial pressure

In contrast to the agricultural rural world that largely predominated up to now, city life has a substantial financial cost for its inhabitants that includes the increased price of staple foods, high total transport costs(2), higher expectations for the academic success of children resulting in the widespread use of private education and private tuition, increased rent and the soaring inflation of urban and peri-urban land. “The economic constraints are placing huge financial pressure on both heads of household and other adult members of the household”, points out anthropologist Anne Attané. “Sometimes, the children find themselves having to bear the brunt of these new expenses, either by being taken out of school or by having to do some form of street trading alongside their time at school, such as selling paper handkerchiefs, telephone cards or doughnuts”. This financial pressure, which causes even greater hardship to the most vulnerable social classes, generates a climate of tension within households. These conflicts are having a particular impact on conjugal relations(3), in some cases leading to marital breakups, as indicated by the high divorce rates in a capital like Dakar (Senegal).

The fear of poverty and hardship, which are real risks for a considerable segment of the urban population, is becoming increasingly pronounced in the way social relations are structured. Help from within families and communities, once part of the structure of West-Africa rural societies, is becoming increasingly elective, as the IRD's researchers have shown(4).

At odds with Sub-Saharan practices, low-cost rental accommodation in the urban outskirts often places several unrelated families in the same courtyard.

© Stéphane Brabant

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Residential and family changes 

Considered places of major social progress due to their supposed accessibility to basic services, in reality, the cities are struggling to keep their promises and the material conditions of urban life are having a significant impact on life choices and family structures. “The poorest populations are forced to leave the larger urban centres and settle in the suburbs where housing costs are more accessible”, explains Anne Attané. “The districts close to the city centre are now littered with popular rental housing which, in contrast to previous practices, places several unrelated family units in a type of ‘célibatorium’?where a number of individual houses are located around the same courtyard ”. The wealthy middle classes, meanwhile, have access to property in the new districts into which the conurbation extends, and most often opt for nuclear-type family models centred around a married couple and their offspring. The growing trend of unions without cohabitation and marital instability – magnified by the poverty and economic insecurity of households, which are driving men to go out seeking an income-generating activity – are also tending to trivialise situations of single parenting among women(5). In addition, much less perceptible changes are also emerging, such as non-formalised unions, reconfigurations of forms of polygamous marriage, male single-parenting, residential groupings of unrelated people, young people living with no ascendant at their side, and even isolated elderly people. And beyond these family models, this urban reconfiguration of society is bringing about changes to gender and generational relations.

In Cotonou (Benin), women traders walk the cities’ streets with goods on their head and children on their back.

© Stéphane Brabant

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An indispensable female economy

With the financial pressures, the spread of new family models and the closing gap in male and female levels of education, intrafamily roles are also being reshuffled”, observes Agnès Adjamagbo. Researchers have observed that traditional standards for sharing roles and responsibilities within families and couples are being challenged, and the model in which the man is the provider and the woman is the homemaker no longer holds(6). Women now carry out paid work to contribute to household expenses and, in some instances, supersede their husband if they are unemployed, earn too little to bear the costs alone or are simply absent. Indeed, 25% of urban households are now headed by women, many of whom are single parents(5). “The economic activities of women are prevalent in the streets, markets, small shops and pavements where a wide variety of open-air trade and services are carried out. The city economy is a female world of its own”, concludes Agnès Adjamagbo. 

Lastly, the expansion of urban life in Sub-Saharan Africa could have still further effects on the societies, specifically due to varying levels of breakdown in links with the village of origin and the weakening of the associated community solidarity. The attachment or detachment of second- or third-generation city dwellers to the rural world culture will galvanise the attention of tomorrow's scientists.


Notes :
1. Agence Nationale de la Recherche [French National Research Agency] (ANR) programme carried out between 2011 and 2015 in Ouagadougou, Cotonou and Lomé: Familles, Genre et Activités en Afrique de l'Ouest [Families, Gender and Activities in West Africa] (FAGEAC - ANR 10-SUDII-005-01).

2. With ever-longer urban travel distances owing to the urban sprawl and greater traffic density, the proportion of the household budget allocated to transport is getting higher and higher. Cf. A. Nikiema, E. Bonnet, et al. 2017. Les accidents de la route à Ouagadougou, un révélateur de la gestion urbaine [Road accidents in Ouagadougou, an urban management indicator], Lien social et politique, no. 78, pp. 89-111.

3. Attané, A. 2009 “Se marier à Ouahigouya : Argent et mutations des rapports sociaux de sexe, d’âge et de génération au Burkina Faso”. In Agnès Martial, La valeur des liens. Hommes, femmes et transactions familiales, Toulouse, Editions des Presses Universitaires du Mirail,  collection  Les anthropologiques, pp. 25-46.

4. Attané A.  et  R. Ouedraogo 2011. “Lutter au quotidien : effets de genre et de génération sur l’entraide intrafamiliale en contexte de VIH au Burkina Faso”. In Alice Desclaux, Philippe Msellati, & Khoudia Sow (éds.), Femmes et VIH dans les pays du Sud, Paris Editions de l’ANRS, pp. 207-216.

5.  Delaunay V., Adjamagbo A., Ouédraogo A., Attané A.et Ouédraogo S., 2018. La monoparentalité en Afrique : prévalence et déterminants.  Analyse comparative Bénin, Burkina Faso et Togo, in Anne E. Calvès, Fatou Binetou Dial et Richard Marcoux (éditeurs) Nouvelles dynamiques familiales en Afrique, Québec, Presses de l'Université du Québec, Coll. Les sociétés africaines en mutation,446 p.; doi : 10.2307/j.ctvggx3tg.10

6. Adjamagbo, A., Gastineau, B., & Kpadonou, N. (2016). Travail-famille: un défi pour les femmes à CotonouRecherches féministes29(2), 17-41; doi : 10.7202/1038719ar

ContactsAgnès AdjamagboAnne Attané - UMR LPED


An incantatory message, erected as an affirmation challenge by the local authorities in Sabalibougou in the outskirts of Bamako in 2015.

© IRD/Monique Bertrand

Urban governance: a complex equation

The growth of African cities broadly falls short of recognised standards in terms of economic attractiveness and urban planning. “At a time when multi-polar investment models?financed by public and private stakeholders and international funds, sustainable and inclusive development goals and international agendas are promoted by the United Nations and major development agencies, African officials are finding themselves torn”, explains geographer Monique Bertrand, specialist in urban governance. “To meet the donors’ expectations and yield to widely promoted neoliberal reforms, they must contend with contradictory demands and the complex reality of their cities’ expansion.” It is a delicate task and scientists are studying the manifold forms of this political performance(1).

The State is encouraging a property boom in the outskirts of the Bamako conurbation.

© IRD/Monique Bertrand

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Model city, actual cities

The economic development experience acquired by the larger conurbations of developed countries now enforces a model for the relocation of major industrial and tertiary functions to the metropolitan outskirts, and the creation of rapid communication channels to serve them. “This ‘model city’ blueprint applied to the cities that have emerged most recently, and are rapidly expanding, suggests promoting secondary centralities that will relay the historic economic centres, to revitalise the residential fabric and labour market in the new suburbs”, explains the specialist. This project investment model is proposed as an objective and a method to the African urban authorities. However, in reality, the expansion of Sub-Saharan cities is based largely on the unanticipated and non-regulatory progress of under-equipped districts, on a loose spatial expansion that is not conducive to economies of scale, and the dominance of informal employment. The rampant growth of the continent's conurbations therefore remains heavily dependent on the historic centres, which are themselves unequally rehabilitated. The public powers supposed to implement the model city are themselves undergoing construction.

In Bamako (Mali), a State decision aimed at aligning constructions at a certain distance from a newly constructed road forces owners to demolish part of their buildings.

© IRD/Monique Bertrand

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Laborious construction of the urban authorities

Up until the democratic transitions of the 1990s, the larger African cities had a centralised governance, often merging with technical ministries”, indicates the researcher. “The decentralisation efforts, particularly in West Africa, have redistributed to the existing urban governments or to new territorial authorities – often without any real resources – responsibilities that the States themselves were failing to fulfil. One of the effects of this ‘offloading’ has been the fragmentation of the cities’ management by driving municipal officials into greater competition for control over land resources.” Even before reflecting on strategic planning and coordinated efforts, these new local authorities have faced ongoing operating problems such as the renewal and maintenance of inadequate sanitation infrastructures, and the difficult recovery of municipal taxes, particularly from the markets where city dwellers continue to be bad payers.

Governance became even more complicated after the 2000s when these public authorities became multi-level and different regional bodies purported to coordinate or, on the contrary, restrict the municipal initiatives. The privatisation of public services and new requirements associated with the fight against poverty, in the name of the MDGs?millennium development goals determined by the United Nations, precursors to the sustainable development goals have, in fact, increased the number of contributors demanding a say in the cities’ management: private economic operators, from the very internationalised to the very small, multilateral, bilateral and decentralised partners, but also professional and civil society associations and community-based organisations at times supported by major international NGOs. Among this tide of often dissonant voices and ‘projects’ which sometimes overlap, local public stakeholders are struggling to be heard and to manage the actions. And their relations with the central public authorities – States, ministerial departments and devolved technical services – remain tense and distrustful, as demonstrated by the research work.

Ultimately, the coalitions of political, economic and social stakeholders expected to develop a forward-looking and sustainable city vision are struggling to emerge.

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Persistent obstacles

In addition to the governance bodies themselves, structural obstacles are also impeding the successful development of African cities. “Land control is a central challenge in urban planning, particularly if the goal is to have more compact and more energy-efficient cities”, points out the specialist, who is working on the land register problem in Bamako(2). Land ownership is far from being individualised and formalised throughout on a clear and consensual basis. The property markets and records of rights in the cities’ rural fringes are getting out of control, and the need for them to be regulated is growing among the recommendations made by the African cities’ international partners. “But this requirement overlooks the fact that these cities are perceived on their periphery as being responsible for an unfair monopolisation, as being real enemies of the agricultural communities; the planned safeguarding measures are still based only on land titles, they benefit the elite and stir up strong conflict which makes it difficult to implement urban projects”, concludes Monique Bertrand. In the researcher's opinion, scientists must strive to illuminate the political challenges these forced market changes raise.

© IRD/Bérénice BOn

A symbol of urbanisation at work, the new motorway between Nairobi and Thika is lined with shopping centres, housing projects and agricultural land.

Thika-Nairobi, the urban transition motorway

The landscapes often testify to the complexity of the territorial changes at work. The landscape along the sides of the motorway connecting the Kenyan capital to the city of Thika, situated some fifty kilometres away, aptly reflects the multiple interwoven dynamics around this completely new infrastructure. The first few kilometres upon leaving Nairobi reveal a succession of major projects, shopping centres and upmarket residential property, enlisting powerful private operators supported by international funds. A little further on, property development is carried out by smaller developers focused on rental accommodation for middle-income tenants in search of affordable housing. Then there are small plots of farmland, made vulnerable due to the scarcity of water resources, from which small and large investors alike hope to profit following a future value appreciation. This land, gradually eaten away by these investment or hoarding practices, contrasts with the large production areas located on the approach to the city of Thika, which benefit from large-scale irrigation projects.
The motorway therefore facilitates access to certain rural areas and allows agricultural goods to be transported, but it also speeds up the dynamics involved in converting farm land into housing projects, industrial parks and high-tech companies.

Note :
Jochen Monstadt, Rémi de Bercegol & Bérénice Bon, Translating the networked city : Urban Infrastructures in Nairobi and Dar Es Salaam, Routledge, Série “Studies in Urbanism and the City”, to be published (sept 2019)

Contact : Bérénice Bon - UMR CESSMA

The lack of sanitation provides an environment favourable to infections linked to drinking water quality and the proliferation of pests.

© IRD/Cristelle Duos

Crucial health challenges

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The lack of foresight in terms of infrastructures, the high population density, lifestyle changes, but also climate change – which is very significant in a tropical area – are posing a threat to the health of Sub-Saharan city dwellers. “Over 63% of the region's urbanites live in informal districts with no sanitation and are exposed to old-time infectious diseases like diarrhoea, typhoid and viral infections, linked to poor water quality or the proliferation of pests”, explains medical entomologist Florence Fournet. “But other worrying diseases are emerging in the cities, associated with modern life and the harmful effects it has on both the population and the environment. Moreover, contrary to popular belief, African city dwellers are in no better health than the rural population.” Within this context, the IRD's scientists are studying the multiple health problems linked to the accelerated urban growth of Sub-Saharan cities and the corresponding means of redress.

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Persistence of old-time diseases

The price paid due to the lack of health facilities in Sub-Saharan cities is high. With inadequate networks to distribute water and collect domestic wastewater, a large proportion of conurbations suffer high levels of infectious diseases associated with poor quality drinking water. The number of lives lost to diarrhoea, which has long been the leading cause of child mortality in the southern countries, remains high. “City dwellers often depend on handmade wells for their water supply”, explains the researcher. “In Bouaké in Côte d’Ivoire for instance, 80% of the population in certain districts obtain their water directly from groundwater. But as there is no sanitation, it is inevitably contaminated with human wastewater, with obvious health consequences.” 

And the urban sanitation infrastructures that do exist are often limited to a few rainwater collection channels where wastewater is often poured in by hand. Moreover, open defecation remains prevalent in many districts. This configuration, combined with the scarcity of household waste collection and treatment facilities, is favourable to the proliferation of rodents.

Sanitation is often limited to simple channels for evacuating rainwater, into which the populations dispose of their domestic wastewater and household waste.  

© IRD/Florence Fournet

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Above-ground rats

Rats can find room and board in abundance in Sub-Saharan cities”, explains biologist Gauthier Dobigny(1). “While they live a somewhat underground sewer existence in Western cities, here they live on the same level as humans. And this is true in districts with a high population density.” This overcrowding increases the risk of transmission of zoonotic diseases?infections whose agents are naturally transmitted from vertebrate animals to humans  like leptospirosis, typhoid and hantavirus, as revealed by the research carried out by the Unité mixte de recherche [joint research unit] (UMR) of the Centre de Biologie pour la Gestion des Populations [Biology Centre for Population Management] (CBGP) in West Africa(2). But it also increases the risk of epidemics of diseases that come from rodents which are then likely to be transmitted directly from human to human, such as Lassa fever and the plague. “In these urban conditions, the proliferation of rodents is difficult to control using traditional methods like predation and extermination”, the specialist points out. “Therefore, planning policies are essential if the city is to tackle the issue.” And the rats are not the only ones to have settled in the cities.

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City-dwelling mosquitoes

Contrary to all expectations, malaria is also on its way to becoming an urban disease. “Until recently, the Anopheles mosquito, the vector of the parasite responsible for malaria, could only reproduce in clean water, which kept the disease away from cities where the water is dirty”, explains Florence Fournet. But a few years ago, the insect adapted to the new conditions and began laying its eggs in polluted pools of water. The disease, mainly limited to rural areas, is now gaining ground in the cities.” And the anopheles is not the only mosquito enjoying itself in urban areas. Aedes aegypti, responsible for the yellow fever epidemics which devastated the West African capitals at the start of the 20th century, has already become habituated to this environment. Like its cousin Aedes albopictus, which finds breeding habitats conducive to its urban proliferation in plastic waste, old tyres or water pools, it now spreads (re-)emerging pathogens in Sub-Saharan cities, like the dengue virus. In addition to these exacerbated risks, new dangers are arising.

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Emergence of new diseases

Like the city dwellers of the North, Sub-Saharan city inhabitants are exposed to diseases associated with the modern consumerist lifestyle. Here, as in other cities across the world, access to more abundant food and diets that are higher in fat, sugar, animal proteins and salt has led to an explosion of so-called non-transmissible diseases like obesity, high blood pressure, diabetes and cancers. These consequences of changes in eating habits and the sedentary nature of city life are now affecting a variety of social classes, and not just the wealthy. They are now also prevalent in middle-income cities, as shown in a study conducted by the IRD's scientists in Bobo-Dioulasso in Burkina Faso(3). However, since cities are places where inequality is rife, far away from family agricultural resources which are lifesaving for the most impoverished, some residents also suffer from dietary deficiency and malnutrition. Impoverished city dwellers are also the main victims of a new epidemic: road accidents.

With road and public transport infrastructures unable to keep pace with the urban sprawl, traffic pollution and traffic accidents have soared in African cities.

© IRD/Florence Fournet

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Hazardous urban mobility

The continual expansion of Sub-Saharan conurbations has resulted in daily movements of millions of city dwellers in environments where public transport and road infrastructures are completely inadequate. These massive commuter flows have led to a dramatic increase in city traffic accidents, as shown by the IRD’s research work in Ouagadougou in Burkina Faso(4). In fact, traffic accidents have become the second leading cause of death for the poorest populations in the informal outlying districts of the region's capitals, which have undergone little if any road developments to cope with traffic levels. However, this is not the only consequence of this new urban mobility. “Every day, African city roads are bombarded with ever-increasing influxes of cars and two-wheeled vehicles, producing unprecedented pollution levels”, explains hydro-climatologist Arona Diedhiou(5)“Levels of fine particles are much higher than the WHO's standards in large Sub-Saharan cities. And complex mixtures are being produced between anthropogenic aerosols – produced by urban transport, constant combustion in open landfills, domestic fires, and grassland or forest fires – and natural aerosols, particularly desert dust transported from the Sahara.” Moreover, the WHO estimates that 90% of deaths linked to air pollution occur in Africa and Asia. The work carried out by teams affiliated with the IRD(6) aims to characterise the health impact of these emissions in West African urban areas as well as their seasonal fluctuations. The initial results obtained in Abidjan and Cotonou from the European project DACCIWA?Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa confirm the potential link between particulate pollution and respiratory diseases.

Floods, which are often deadly in the informal districts where building structures are precarious, are becoming more frequent in Sub-Saharan cities due to climate change.

© IRD/Florence Fournet

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In the eye of the climate

Lastly, Sub-Saharan cities are being hit with the very tangible effects of climate change full force. “For over a decade, the region has seen an unprecedented increase in extreme climatic events, as revealed by the IRD’s research” (7), explains the climate specialist. “Heavy rainfall is increasing and the conurbations with inadequate water infrastructures and built up soils regularly contend with major floods. They are both deadly, particularly in the poorer districts, and costly to the economy.” Furthermore, global warming, combined with a significant urban heat island effect?artificial micro-climate linked to the nature of the built environment, causing a rise in day and night temperatures  given the nature of urbanisation, makes life difficult for several months of the year in the Sahelian conurbations. This phenomenon inevitably leads to increased energy efforts which, in turn, play a part in increasing atmospheric pollution.

Lastly, all our work, whether on transmissible or non-transmissible diseases, on accidents, pollution or the effects of climate change in cities, point to a need to integrate health requirements into the design of urban policies”, explains Florence Fournet. “They also indicate the need to improve knowledge of urban social dynamics to involve city dwellers in the management of their environmentIn the future, our research will focus on ways to systematically incorporate health aspects into urban planning, but also to mobilise the cities’ inhabitants and society.” 

Notes :
1. Member of the expert panel for rodent-related issues recently set up by the WHO.

2. Gauthier Dobigny, Philippe Gauthier, Gualbert Houemenou, Armelle Choplin, Henri-Joël Dossou, et al.. Leptospirosis and Extensive Urbanization in West Africa: A Neglected and Underestimated Threat ?, Urban Science, MDPI, 2018.

3. Augustin Nawidimbasba Zeba, Marceline Téné Yaméogo, Somnoma Jean-Baptiste Tougouma, Daouda Kassié & Florence Fournet. Can Urbanization, Social and Spatial Disparities Help to Understand the Rise of Cardiometabolic Risk Factors in Bobo-Dioulasso? A Study in a Secondary City of Burkina Faso, West Africa. International Journal of Environemental Research and Public Health, 2017.

4. Aude Nikiema, Emmanuel Bonnet, Salifou Sidbega & Valery Ridde. Les accidents de la route à Ouagadougou, un révélateur de la gestion urbaine, Lien social et politique, n°78, pp. 89-111, 2017.http://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-08/010070760.pdf

5. Expert from the Intergovernmental Panel on Climate Change (IPCC).

6. Laboratoire de physique de l’atmosphère et de mécanique des fluides de l’Université Félix Houphouët Boigny (Abidjan, Côte d’Ivoire) et Laboratoire d’aérologie de la Faculté des sciences et techniques de l’Université d'Abomey-Calavi au Bénin.

7. Gérémy Panthou, Thierry Lebel, Théo Vischel, Guillaume Quantin, Y Sane, A Ba, O Ndiaye, A Diongue-Niang & M Diopkane. Rainfall intensification in tropical semi-arid regions: the Sahelian case, Environmental Research Letters, 30 mai 2018.

Contacts : Arona Diedhiou - UMR IGE / Gauthier Dobigny - UMR CBGP / Florence Fournet - UMR MIVEGEC