West African Cities Research Articles

Projected Changes in Rainfall Extremes over West African Cities Under Specific Global Warming Levels Using CORDEX and NEX-GDDP Datasets

We analyze long-term extreme events in daily precipitation for the period of 1950–2005 and future projections from 2006 to 2100 based on representative concentration pathways (RCP8.5) over West Africa, including twelve major cities of the subregion. The study uses two datasets from the Coordinated Regional Downscaling Experiments (CORDEX) and NASA Earth eXchange Global Daily Downscaled Projections (NEX–GDDP), for their potential to simulate extreme rainfall characteristics over West Africa. CORDEX datasets are dynamically downscaled from 9 General Circulation Model (GCM) and the NEX-GDDP is statistically downscaled from 21 GCM simulations from CMIP5. The ensemble members of each dataset were used for the analysis and evaluated with eight observations. The projected changes in the rainfall indices were analyzed at four Global Warming Levels (GWLs) under the RCP8.5 climate-forcing scenario. The projections from the CORDEX and NEX-GDDP ensembles were compared. Self-Organizing Map (SOM) analysis was used to classify the projected changes from the simulations into twelve groups, based on their characteristics. Both CORDEX and NEX-GDDP models perform well in simulating the frequency and intensities of daily rainfall characteristics for important parts of the domain. However, substantial differences exist between the models and their relative performance varies with the indices. In all cases, NEX-GDDP outperforms CORDEX in stimulating the extreme indices. On the projections, CORDEX showed a wider spread than the NEX–GDDP for RTOT and vice versa for R97.5pTOT for all the GWLs.

Socio-Economic, Health and Ecological Sustainability of Vegetable Supplies in West African Cities: Assessment of Stakeholders’ Knowledge, Attitudes and Practices in Accra and Greater Lomé

In West Africa, vegetable supply chain development projects in Accra and Greater Lomé focus scarcely on the knowledge, attitudes and practices (KAP) of vegetable producers, traders and processors. Thus, the research aims to assess the level of sanitary, socio-economic and environmental sustainability of vegetable production, trade and processing in these cities, based on the knowledge, attitudes and practices of stakeholders. A quantitative multi-criteria evaluation approach was adopted, with reference to Global Reporting Initiative (GRI) standard 13 and Codex Alimentarius (CXC 1-1969 then CXC 53-2003). A sample of 303 people (156 in Accra and 147 in Greater Lomé) was formed using purposive sampling based on the assertion of E.R. Babbie (2016) and L. Kish (1965) combined with the comparison of S. Sudman (1976). Kobocollect and MS Excel respectively served to collect data and calculate KAP scores and percentages. Arcgis and Google Earth facilitated geographic representation of the data. The results reveal low rates of ecological (27.2%), health (26.9%), socio-economic (39.9%), technological and innovative (18.6%) KAP, evaluated at 28.6%. These results are unfavorable to the achievement of the SDGs. Hence the importance of an integrated, ongoing eco-nutritional education program for all stakeholders.

Contrasting luxury effect on urban plant phylogenetic and taxonomic diversity in West African cities

ABSTRACT Urbanization is a driving factor for biodiversity loss and potential climate change by reducing carbon stocks. Understanding how urban development, as mitigated by socio-economic factors alters urban biodiversity is crucial for effective urban planning that maintains or improves environmental resilience. The luxury effect hypothesis predicts that wealthier parts of a city will have higher levels of biodiversity. This effect has been tested widely but we still have limited understanding of how wealth influences urban biodiversity in tropical regions of developing countries where plant species play profound sociocultural roles beyond aesthetics. This study investigates links between household income and the diversity of cultivated plants distribution within neighborhoods of two growing cities in Benin. We conducted a survey of 936 randomly selected households to record their socioeconomic characteristics and survey the cultivated plant species found in household gardens’. This enabled us to estimate household-level diversity metrics including taxonomic diversity and phylogenetic diversity. We found no global support for the luxury effect on phylogenetic diversity but rented properties had lower plant taxonomic diversity along with less phylogenetic diversity than privately owned houses. Taxonomic diversity is higher in the less urbanized areas while phylogenetic diversity is weakened. Household’s cultural connection to plants has a negative effect on both diversity indices. Our results highlight the complex relationships between socioeconomic traits and urban plant diversity distribution in two tropical African cities, which only partly confirmed the luxury effect hypothesis. Disentangling these complex relationships can help city planners and policymakers to take informed decisions to promote sustainable cities.

High-Resolution Modeling of Air Quality in Abidjan (Côte d’Ivoire) Using a New Urban-Scale Inventory

In West African cities, the impacts of the air quality on the health of the population is expected to increase significantly in the near future. For the first time to our knowledge, we conducted a high-resolution modeling study over Abidjan (Côte d’Ivoire) using the WRF-Chem model and the simplified GOCART model to simulate carbonaceous aerosols BC and OC, sulfate, dust, sea salt, PM2.5, and PM10. The simulations were carried out during January and February 2019, a period over which there are databases of observations available. The DACCIWA inventory provided anthropogenic emissions at the regional scale, whereas a new emission inventory has been developed for the city of Abidjan. In 2019, the emissions were 4986.8 Gg for BC, 14,731.4 Gg for OC, and 7751.6 Gg for SO2. Domestic fires were the primary OC source (7719.5 Gg), while road traffic was the largest BC emitter (2198.8 Gg). Our modeling results generally overestimate urban particle concentrations, despite having a better agreement for those based on the inventory of the city of Abidjan. Modeled concentrations of BC are higher in administrative centers due to road traffic, while OC concentrations are significant in densely populated neighborhoods.

Informal land markets and ethnic kinship in West African cities

We present an urban land use model with land tenure insecurity and information asymmetry regarding risks of contested land ownership, a very common issue in West African cities. A market failure emerges as sellers do not internalize the impact of their market participation decision on the average quality of traded plots, which in turn affects other sellers and buyers’ decisions. The equilibrium is suboptimal and has too many transactions of insecure plots and too few transactions of secure plots. This market failure can be addressed when agents trade along trusted kinship lines that discourage undisclosed sales of insecure plots. Such kinship matching is an important feature of West African societies, including on the market for informal land, as illustrated by a unique survey administered in Bamako, Mali. In the model, the extent to which the market failure is addressed increases with the intensity of kinship ties. When sellers also have the possibility of registering their property right in a cadastre, this not only further attenuates information asymmetry but also helps reduce risk. We find complementarity between kinship matching and registration: As transactions along trusted kinship lines tend to involve plots that are more secure on average, kinship matching makes registration better targeted at insecure plots traded outside kinship ties. In this context, a partial registration fee subsidy can bring the economy to the social optimum.11We are grateful to the editor and two anonymous referees for comments that helped us substantively improve the paper as well as to Amadou Cissé for the many discussions about social structures in West Africa that initially motivated this paper, to Demba Karagnara who coordinated field surveys in Bamako in 2012 and 2022, and to Pierre M. Picard, Jan Brueckner and Tony Yezer for suggestions and technical comments on the model. We are also grateful to Eliana la Ferrara and Karen Macours for useful insights on kinship and land markets in developing countries, as well as to Thierry Verdier, Miren Lafourcade and the participants to the Labor and Public Economics Seminar at the Paris School of Economics, to the International Conference of Development Economics and to the Annual Conference of the Centre for the Study of African Economies for various suggestions. We gratefully acknowledge the funding of the World Bank and of the Paris School of Economics Mobility Grant, a public grant overseen by the French National Research Agency (ANR-18-CE22-0013-01), the Labex OSE and the Labor and Public Economics Group at the Paris School of Economics .

Temporal variability and regional influences of PM2.5 in the West African cities of Abidjan (Côte d'Ivoire) and Accra (Ghana)

Study uses real-time monitors to analyze PM2.5 in Abidjan & Accra, revealing diurnal & seasonal patterns, highlighting city differences, & showing Saharan dust impact. Emphasizes RAMPs' efficacy & need for robust monitoring in West African cities.

Barriers and facilitators for food systems policy development and implementation in African countries and cities

Abstract Background The sustainable food systems policy index (SFS index) was created to evaluate government actions towards healthy diets from sustainable food systems at national and city level. A mapping of policies was conducted across East (Kenya, Tanzania, Uganda) and West (Burkina Faso, Benin, Ivory Coast, Senegal, Togo) African countries and cities. Only few recommended policies were in place. Therefore, this study set out to identify the barriers and facilitators for food systems policy development and implementation within food supply chains and environments at national and city level. Methods A total of 64 semi-structured interviews are being conducted (April-July 2023) across aforementioned eight East and West African countries. Per country, four city level and four national stakeholders actively engaged in the design, implementation or evaluation of food systems policies were selected, 36 working on food supply chains, 27 on food environments and one involved in both. Results Results of the interviews are expected to highlight common barriers and facilitators to develop and implement policies to obtain healthy diets from sustainable food systems. Moreover, these will contribute to the finalisation of the SFS index. Conclusions Understanding barriers and facilitators influencing sustainable food systems policies is key to achieving the sustainable development goals. Moreover, the final SFS index will be useable in countries and cities across the world to map existing policies to obtain healthy diets from sustainable food systems and identify areas of improvement.

5.C. Skills building seminar: Leveraging local government policies to improve food systems for public and planetary health

Abstract Changing food systems is one of the most promising and impactful ways to address nutrition and health, climate change and environmental degradation. The International Network for Food and Obesity/NCDs Research Monitoring and Action Support (INFORMAS) developed the Healthy Food Environment Policy Index (Food-EPI) to measure the extent of implementation of healthy food environment policies by governments compared to international best practice. The Food-EPI provides a mechanism to assess government policies and infrastructure support to create healthy food environments. The Food-EPI tool covers seven food policy areas, including composition, labelling, promotion, prices, provision, retail and trade, and six measures of infrastructure, including leadership, governance, funding, monitoring, platforms and health-in-all-policies. The Food-EPI process includes the drafting of a comprehensive evidence document on the implementation of policies, verified by government stakeholders and the assessment of those policies, as well as identification of priority policy actions by an expert panel at the national level. The tool and process were pilot tested and implemented in New Zealand in 2014 and then again in 2017 and 2020. Since 2014, about 50 countries have implemented Food-EPI at the national level, including more than 10 European countries. There is increasing demand for a similar monitoring tool and process which can be used at the municipal/city government level to assess government actions addressing food systems for both public and planetary health. Local governments can often make more rapid progress than national governments, but on the other hand may not have jurisdiction in all critical policy areas. INFORMAS recently developed a new Food Systems Policy Index, based on a compilation of international recommendations for good practice government policies to address food systems and a scoping review on the potential effectiveness of the recommended good practice policies and interventions to improve nutrition and environmental sustainability outcomes. The new index covers policies addressing food supply chains and food environments, and is being implemented in a range of West and East African and European countries and cities. The purpose of the workshop is to discuss the role and potential of local level government (cities and municipalities) policies in addressing food systems to improve both public and planetary. The workshop will have several key presentations, some with a more global perspective and some with a very practical local perspective. Together with the panelists and the audience, the key opportunities and challenges will be discussed for European cities and municipalities to address food systems, as well as the role of monitoring and benchmarking policy implementation to increase local actions on food systems. Key messages • Monitoring and benchmarking the policy implementation to address food systems to improve public and planetary health by governments is key to increase accountability for action. • A better understanding on the role and potential of local government policies in addressing food systems can be beneficial to accelerate and innovate policy implementation.

Telecoupled urban demand from West African cities causes social-ecological land use transformation in Saharan oases.

Little is known about the long-distance telecoupling effects of urban food demands on land use changes (LUCs) in remote oases of the Southern Sahara. Using the example of two typical oasis settlements on Mont Bagzam in the southern Aϊr Mountains of Niger which are linked to regional and global markets by an unpaved road since 2015, this study aimed at analyzing time trajectories of LUCs and related changing agricultural production patterns. LUCs were quantified for 1955 to 2022 using GIS-based mapping of agriculture and natural vegetation based on historical aerial photographs, CORONA and multi-spectral satellite images, and high resolution drone-based surveys. The results show a major increment in actively used agricultural land in the 850 ha watershed of the two oases from 11 ha in 1955 to 13 ha in 2003 and 68 ha in 2022 as well as the addition of 92 irrigation wells to 16 existing ones between 2003 and 2022. LUCs and evapotranspiration calculated from climatic data of a local weather station allowed to estimate changes of irrigation water needs in the selected watershed. While annual precipitation averages only 214 mm, local reference evapotranspiration may reach 1,476 mm year-1. Therefore, the additional annual irrigation water needs for the newly established fields between 2003 and 2022 cultivated to cash crops rose by 696 million l. To detect LUC effects on soil quality, soil samples of onion and garlic fields of different ages were collected employing a false-time-series approach. Results reveal increasing soil pH and salt concentrations and falling ground water tables, which reflects a negative water balance and ground water extraction above recharge levels. Our study provides evidence that the newly established telecoupled production systems on Mont Bagzam threaten the sustainability of existing local agricultural production and related livelihoods of agro-pastoralists.

A spatio-temporal dataset on food flows for four West African cities

Gaining insight into the food sourcing practices of cities is important to understand their resilience to climate change, economic crisis, as well as pandemics affecting food supply and security. To fill existing knowledge gaps in this area food flow data were collected in four West African cities - Bamako (Mali), Bamenda (Cameroon), Ouagadougou (Burkina Faso), and Tamale (Ghana). The data cover, depending on the city, road, rail, boat, and air traffic. Surveys were conducted for one week on average during the peak harvest, lean, and rainy seasons, resulting in a dataset of over 100,000 entries for 46 unprocessed food commodities. The data collected includes information on the key types of transportation used, quantity, source, and destination of the food flows. The data were used to delineate urban foodsheds and to identify city-specific factors constraining rural-urban linkages. The data can also be employed to inform academic and policy discussions on urban food system sustainability, to validate other datasets, and to plan humanitarian aid and food security interventions.

Source Apportionment of Ambient Particulate Matter (PM) in Two Western African Urban Sites (Dakar in Senegal and Bamako in Mali)

Following population growth and rapid urbanization, West African cities have become major sources of anthropogenic pollution. Additionally, Saharan dust has had a significant impact, representing a potentially toxic mix of sources for the population. This study characterizes the atmospheric composition and its sources in two African capitals, Bamako, Mali and Dakar, Senegal. TSP, PM10 and PM2.5 samples were collected during the dry season in 2009 when pollution levels were high: chemical analysis included organic carbon (OC), elemental carbon (EC), ions, and metals. PM2.5 and PM10 concentrations were 5–10 times and 3–8 times higher, respectively, than the 2005 WHO 24 h standards. Using PCA and PMF methodologies, five sources were identified in each city. In Bamako, traffic (motor vehicles and resuspended road dust) was the prevailing source of PM2.5 and PM10, accounting for 47% and 45%, respectively. Crustal dust was the second most important source (24–30%), followed by solid fuel combustion (16–13%) and secondary aerosols (10–16%). In Dakar, the following sources of PM2.5 and PM10 are identified: traffic (49%), mineral dust (16–25%), sea salts (15–20%) and industries (10–11%). Our study provides crucial information about the historical change in source characteristics in these two African cities, which can help for future mitigation strategies.

Heat wave monitoring over West African cities: uncertainties, characterization and recent trends

Abstract. Heat waves can be one of the most dangerous climatic hazards affecting the planet, having dramatic impacts on the health of humans and natural ecosystems as well as on anthropogenic activities, infrastructures and economy. Based on climatic conditions in West Africa, the urban centres of the region appear to be vulnerable to heat waves. The goals of this work are firstly to assess the potential uncertainties encountered in heat wave detection and secondly to analyse their recent trend in West Africa cities during the period 1993–2020. This is done using two state-of-the-art reanalysis products, namely the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) and Modern-Era Retrospective analysis for Research and Applications (MERRA), as well as two local station datasets, namely Dakar–Yoff in Senegal and Aéroport Félix Houphouët-Boigny, Abidjan, in Côte d'Ivoire. An estimate of station data from reanalyses is processed using an interpolation technique: the nearest neighbour to the station with a land sea mask ≥0.5. The interpolated temperatures from local stations in Dakar and Abidjan show slightly better correlation with ERA5 than with MERRA. Three types of uncertainty are discussed: the first type of uncertainty is related to the reanalyses themselves, the second is related to the sensitivity of heat wave frequency and duration to the threshold values used to monitor them, and the last one is linked to the choice of indicators and the methodology used to define heat waves. Three sorts of heat wave have been analysed, namely those occurring during daytime, nighttime, and both daytime and nighttime concomitantly. Four indicators have been used to analyse heat waves based on 2 m temperature, humidity, 10 m wind or a combination of these. We found that humidity plays an important role in nighttime events; concomitant events detected with wet-bulb temperature are more frequent and located over the northern Sahel. Strong and more persistent heat waves are found in the continental (CONT) region. For all indicators, we identified 6 years with a significantly higher frequency of events (1998, 2005, 2010, 2016, 2019 and 2020), possibly due to higher sea surface temperatures in the equatorial Atlantic Ocean corresponding to El Niño events for some years. A significant increase in the frequency, duration and intensity of heat waves in the cities has been observed during the last decade (2012–2020); this is thought to be a consequence of climate change acting on extreme events.

Evaluation of an early flood warning system in Bamako (Mali): Lessons learned from the flood of May 2019

AbstractDevastating floods have plagued many West African cities in the past decades. In an attempt to reduce flood damage in Bamako (Mali), an early warning system (EWS) demonstrator (Raincell App) was developed for flash floods. On 16 May 2019, while the demonstrator was partially operational, an intense rainfall event led to devastating floods. We carried out an experience feedback on this flood event by comparing EWS simulations to the results of a field survey. Given the synoptic situation and the rapid development pattern of the storm, none of the global forecasting systems were able to foresee its occurrence and magnitude. The hydrological model developed as part of the demonstrator correctly identified most of the locations where overbank flow occurred. In the absence of data, the predicted discharge and volume values could not be validated. However, they are realistic based on the water levels reported in the Post‐Disaster Needs Assessment report. It would be advisable to couple it to a two‐dimensional hydraulic model and add discharge and water level monitoring to the already existing rainfall surveillance scheme to further improve the system's performance. Increasing the local population's awareness of the dangers of clogged waterways is also mandatory.

Dating the origin and spread of specialization on human hosts in Aedes aegypti mosquitoes

The globally invasive mosquito subspecies Aedes aegypti aegypti is an effective vector of human arboviruses, in part because it specializes in biting humans and breeding in human habitats. Recent work suggests that specialization first arose as an adaptation to long, hot dry seasons in the West African Sahel, where Ae. aegypti relies on human-stored water for breeding. Here, we use whole-genome cross-coalescent analysis to date the emergence of human-specialist populationsand thus further probe the climate hypothesis. Importantly, we take advantage of the known migration of specialists out of Africa during the Atlantic Slave Trade to calibrate the coalescent clock and thus obtain a more precise estimate of the older evolutionary event than would otherwise be possible. We find that human-specialist mosquitoes diverged rapidly from ecological generalists approximately 5000 years ago, at the end of the African Humid Period-a time when the Sahara dried and water stored by humans became a uniquely stable, aquatic niche in the Sahel. We also use population genomic analyses to date a previously observed influx of human-specialist alleles into major West African cities. The characteristic length of tracts of human-specialist ancestry present on a generalist genetic background in Kumasi and Ouagadougou suggests the change in behavior occurred during rapid urbanization over the last 20-40 years. Taken together, we show that the timing and ecological context of two previously observed shifts towards human biting in Ae. aegypti differ; climate was likely the original driver, but urbanization has become increasingly important in recent decades.

Disclosure of HIV status and adherence to antiretroviral treatment in children and adolescents from Lomé and Abidjan

Introduction: in Africa, the proportion of minors with AIDS is ever increasing and adherence to treatment protocols is still suboptimal. The study investigated the conditions of HIV status disclosure and adherence to treatment in patients < 19 in two West African cities.

Impacts of COVID-19 Restrictions on Regional and Local Air Quality Across Selected West African Cities.

The emergence of COVID‐19 brought with it panic and a sense of urgency causing governments to impose strict restrictions on human activities and vehicular movements. With anthropogenic emissions, especially waste management (domestic and municipal), traffic, and industrial activities, said to be a significant contributor to ambient air pollution, this study assessed the impacts of the imposed restrictions on the concentrations and size distribution of atmospheric aerosols and concentration of gaseous pollutants over West African subregion and seven major COVID‐19 epicenters in the subregion. Satellite retrievals and reanalysis data sets were used to study the impact of the restrictions on Aerosol Optical Depth (AOD) and atmospheric concentrations NO2, SO2, CO, and O3. The anomalies were computed for 2020 relative to 2017–2019 (the reference years). In 2020 relative to the reference years, for area‐averaged AOD levels, there was a consequential mean percentage change between −6.7% ± 21.0% and 19.2% ± 27.9% in the epicenters and −10.1% ± 15.4% over the subregion. The levels of NO2 and SO2 also reduced substantially at the epicenters, especially during the periods when the restrictions were highly enforced. However, the atmospheric levels of CO and ozone increased slightly in 2020 compared to the reference years. This study shows that “a one cap fits all” policy cannot reduced the level of air pollutants and that traffic and industrial processes are not the predominant sources of CO in major cities in the subregion.

Food Flows and the Roles of Cities in West African Food Distribution Networks

In West Africa, rampant urbanization is changing food systems, including the magnitude and composition of food flows and the length of supply chains. An increasing body of literature discusses pathways to sustainable transformation of urban food systems taking into account links between urban and rural spaces. Research and policy have focused on the role of cities as consumption centers receiving food from local, regional, and global hinterlands. This study aims at widening the perspective on the role of cities in food distribution, by bringing into focus a city's function as a consumption, aggregation, and disaggregation center. The analysis is based on a comprehensive set of primary data on food flows collected in four West African cities across different seasons. The analysis shows that the investigated cities are integrated into multi-scale urban and market networks. Their position within these networks interacts with their reliance on other territories for food supply and with their functions, such as the aggregation of goods. The capital cities of Ouagadougou (Burkina Faso) and Bamako (Mali) relied more on lower-rank urban settlements further away, while Tamale, a secondary city in Ghana, acted as an assembly market for local rural producers and in turn supplied larger urban centers. Bamenda, a secondary city in Cameroon, acted as a consumption center sourcing mainly from its hinterland. Beyond that, city functions were context-specific and varied according to type of product and season. Extending the perspective on the role of cities has implications for policy, including bringing into focus and strengthening midstream segments, such as market and transport links.

Co-production of access and hybridisation of configurations: a socio-technical approach to urban electricity in Cotonou and Ibadan

ABSTRACT The article examines the dynamics of access to electricity in two West African cities: Cotonou (Benin) and Ibadan (Nigeria). Due to poor supply from the grid, households are developing varied ways of accessing electricity, based on different socio-technical dispositifs. In this paper we first demonstrate that access to electricity is based on co-production processes that must be approached from a multi-scale perspective (from the household to the urban scale). We then argue that particular attention to the socio-technical and spatial dimension of co-production arrangements makes it possible to interpret urban electrical configurations and their evolution. We thus show that co-production processes, relying on many actors and technologies to meet a growing and diversified demand for electricity in cities, support an ongoing movement of extension-hybridisation of electricity configurations on an urban scale, thus offering an interesting perspective on power changes in sub-Saharan Africa.

Impact of COVID‐19 on wild meat trade in Nigerian markets

Impact of <scp>COVID</scp>‐19 on wild meat trade in Nigerian markets

Crime and safety in urban public spaces: Experiences of Ghanaian women traders in the Makola market in Accra, Ghana

AbstractAlthough traditional markets and women traders in West African cities have long attracted the attention of scholars, limited studies exist on women’s experiences of crime and safety issues in this economic space that they dominate. This paper contributes to the growing geographical scholarship on gender and crime from the Ghanaian perspective as a result of the increasing urbanisation process that has raised concerns about crime and safety among urban dwellers. Using in‐depth interviews, the paper explores the experiences of three categories of Ghanaian women traders in a traditional urban market, Makola, in Accra, Ghana’s capital city. Theft cases appeared to be the most common criminal activity that women traders experience and this results in significant economic, social, psychological, and emotional effects on the lives of the women, with the most vulnerable being those who do not have enough resources to secure their livelihoods. We recommend that city authorities, the police, and other stakeholders support the efforts of these women traders through gender‐sensitive and equitable approaches to improve security in market spaces because market trade contributes significantly to city and national socio‐economic development.