BOOK OF ABSTRACTS FROM WORKSHOP ON THE VULNERABILITY, ADAPTABILITY AND RESILIENCE OF COASTAL AREAS IN CENTRAL AND WEST AFRICA IN A CHANGING CLIMATE (WACA-VAR)

Book of Abstracts WORKSHOP ON THE VULNERABILITY, ADAPTABILITY AND RESILIENCE OF COASTAL AREAS IN CENTRAL AND WEST AFRICA IN A CHANGING CLIMATE (WACAVAR) 4ème EDITION From 30 September to 02 October 2025 At Grand Bassam, Côte d’Ivoire Contact: Rafael Almar, Directeur de Recherche, Institut de Recherche pour le Développement (IRD), France) [email protected] Allassane Ouattara, Professeur Titulaire, Université Nangui Abrogoua, Abidjan Côte d’Ivoire [email protected] Donatus Angnuureng, University of Cape Coast, Ghana ; [email protected] https://wacavar.net/ Table of Contents CONFERENCE ORGANIZATION .......................................................................... 4 Organizing Committee ................................................................................................... 5 TERMS OF REFERENCE (ToR) ............................................................................ 6 Context ........................................................................................................................ 6 Objectives of the Workshop ............................................................................................ 7 Structure of the workshop ....................................................................................... 7 Dissemination of Research Results .................................................................................. 7 PROGRAMME .................................................................................................... ix ABTRACTS ........................................................................................................ 15 Geomorphology of the Ivory Coast Continental Shelf : History and Perspectives ................ 16 Restoration of the Mangrove Forest Cover in Dabou, Ivory Coast ............................... 16 Adaptation of women in the fishing sector to climate change in Grand-Lahou, Ivory Coast .. 17 CONTRIBUTION OF REMOTE SENSING TO THE EVOLUTION OF COASTAL LACUSTRINE ENVIRONMENTS IN CÔTE D’IVOIRE: THE CASE OF LAKE HÉBÉ ... 18 AFRICAN STRATEGY AND ACTION PLAN (2022-2032) ON CLIMATE CHANGE AND RESILIENT DEVELOPMENT OF THE AFRICAN UNION ........................................... 18 Monitoring Coastal Vulnerability using Physical and Anthropic Parameters: The Case Study of Lahou Kpanda and Grand Bassam, Cote d’Ivoire (Gulf of Guinea) ............................... 19 Nature-Based Coastal Defence: A Model-Based Assessment of Mangrove Effectiveness ....... 20 Coastal Land Subsidence and Sea-Level Rise Impacts in Ghana’s Data-Sparse Volta Delta: A Case Study from the ENGULF Project ........................................................................... 21 Assessing land subsidence and the impact of relative sea-level rise along the GULF of Guinea – Insights from the ENGULF project ............................................................................. 22 A review of two major threats to Nigeria’s coastal population: land subsidence and sea-level change ....................................................................................................................... 23 Changement climatique et impacts en région côtière : quelles stratégies d’adaptation pour une meilleure résilience en Côte d’Ivoire ? ............................................................................ 24 Has plastic pollution reached our plates? A case study on Sardinella in Ivory Coast ............ 24 Vulnerability of the Ivorian-Ghanaian upwelling to climate change in the northern Gulf of Guinea ....................................................................................................................... 25 IS VEGETATION RESILIENCE AFTER HUMAN DISTURBANCE POSSIBLE: THE CASE OF AZAGNY NATIONAL PARK (SOUTH, COTE D'IVOIRE)? ............................ 26 From space to shore: enhancing coastal planning in West Africa using satellite technologies 27 MAPPING OF THE SENSITIVITY OF THE IVORY COAST TO EROSION AND MARINE SUBMERSION ........................................................................................................... 27 Modelling wind transport in dune systems:Case of Essaouira beach (Morocco) .................. 28 Morphosedimentary dynamics of the Langue de Barbarie based on the example of Gandiole beach, Senegal. ............................................................................................................ 29 40-Year Journey of S horelin e Chang es Alon g the Benin Coast Using Satel lite Data T hrough the CASSIE Tool ......................................................................................................... 29 Assessing the Impact of degradation on carbon Storage by Rhizophora racemosa in SouthEast Periphery of Azagny National Park (Côte d’Ivoire). ................................................. 30 Peasant knowledge and sustainable management of agricultural land in the West African coastal zone facing the challenges of climate change : the example of Lower Casamance (South-West Senegal) ................................................................................................... 31 FLOOD RISK MAPPING IN WEST AFRICAN ESTUARY ENVIRONMENTS: THE EXAMPLE OF THE CASAMANCE RIVER DELTA, SENEGAL .................................... 32 The Saytoukat Géej, a citizen network monitoring marine pollution in Senegal .................. 32 Will Douala’s Coastland sink faster than sea-level rise? Investigating coastal subsidence and relative sea-level rise until 2050. .................................................................................... 34 How relocation in the face of coastal risks shapes senses of place and well-being? The case of a coastal community in Saint-Louis, Senegal. .................................................................... 35 CONFERENCE ORGANIZATION Scientific Committee - ALMAR Rafael (French Institute of Research for Development, IRD) - CECCHI Philippe (French Institute of Research for Development, IRD, Côte d’Ivoire) - OUATTARA Allassane (Nangui Abrogoua University) - KOMENA Boniface (CIRES, Félix Houphouët-Boigny University) - ABESSOLO O. Gregoire (University of Ebolowa, Cameroon) - ANGNUURENG B. Donatus (University of Cape Coast, Ghana) - OLUSEGUN Dada (Federal University of Technology, Akure, Nigeria) - MORAN Pierre (French Research Institute for Development, IRD, Senegal) Organizing Committee - OUATTARA Allassane (Nangui Abrogoua University) - CECCHI Philippe (French Institute of Research for Development (IRD), Côte d’Ivoire) - KOMENA Boniface (CIRES, Félix Houphouët-Boigny University) TERMS OF REFERENCE (ToR) WORKSHOP ON THE VULNERABILITY, ADAPTABILITY AND RESILIENCE OF CENTRAL AND WEST AFRICAN COASTAL ZONES IN A CHANGING CLIMATE (WACA-VAR) 4TH EDITION From 30 September to 2 October 2025 Grand-Bassam, Côte d’Ivoire Context The coasts of Central and West Africa (CWA) are low-lying areas with rich and functional ecosystems that provide multiple services. However, population growth and economic activities—often in the form of unplanned urbanisation (building in high-risk zones, sand mining on beaches, etc.) and over-exploitation of natural resources (fishing, mangrove harvesting, etc.)—combined with climate change, are putting significant pressure on these coastal ecosystems. As a result, CWA coastal areas are experiencing an intensification of phenomena such as coastal erosion, flooding, sea-level rise and pollution, leading to loss of human life, damage to property and infrastructure, and degradation of critical ecosystems and their resources. Several major regional-scale studies have documented the increase in these risks, amplified by rapid urban population growth and the expansion of economic activities in a changing climate. Consequently, the capacity to anticipate, plan and strategically manage development in CWA coastal zones is crucial to prevent potential risks. To respond to the urgent need to protect the coastal zones of Central and West Africa from the combined impacts of climate change and human activities, the West African Coastal Areas (WACA) programme was initiated. This programme supports the creation of the West Africa Coastal Observatory (WARCO) and the West Africa Coastal Master Plan (SDLAO). WARCO was established in 2018 with a mandate to: (i) support, improve and promote scientific and technical knowledge; (ii) provide tools for understanding and managing coastal zones; and (iii) contribute to the establishment of an integrated and sustainable coastal policy. The SDLAO is responsible for identifying key issues affecting coastal zones and national coastal risks within a broad framework, with emphasis on inter-state solidarity and reciprocity in coastal management. It also identifies priority coastal problems and analyses how well existing governmental instruments address these issues. These programmes require reliable, up-to-date information that is shared and made available at different decision-making levels to improve the strategic quality of decisions relating to the development, occupation and conservation of CWA coastal zones. In continuity with WACA, the programme “West African Coastal Areas – mapping Vulnerability, Adaptability and Resilience in a changing climate” (WACA-VAR) was launched to conduct an integrated study and develop innovative management strategies for sustainable coasts in the face of climate change, human activities and economic growth. Unlike WACA, which focused only on West African coasts, WACA-VAR also includes the coasts of Central Africa. An International Research Network (IRN), supported by the Institut de Recherche pour le Développement (IRD), was created in December 2022 to achieve the objectives of WACAVAR. This network brings together six universities in six West and Central African countries, under the supervision of the French IRD: • University of Douala (Cameroon) • Université Cheikh Anta Diop (Senegal) • Université Nangui Abrogoua (Côte d’Ivoire) • University of Cape Coast (Ghana) • Institut de Recherches Halieutiques et Océanologiques du Bénin (Benin) • Federal University of Technology, Akure (Nigeria) This network aims to: (i) improve knowledge of the current and future vulnerabilities of West and Central African coasts; (ii) provide new data, information and tools useful to investors, local and regional stakeholders (including coastal communities); and (iii) strengthen the capacities of local and regional actors (including postgraduate students at MSc, PhD and Postdoc levels) by training current managers, future coastal experts in Central and West Africa, and young researchers. In addition, this research network coordinates the collection of data on the hydrodynamic and morphological characteristics of Central and West African coasts through field measurement campaigns, and the implementation and development of coastal video-camera observation systems. This 4th edition in Côte d’Ivoire follows three previous editions held successively in Senegal, Ghana and Cameroon. Objectives of the Workshop The workshop, to be held in Côte d’Ivoire from 30 September to 2 October 2025, has a dual objective: • To disseminate research results on issues related to the management, development and monitoring of coastal zones in Central and West Africa. • To implement activities of the WACA-VAR programme and the IRN research network. Structure of the workshop Dissemination of Research Results To disseminate research results related to the management and development of coastal zones in Central and West Africa, the workshop will take place from 30 September to 2 October 2025 in Grand-Bassam and will focus on the following themes: • Diversity of West African coasts • Governance and management of coastal zones • Tools and training for coastal observation and management The research findings will be presented in the form of oral presentations. Target audience: • University lecturers and researchers • Researchers • Decentralised local coastal authorities • Companies and firms operating in the coastal sector • Associations • NGOs • Students ix PROGRAMME 16 Geomorphology of the Ivory Coast Continental Shelf : History and Perspectives Sylvain MONDE Félix Houphouet-Boigny University, UFR-STRM, Department of Geosciences 22 B.P. 582 Abidjan 22 Ivory Coast E-mail: [email protected] Ella Gwladys ODJOHOU Félix Houphouet-Boigny University, UFR-STRM Department of Geosciences 22 B.P. 582 Abidjan 22 Ivory Coast ([email protected]) Abstract The history of geomorphological approaches to the Ivorian continental shelf begins in the 1960s with the first oceanographic missions conducted by the Oceanographic Research Center. These initial investigations enabled the mapping of major underwater structures through morphology, sedimentation, and geological features. From 1967 to 1973, L. Martin conducted in-depth studies of the Ivorian continental shelf. His work, based on sea missions, resulted in the publication of the first detailed sedimentological map of the continental shelf. Martin identified the main sediment types and geomorphological structures, such as sandstone bars and depressions. Beginning in 1982, the TRANSIVOIRE missions, led by Tastet JP and Aka K (Universities of Abidjan and Bordeaux I), extended investigations to the deep ocean. These missions led to a better understanding of sedimentary processes and ocean current dynamics on the continental shelf. The years 1995 and 2000 saw the implementation of the oceanographic missions BATHY and SEDICOT. This work, supervised by MONDE S (Cocody University), uses GPS, digital echo sounders, and acoustic remote sensing. MONDE, in partnership with the IRD and the CRO, produced the recent bathymetric map of the continental shelf. This tool, which updates the topography of the seabed from 0 to 120 meters deep, is crucial for laying submarine cables by mobile phone companies, exploiting marine resources, maritime navigation in treacherous areas, and demarcating maritime borders (Côte d’Ivoire – Ghana). The perspectives offered by the coastal geomorphology of Côte d’Ivoire can be broken down into several areas. These include the contribution of sonar and continuous seismic surveys (to create acoustic "photographs" of geological formations), the analysis of cored sediments to characterize eustatic seafloor conditions since the last glacial period, and environmental protection against human impact. The geomorphology of the Ivorian continental shelf has seen significant progress thanks to the contributions of researchers. The contribution of new technologies to future studies will improve the accuracy of geomorphological maps and the understanding of ongoing oceanogeological processes Restoration of the Mangrove Forest Cover in Dabou, Ivory Coast Ouattara Kpatouma Achille; E-mail : [email protected] 17 Abstract The RCFM Project, understood as "Restoration of Mangrove Forest Cover," is part of the Global Blue Transformation Strategy, incorporating the specificities of Ecosystem-Based Adaptation. Its aim is to establish nurseries, plant mangrove propagules to restore forest cover, and, upstream, conduct an assessment study to determine the level of mangrove degradation in Dabou. In synergy with all partners and stakeholders, an RCFM Project team will survey the lagoon frontage of the Dabou area to measure the area of destroyed mangroves along the entire shoreline. The assessment will yield results that will guide the RCFM commitment, while also allowing for an evaluation of the impacts of the project's implementation. The RCFM Project will initiate awareness campaigns in all the villages concerned and plans to establish village sections for mangrove restoration. The Restoration Field Schools, named SCEADCI and KPATOUMA, will facilitate the ownership and management of these sections, both for planting and land maintenance practices, and for the protection of the restored mangroves. The expected results from the project implementation are : - Assessment of the level of mangrove degradation - Awareness campaigns for communities and authorities - Establishment of propagule nurseries in villages - Implementation of village restoration committees - Practical training in field schools - Planting and bank maintenance operations - Participatory mangrove monitoring operations - Documentation of mangrove restoration experience Keywords : Restoration, Mangrove, Blue Transformation, Dabou, Côte d’Ivoire Adaptation of women in the fishing sector to climate change in Grand-Lahou, Ivory Coast Aboya Narcisse, [email protected] , Maitre de Conférences, département de Géographie, Université Félix Houphouët-Boigny de Cocody, Abidjan Agnero Jean-Bruce, [email protected], Doctorant, école doctorale, Université Félix Houphouët-Boigny de Cocody, Abidjan Abstract: Grand-Lahou is a department rich in oceanic and coastal biodiversity. This vast and rich natural environment comprises a strip of Atlantic coastline and lagoons that cross it from east to west, characterized by a great diversity of oceanic, brackish, and continental species. However, under the effects of climate change, biodiversity is eroding, resulting in damage to wetlands, mangroves, spawning grounds, and coastal fishing habitats, thus accelerating coastal erosion. Coastal populations, particularly women who depend on fisheries resources for their livelihoods, are proving more vulnerable. Climate factors constrain the development of fishing activities and disrupt the organizational systems of coastal fishing communities. This 18 contributes to food insecurity and reduces the incomes of social groups, especially women involved in post-harvest fishing activities. Indeed, these women are both the most vulnerable from a socio-economic perspective and the most exposed to the specific risks of climate change. Faced with this challenge, they have developed strategies to adapt to the effects of climate change. This study analyzes the adaptation strategies developed by women to combat the effects of climate change. Surveys were conducted with 204 women fishmongers, smokers, and traders. They were distributed across eight localities in the Grand-Lahou department. The study initially focused on the vulnerability of women in post-harvest fishing activities. Secondly, it described the adaptation strategies developed by the women and finally assessed the reliability and sustainability of these strategies in the face of climate change. The results of this research indicate that the effects of climate change have led to a depletion of fish stocks. Furthermore, the adaptation strategies developed by the women have limitations and are not effective, or even sustainable, in the face of climate change. Keywords: Grand-Lahou, coastal, climate change, vulnerability in fisheries, women's adaptation CONTRIBUTION OF REMOTE SENSING TO THE EVOLUTION OF COASTAL LACUSTRINE ENVIRONMENTS IN CÔTE D’IVOIRE: THE CASE OF LAKE HÉBÉ Andho Ella Gwladys ODJOHOU 1*, Charles Albéric AKA 2, Rokyatou SAMASSY 1Sylvain MONDE 1 1 Department of Geosciences, UFR STRM, Université Félix Houphouët Boigny, 22 BP 582 Abidjan 22 (Côte d’Ivoire) 2 Oceanography Research Center (CRO) * Corresponding Author: Ella ODJOHOU 22 BP 582 Abidjan 22 (Côte d’Ivoire), Cél : (225) 07 08 18 89 04, E-mail [email protected] Abstract: Remote sensing plays a key role in studying the evolution of coastal lacustrine environments in Côte d'Ivoire, particularly in the case of Lake Hébé. Using satellite images and geospatial analyses, it is possible to track the morphological and hydrological transformations of the lake over several decades. Research on similar environments has shown that remote sensing enables the mapping of variations in lake surface area, the identification of sedimentation or erosion processes, and the assessment of human impact. By utilizing multispectral data and supervised classification techniques, scientists can detect changes in land use and the dynamics of aquatic ecosystems. In the case of Lake Hébé, a diachronic approach based on Landsat imagery could reveal trends of regression or expansion of the water body, influenced by climatic and anthropogenic factors. These analyses are essential for the sustainable management of water resources and the preservation of lacustrine environments. Keywords: Remote sensing, Morphology, Satellite imagery, Lacustrine environment, Evolution, Surface dynamics, Coastal zone. AFRICAN STRATEGY AND ACTION PLAN (2022-2032) ON CLIMATE CHANGE AND RESILIENT DEVELOPMENT OF THE AFRICAN UNION ATSE Kambo Martial, Coordonnateur Général du Pan-African Think Do Réseau Africain des Jeunes Chercheurs (RAJeC), [email protected] ; [email protected], (+225)0759674320, Côte d’Ivoire 19 Abstract The Global Green Wall Strategy is considered a crucial element of the AU's Agenda 2063 and provides a point of convergence for the three Rio Conventions: the United Nations Convention to Combat Desertification (UNCCD), the United Nations Framework Convention on Climate Change (UNFCCC), and the United Nations Convention on Biological Diversity (CBD). The GGW Strategy aims to ensure its contribution as a flagship program of the Decade for Ecosystem Restoration and to achieve the key objectives of the United Nations Sustainable Development Goals (SDGs). Furthermore, the Strategy fully supports the AU Strategy on Climate Change and Resilient Development (2022), the AU Green Recovery Plan, and complements other flagship AU and AUDA-NEPAD programs, including the African Forest Landscape Restoration Initiative (AFR100), the Programme for Infrastructure Development in Africa (PIDA), and the African Continental Free Trade Area (AfCFTA), among others. Achieving Agenda 2063 for Africa is impossible without proactive, collective, continent-wide efforts to address the impacts and burdens of climate change, which are hindering our integration and development. There is ample scientific evidence—corroborated by the voices of diverse segments of our own communities—that Africa is bearing the brunt of the impacts of climate change, despite contributing less than 4 percent of global greenhouse gas emissions and its historical responsibility being negligible. Our economies are heavily reliant on climatesensitive sectors, which share significant similarities across the continent. The increasing frequency of climate-related emergencies and conflicts on the continent continues to divert our scarce resources, hindering our long-overdue economic development. Climate change is already having a significant impact on Africa. We are the continent most vulnerable to climate change. The African Union Strategy and Action Plan for Climate Change and Resilient Development is a vital instrument for supporting regional collaboration on climate change and more effective international partnerships. It provides a framework for joint action and clearly articulates our priorities. It will unlock Africa’s potential to build climate-resilient communities and economies, which are integral to the continental vision of an “integrated, prosperous and peaceful Africa, driven by its own citizens and representing a dynamic force on the international stage” (AU Agenda 2063). Keywords: Agenda 2063, carbon market, GGW Strategy, AfCFTA Monitoring Coastal Vulnerability using Physical and Anthropic Parameters: The Case Study of Lahou Kpanda and Grand Bassam, Cote d’Ivoire (Gulf of Guinea) Anoumou Rene Tano1*, Paul Nadi Dangui2, François-Xavier Bella Bouo1, Angora Aman3, and Celestin Hauhouot2 20 1Laboratory of Fundamental and Applied Physics, Nangui ABROGOUA University, Abidjan, Cote d’Ivoire 2Laboratory of images treatment and geomatics, Tropical geography Institute, Felix Houphouet Boigny University, Abidjan, Cote d’Ivoire Laboratory of Sciences of Matter, Environment and Solar Energy, Felix Houphouet Boigny University, Abidjan, Cote d’Ivoire [email protected] Abstract: The coastal area of Lahou Kpanda and Grand Bassam, Cote d’Ivoire (Gulf of Guinea) are vulnerable to physical and anthropogenic forcing. The Integrated Coastal Vulnerability Index (ICVI), combining the Coastal Vulnerability Index (CVI) and the SocioEconomic Vulnerability Index (SVI), is used to assess the spatial and temporal dynamics of vulnerability in Lahou Kpanda and Grand Bassam. The results show that the integrated vulnerability index for Grand Bassam is higher than that for Lahou Kpanda. This index increases faster in Grand Bassam than in Lahou Kpanda. That signifies that the Grand Bassam coastline is more exposed to physical forcing and anthropogenic pressure than Lahou Kpanda. The increasing trend in vulnerability is due to rising wave energy, accelerating sea level and the increasing of population density. An assessment of the area's vulnerability for the 2040 and 2050 timeframes indicates an increase in vulnerability. To reduce this vulnerability, adaptation measures such as covering the coastline with mangroves, installing wave power plants, beach nourishment and, in the extreme cases, relocating coastal population should be considered by coastal zone managers and users. This approach could be used to monitor the vulnerability of West African coastline to physical and anthropic forcing. KEY WORDS: Coastal evolution, integrated coastal vulnerability index, physical forcing, anthropic pressure. Nature-Based Coastal Defence: A Model-Based Assessment of Mangrove Effectiveness Philip-Neri Jayson-Quashigah a,b, Wei Chenb, Bughsin Djathb, Edem Mahuc, Kwasi Appeaning Addoc a Institute for Environment and Sanitation Studies, University of Ghana, Legon, Accra, Ghana b Institute of Coastal Systems-Analysis and Modeling, Helmholtz-Zentrum, Hereon, Max-Planck-Straße 1, 21502 Geesthacht, Germany c Department of Marine and Fisheries Sciences, University of Ghana, Legon, Accra, Ghana [email protected] Abstract: Coastal regions are increasingly vulnerable to hazards such as erosion and flooding, which threaten infrastructure, ecosystems, and human settlements. Traditional responses have relied heavily on grey infrastructure, such as seawalls and groynes, which, while effective in the short term, often incur high costs and lead to ecological degradation. In contrast, Naturebased Solutions (NbS), particularly mangrove ecosystems, offer a sustainable alternative by enhancing shoreline stability through wave attenuation and sediment retention. This study 21 presents a model-based evaluation of mangroves as a coastal defence mechanism. Using the 1D morphodynamic model XBeach, we simulated shoreline dynamics under various scenarios to assess the protective capacity of mangroves. The baseline model was calibrated and validated against observed coastal profiles, achieving a root mean square error (RMSE) of 0.75 m in predicting. Scenario-based simulations explored the influence of mature mangrove stands at varying densities, positioned both on the berm and within the intertidal zone, under current and projected sea level rise conditions. Results indicate a substantial reduction in erosion: from 28 m³ to 0.9 m³ (97% protection) under present conditions, and from 468 m³ to 2.6 m³ (99% protection) under a projected sea level rise of 0.233 m by 2040. Notably, high-density mangrove placement on the berm – a scenario considered more feasible for local implementation— achieved up to 53% and 97% erosion reduction under current and future conditions, respectively. These findings underscore the effectiveness of mangroves as dynamic, adaptive coastal defence systems. The modelling framework provides a valuable decision-support tool for optimising NbS strategies in vulnerable coastal zones, particularly in regions with limited empirical data. Coastal Land Subsidence and Sea-Level Rise Impacts in Ghana’s Data-Sparse Volta Delta: A Case Study from the ENGULF Project Selasi Yao Avornyoa, *, Philip S. J. Minderhoudb,c,d, Pietro Teatinie, Katharina Seegerf, Leon T. Hauserg, Marie-Noëlle Woillezh, Philip-Neri Jayson-Quashigahi, Kwasi Appeaning Addoa aDepartment of Marine and Fisheries Sciences, University of Ghana, Accra, Ghana bSoil Geography and Landscape Group, Wageningen University, Wageningen, the Netherlands cDepartment of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy dDepartment of Subsurface and Groundwater Systems, Deltares Research Institute, Utrecht, the Netherlands eDepartment of Civil, Environmental and Architectural Eng., University of Padova, Italy fInstitute of Geography, University of Cologne, Albertus-Magnus-Platz, 50923 Cologne, Germany gDepartment of Geography, University of Zurich, Switzerland hFrench Development Agency, Paris, France iInstitute for Environment and Sanitation Studies, University of Ghana, Accra, Ghana *Corresponding author: [email protected] Abstract: Deltas are highly valuable environmental systems, ensuring various livelihoods through their ecosystem services. However, human impact and climate change stressors are impacting deltas immensely. Consequently, many deltas, including Ghana’s Volta Delta, are facing increasing risks, especially as hazards are increasing in magnitude and impacting coastal livelihoods. To provide a better understanding of coastal hazards in the Volta Delta, this study assessed the Delta’s subsidence regime and its consequences for the potential impact of sealevel rise (SLR). Using the Interferometric Synthetic Aperture Radar (InSAR) technique and Global Navigation Satellite System (GNSS) surveys, vertical land motion (VLM) was documented. Interferograms of Sentinel-1 data from 2016 to 2020 indicated subsiding rates of up to -9.2 mm/yr. By combining local VLM information with recent SLR projections and elevation data, this study updates those projections and provides local assessments of potential Relative SLR (rSLR) impact. According to these locally improved scenarios, up to ~45 % of the Delta will fall below local sea level by 2100, of which close to 10 % is explained by the 22 integration of local VLM data alone. Depending on the climate change scenarios used, land subsidence will increase the deltaic area at risk by 4.31 % (96.27 km2) to 10.18 % (227.64 km2) and consequently exacerbate its exposure to coastal inundation. To avert the projections, the study recommends robust monitoring regimes; alternative freshwater sources to groundwater; reduced sediment trapping and river obstruction; and the need to stall ongoing oil and gas prospecting and subsequent extraction in the Voltain Basin. Assessing land subsidence and the impact of relative sea-level rise along the GULF of Guinea – Insights from the ENGULF project Katharina Seeger1,2,3*, Philip S.J. Minderhoud1,2,4, Pietro Teatini1, Manoochehr Shirzaei5, Selasi Y. Avornyo6, Roberta Bonì7, Kwasi Appeaning Addo6, Femi Emmanuel Ikuemonisan8, Marie-Noëlle Woillez9 1 Department of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy 2 Soil Geography and Landscape Group, Wageningen University and Research, Wageningen, The Netherlands 3 Institute of Geography, University of Cologne, Cologne, Germany 4 Department of Subsurface and Groundwater Systems, Deltares Research Institute, Utrecht, The Netherlands 5 Department of Geosciences, Virginia Tech, Blacksburg, United States 6 Department of Marine and Fisheries Sciences, University of Ghana, Accra, Ghana 7 University School for Advanced Studies Pavia, Italy 8 Department of Physics, Lagos State University of Education, Lagos, Nigeria 9 Agence Française de Développement, France * Corresponding author: [email protected] Sea-level rise and land subsidence pose significant threats to low-lying river deltas and coastal plains worldwide, increasing their exposure to flooding and permanent inundation. Coastal/deltaic land subsidence often occurs gradually and thus unremarkable, with comparably slow but long-term reaction towards triggers and impacts. Though outpacing rates of absolute sea-level rise in many coastal areas of the world, it is often not adequately considered as a hazard in coastal impact assessments. Along the densely populated lowlands of the Gulf of Guinea coast, so far little has been known about land subsidence, its spatio-temporal pattern and its impact in terms of relative sea-level rise, population and land-use assets at risk. The ENGULF project addresses these gaps by providing up-to-date quantifications of present coastal land subsidence from Interferometric Synthetic Aperture Radar (InSAR) measurements and integrating them into first, tentative assessments of potential future relative sea-level rise impact using latest available elevation data corrected to continuous local mean sea level. This contribution summarises the outcomes of various research activities at local to regional scale from local and international institutions, all united under the flag of ENGULF. It is the ultimate goal of ENGULF to raise awareness and establish a regional Community of Interest on coastal land subsidence in West Africa in which knowledge exchange and discussions help to avoid the land from severely sinking and influence policy decisions at all levels. 23 A review of two major threats to Nigeria’s coastal population: land subsidence and sea-level change Femi Emmanuel Ikuemonisan 1, Philip S.J. Minderhoud 2, Roberta Boni 3 Marie-Noëlle Woillez 4, Pietro Teatini 5 1-Department of Physics (Physical Science Education) Lagos State University of Education, Oto/Ijanikin, Lagos, Nigeria. 2-Soil Geography and Landscape Group, Wageningen University, The Netherlands. Department of Civil, Environmental and Architectural Engineering, University of Padova, Italy., Department of Subsurface and Groundwater Systems, Deltares Research Institute, The Netherlands 3 Department of Science, Technology and Society (STS), University School for Advanced Studies (IUSS) Pavia, Italy 4Agence Française de Développement, Paris, France. 5Department of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy. Email: [email protected] Abstract: Nigeria's coastal region, located along the Gulf of Guinea, is increasingly vulnerable to sea-level changes driven by climate change and anthropogenic factors. As one of the countries with the longest low-lying coastlines in the region, Nigeria faces significant risks from rising sea levels. In some coastal cities, this vulnerability is compounded by vertical land movement (land subsidence), which undermines coastal resilience. Despite numerous studies examining Nigeria’s susceptibility to sea-level rise, few have focused on the specific rates of subsidence in key coastal cities, and none have provided a comprehensive review of the combined effects of land subsidence and sea-level rise. This study seeks to bridge this gap by synthesizing the available literature on land subsidence and sea-level change along the Nigerian coastline and identifying existing knowledge gaps. Our findings reveal that, based on InSAR measurements, significant land subsidence is occurring in Lagos, Port Harcourt, and Warri, accompanied by local sea-level rise. However, the absence of active GNSS stations necessary to calibrate and validate InSAR measurements limits confidence in these findings and increases uncertainty. Additionally, there has been a notable lack of data on oil and groundwater withdrawals and piezometric trends over recent decades, which is essential for accurately quantifying the relationship between ground fluid extraction and land subsidence. Integrating recent sea-level change measurements with vertical land motion and piezometric data is crucial for improving our understanding of land subsidence in Nigeria and for projecting relative sealevel rise. It is imperative to distinguish between global processes such as sea-level rise, which are beyond the control of Nigerian authorities, and local processes like anthropogenic land subsidence, which can be mitigated. This study represents an initial step towards developing effective mitigation and adaptation strategies to address relative sea-level rise in Nigeria. By addressing these critical knowledge gaps and differentiating between global and local processes, we can better inform policy and management efforts to increase the resilience of Nigeria's coastal regions. 24 Changement climatique et impacts en région côtière : quelles stratégies d’adaptation pour une meilleure résilience en Côte d’Ivoire ? Yaya SORO Pole pêche et Aquaculture, Université NANGUI ABROGOUA Abidjan, Côte d’Ivoire Email [email protected] Résumé :Le changement climatique engendre l’augmentation globale de la température dans l’atmosphère. Ces valeurs extrémales de température sont à l’origine de la fonte des calottes polaires. Ces volumes d’eau se retrouvent dans les océans après fusion, contribuant à l’augmentation du niveau de la mer. Les dénivellations ainsi occasionnées amplifient les érosions et submersions marines côtières. A ces impacts s’ajoutent le réchauffement des eaux de surface, l’augmentation de la fréquence et de l’intensité des évènements météorologiques extrêmes et l’acidification des océans. Face aux effets de ces changements globaux, les pays côtiers sont obligés de s’adapter. A cet effet, des données ont été collectés aux abords de quelques points chauds ‘‘Hotspots’’ en zone côtière de Côte d’Ivoire. Ces données sont en rapport avec l’exposition et la vulnérabilité qui, elle-même, est corrélée à la capacité d’adaptation et de sensibilité. Elles ont servi à cartographier l’exposition et la vulnérabilité, au regard des aléas érosion et submersion. Avec ces données, des projections climatiques basées sur le modèle climatique CMIP5 ont été faites, suivant les scénarios d’émission RCP4.5 et RCP 8.5, à l’horizon 2050. Les zones à risque ont ainsi été identifiées, ce qui permettrait de réduire l’ampleur des dégâts en cas de forte expression d’un aléa climatique en zone ivoirienne. Mots clés : zones côtières, changement climatique, érosion, submersion, température, Has plastic pollution reached our plates? A case study on Sardinella in Ivory Coast Fanta TOURE1,2, Ameline ORTS3, Olivier HEITZ4,Monique SIMIER5, Lassina DOUMBIA1, Allassane OUATTARA1, Philippe CECCHI2,6, Delphine BONNET3 1LEBA, Université Nangui Abrogoua, Abidjan, Côte d’Ivoire 2UMR Marine Biodiversity, Exploitation and Conservation (MARBEC), IRD, University of Montpellier, CNRS, Ifremer, Montpellier, 34095, France 3-UMR Marine Biodiversity, Exploitation and Conservation (MARBEC), University of Montpellier, CNRS, IRD, Ifremer, Montpellier, 34095, France 4IUT Sète, Univ. Montpellier, Sète, France 5UMR Marine Biodiversity, Exploitation and Conservation (MARBEC), CNRS , IRD, Ifremer, Sète, France 6Centre de Recherches Océanologiques (CRO), Abidjan, Côte d’Ivoire [email protected] Abstract: Sardinellas have been studied globally for microplastics and the associated ecological risks. However, the process of processing the fish before consumption, particularly in some West African countries, has not been sufficiently taken into account. In order to characterise the microplastics ingested by sardines consumed in Côte d'Ivoire, a total of 180 fish were sampled, of which 90 were sourced from local fisheries and 90 were imported 25 products from Senegal.. In each group, 30 fish were frozen, while 60 were smoked at 100°C for 3 hours. Then, 30 fish from each batch were removed to form the smoked fraction, while the remaining 30 were dried at 60°C for 72 hours, thus creating the smoked and dried fraction. The digestive tracts of each fish were isolated and digested using a potassium hydroxide solution (10%) to extract anthropogenic debris. Morphological identification and physico-chemical analysis using Fourier-transform infrared spectroscopy were carried out to determine the type of polymer present. In total, 845 pieces of debris were extracted from the sardines, with a higher proportion found in local fish (59.06%) based on their origin. Regarding the processing of the fish, fresh fish had a higher number of debris compared to smoked and dried fish, with no significant difference observed between the latter. The observed morphotypes were primarily composed of blue filaments. Among the 845 debris items analysed so far, 113 were identified as plastic, representing either 12% or 1.68±0.51 MP per individual. The plastics were predominantly polyethylene terephtalate (64%), followed by polypropylene (9%), polyester (8%), polyamides and polyvinyl chloride (5%), polyethylene (4%) Polyméthylméthacrylate and polyacrylonitrile (2%) and polystyrene (1%). These results will provide additional information on the state of pollution along the Ivorian coasts and the risks faced by local populations. Keywords: Plastic pollution, microplastics, marine biodiversity, Sardinellas, Ivory Coast. Vulnerability of the Ivorian-Ghanaian upwelling to climate change in the northern Gulf of Guinea KONE Kanakounou Jean-Marie1, KONE Vamara2, ABOYA Narcisse3, ANOH Kouassi Paul3 1Centre de Recherche Océanologique 2Université Polytechnique de San Pedro 3Université Félix Houphouët Boigny Abidjan Correspondance : KONE Kanakounou Jean-Marie « [email protected] » [email protected] [email protected] [email protected] Abstract: Over the past ten years, the central-eastern Atlantic (0-10° north), and more specifically the northern Gulf of Guinea, has been characterized by a significant warm anomaly, with temperatures fluctuating between 30 and 31°C during the January-May period. Coastal climatology and oceanography have been profoundly altered, with significant repercussions on the Ivorian-Ghanaian upwelling and fisheries productivity. The objective of this study is to understand the decadal trend of the Ivorian-Ghanaian upwelling in relation to the vulnerability of fisheries associated with the Ivorian and Ghanaian coasts. Among the various approaches necessary to achieve this objective, the first is the collection of characteristic data on upwelling systems, namely temperature, which is not only the main indicator of climate warming, but also salinity, which is a trace parameter of upwellings. In addition to these data, pH and dissolved oxygen levels are also considered, along with oceanic structures such as the vertical variation of the thermocline and the halocline. Analyzing the spatiotemporal dynamics of these parameters will allow for upwelling mapping and the construction of mediumand long-term upwelling projection models. The start and end dates, and therefore the duration, of upwelling 32 FLOOD RISK MAPPING IN WEST AFRICAN ESTUARY ENVIRONMENTS: THE EXAMPLE OF THE CASAMANCE RIVER DELTA, SENEGAL Tidiane SANE, Bouly SANE, Mamadou THIOR, Alexandre BADIANE, Cheikh FAYE, El Hadji Balla DIEYE Département de Géographie, UFR Sciences et Technologies, Université Assane Seck/Ziguinchor (Sénégal), [email protected] Abstract : Extreme weather events, such as floods, often occur at multiple spatial scales and sometimes have significant consequences. The Casamance Delta, with its low-lying topography and dense hydrographic network, is particularly vulnerable to seasonal flooding, especially as climate change affects both the watersheds and the adjacent plains. This study aims to assess flood risks and model the hydrological response of the Casamance River Delta management unit in the context of global change. To conduct this study, a diversified methodological approach was adopted to understand and analyze the hydrological response. Using spatial analysis and remote sensing tools, seven parameters derived from geological, hydrogeological, morphometric, rainfall, land-use, and topographic data were used to assess flood zones. These parameters were supplemented by surveys of 120 households to gather their opinions on the environmental changes observed due to recent climate dynamics. The results indicate spatial variability in flood risk levels across the delta. The highest risk of flooding occurs in low-lying areas, primarily where the river valleys (minor and middle channels) are located. Spatial distribution maps of the indices indicate that the areas most exposed to flood risk are those situated at the land-ocean interface. Therefore, strengthening infrastructure near vulnerable sites must be a priority to protect rice-growing lands and reinforce flood resilience in Lower Casamance. Keywords : Flood risk, Mapping, Casamance River Delta, Climate change, Vulnerability. The Saytoukat Géej, a citizen network monitoring marine pollution in Senegal Pape Sega Ndiaye, Amadou Ba, Marlène Menoux, Agathe Leroux, Marc Valmassoni, Babacar Thiaw, Claire Stragier ([email protected]) Abstract: Faced with worsening marine pollution along the Senegalese coast, Surfrider Foundation Senegal launched an innovative citizen science initiative: Saytoukat Géej, or “Guardians of the Ocean” in Wolof, a citizen-led environmental monitoring network focused on water quality and coastal waste. This network was established as a pilot project in Dakar in 2023, as part of Surfrider Foundation Senegal’s Water Quality Program. It addresses an urgent issue identified by local stakeholders : the degradation of water quality along the Dakar coastline, which threatens recreational activities and ecosystems. This program, carried out in partnership with the Ministry of the Environment and Ecological Transition, the City of Dakar, the Ouakam municipality, the Pasteur Institute of Dakar, Surfrider Foundation Europe, GRET, and the French Research Institute for Development (IRD), aims to enable water sports activities 33 without health risks while sustainably preserving the Senegalese coastline. Between June 2023 and December 2024, six strategic sites on the Dakar peninsula (Yoff, Ngor, Ouakam, Baie des Carpes, Secret, and Virage) were selected to test this operational model. A network of 23 committed citizens—surfers, lifeguards, fishermen, municipal employees, etc.—was trained in the environmental sampling protocol, developed in collaboration with the Pasteur Institute of Dakar and Surfrider Europe. The Saytoukat Géej conduct regular water sampling campaigns at each site. For each sample, observed data (temperature, tide, water appearance, presence of waste, etc.) are entered via a dedicated mobile application. The samples are then analyzed by the Pasteur Institute of Dakar to detect E. coli and enterococci bacteriological parameters. To date, more than 385 samples have been collected, allowing for the assessment of water quality according to European standards (Directive 2006/7/EC), in the absence of national standards in Senegal. This data collection has enabled the classification of certain sites as potentially "at risk." Beyond data collection, the program relies on participatory governance, structured around local coalitions in each community (community representatives, elected officials, nautical clubs, lifeguards, etc.) and a National Dialogue bringing together institutional, technical, economic, and community stakeholders. This framework fosters the co-creation of solutions, their local ownership, and their long-term implementation. Eighty-nine stakeholders were mobilized during the pilot phase. This pioneering approach fully illustrates the value of participatory science: producing reliable data, strengthening local capacities, bridging the gap between different levels of governance, and supporting evidence-based advocacy. By involving citizens from the initial assessment stage, the program empowers them to take concrete action, while facilitating the implementation of sustainable and shared solutions to protect the Senegalese coastline. Following the success of the pilot phase, the objective is now to integrate coastal waste monitoring and extend the network to other sites, in Dakar and beyond. This success confirms the relevance of citizen networks for environmental monitoring. In collaboration with the National Coastal Observatory, the Saytoukat Géej model can be deployed nationwide, with enhanced value and accessibility to the data produced. 34 Biogeochemical Challenges in the Gulf of Guinea: Monitoring, Key Projects, and Multidisciplinary Approach ANSELME CREPIN MAMA Association of Professionals in Coastal and Aquatics Management APCAM, Maritime Technics Institute, Cameroon Abstract: The Gulf of Guinea faces major biogeochemical challenges, studied by recent research highlighting the influence of temperature, salinity, nutrients, and dissolved oxygen on primary production. These parameters have been systematically monitored for several years (salinity, dissolved oxygen, and nutrient data since 2004; phytoplankton pigments since 2011; marine pH since 2021), forming a valuable database. Current research also explores the impact of the carbonate system and nutrient chemistry on phytoplankton. To address these water quality challenges, two key projects are emerging: the Global Estuaries Monitoring (GEM), which establishes a standardized framework for global estuarine monitoring, and GEM-in-a-Box, a modular and accessible solution to facilitate the deployment of monitoring systems in various estuarine environments. Resolving these biogeochemical issues requires a multidisciplinary approach, bringing together scientists, policymakers, and local communities for the sustainable management of the region's marine and coastal ecosystems. Keywords: Biogeochemical Challenges, Gulf of Guinea, Monitoring, key projects, Multidisciplinary Approach Will Douala’s Coastland sink faster than sea-level rise? Investigating coastal subsidence and relative sea-level rise until 2050. Chounna Y. G.1,2*, Minderhoud P.S.J.2,1,3 & Teatini P.1 1. Department of Civil, Environmental, and Architectural Engineering, University of Padova, Padova, Italy. 2. Soil Geography and Landscape group, Wageningen University, Wageningen, The Netherlands. 4 3. Department of Subsurface and Groundwater Systems, Deltares Research Institute, Utrecht, The Netherlands e-mail: [email protected] Abstract:Rapidly growing coastal cities along the Gulf of Guinea are increasingly exposed to geoenvironmental hazards, including coastal erosion, sea-level rise, and land subsidence. One of these increasingly impacted cities is Douala in Cameroon. In Douala, rapid urban expansion has intensified environmental stress, contributing to accelerated land subsidence in vulnerable zones, with InSAR-estimated rates averaging -2.7 mm/year and reaching -17.6 mm/year in some areas between 2018 and 2023. These processes are largely driven by land-use changes, and high rates are mainly attributed to the urbanisation of croplands and wetlands. 35 With Douala’s population expected to double by 2050, ongoing land-use changes, urbanisation, and related increased groundwater extraction are likely to exacerbate land subsidence risks. Despite this, the ability to understand, project, plan, and integrate future land subsidence into urban planning strategy remains limited due to data gaps and underdeveloped modelling approaches. This study attempts to address the knowledge gap by applying Singular Spectrum Analysis (SSA) to InSAR-derived land subsidence time series (2018–2023) to extract dominant trend components. A statistical modelling framework is then used to identify the best-fitting function (linear, polynomial, or exponential) for each measurement point. These models are applied to project cumulative land subsidence across Douala until 2050. The projected cumulative land subsidence is combined with projected sea-level-rise values (SSP1-SSP5) and up-to-date highresolution elevation assessments to assess the future exposure of the Douala Coastland. Our results provide estimates of relative sea-level rise for Douala up to 2050 and provide valuable insights for urban planning and coastal resilience strategies of the Gulf of Guinea’s sinking cities. Keywords: Coastal Subsidence, Coastal Vulnerability, Urban Adaptation, Relative Sea-Level Rise How relocation in the face of coastal risks shapes senses of place and well-being? The case of a coastal community in Saint-Louis, Senegal. Clara Therville, Kardiatou Samba Sall, Absa Diop, Sambou Ndiaye, François Bousquet, Elhadji Sow, Boubou Aldiouma Sy Abstract: In a context of climate change and high demographic pressure along the coasts, coastal management has to face increasing coastal risks, and deal with the relocation in emergency of thousands of people in Africa. Through this process, hard-infrastructures such as dykes are promoted in the short-term when funding is available, but the relocation is presented by some stakeholders as unavoidable and necessary to protect people from coastal risks. However, communities’ dependence and attachment to place, as well as their social organization, is rarely considered – just as the renewed vulnerabilities induced by relocation. In this talk, we present the results of a survey conducted among 160 members of a coastal community in Senegal – strongly culturally and economically attached to the sea. While 80 of them have lost their homes during a submersion in 2018 and have been relocated 8km far from the coast, another 80 still live behind a dyke inaugurated in 2023, but should be relocated by 2025. In this context, we study how well-being and senses of places have evolved for both communities, as well as their acceptance and involvement in coastal management policies. We highlight how relocation in emergency reinforced the feeling of attachment to the coast, impacted well-being, and reveals fears, hopes and uncertainties about the future. We discuss the negotiations and tensions that occurred between communities and the project promoters. We open a discussion on the role of social researchers and on the mobilization of 36 transdisciplinary approaches – especially using participatory theater – to reveal such dynamics and support more inclusive approaches of coastal risks management. 37 2021-2030 United Nations Ocean Decade - Support & Opportunities for Africa Dramé A. B.1-2 1 United Nations Ocean Decade Advisory Board, Paris, France 2 CoastGIS Research Institute, Cabo Verde & Senegal, [email protected] Abstract: Marine and coastal systems are at the forefront of the Anthropocene, undergoing transformations fuelled by increasing human pressure and climate variability. The growing influence of human development and intervention on marine ecosystems has led to a global environmental crisis, particularly in tropical or low-lying environments and island states, affecting the evolution of estuaries and coastal areas, as well as marine biodiversity. In West Africa, low-lying coasts account for approximately 56% of the GDP and 31% of the urban population. Nevertheless, ocean sciences in the region face significant constraints, including limited data availability, insufficiently skilled human resources, and underrepresentation in international collaborations and decision-making processes, which hinder progress toward inclusive and sustainable ocean governance. This work presents the United Nations Ocean Decade of Ocean Science for Sustainable Development (2021–2030), the largest coordinated ocean science movement, led by the UNESCO-IOC (Intergovernmental Oceanographic Commission), launched in 2021. It focuses on Africa’s engagement in the UN Ocean Decade through National Decade Committees and presents capacity-building and funding opportunities through philanthropic organisations and strategic partnerships. It also highlights ongoing and upcoming calls for applications. Ultimately, it provides opportunities to strengthen and scale up scientific collaboration in the realm of ocean sciences, bringing together the UN system, coastal communities, academia, and governments to advance shared global goals for climate resilience, marine biodiversity conservation, and human well-being in line with the 2030 Ocean Vision.