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Mangroves and Climate Action: Unlocking Africa’s Nature-Based Potential in a Changing Climate

par Ofori, Samuel
Président du jury Stiers, Iris
Promoteur Dahdouh-Guebas, Farid
Co-Promoteur Huge, Jean
Publication Non publié, 2025-09-09

Thèse de doctorat

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Résumé :

In an era of increasing change in climate, the warming on the African continent is projected to be higher than the global average, with an increased average temperature of 3–4 °C by the end of the 21st century under a high Representative Concentration Pathway. It is understood that the continent is among the least contributors to the global greenhouse gas emissions, yet among the most vulnerable regions to the impacts of climate change. Mangrove ecosystems are well-placed as key nature-based solutions to climate change and Africa hosts 20% of their global extent. In this study, we sought to evaluate how African countries can leverage the climate benefits mangrove ecosystems present to advance their climate actions. Firstly, we conducted a systematic review on the Nationally Determined Contributions (NDCs) of 33 African countries possessing mangroves by assessing their level of integration of mangrove ecosystems into their NDCs. The findings reveal that countries like Equatorial Guinea, Nigeria, Senegal, and Sudan have taken commendable steps in integrating mangroves within their NDCs, showing leadership among the other countries. Subsequently, we used Ghana as a model country to demonstrate how a mangrove-possessing country in Africa can leverage its mangrove ecosystems for climate action. We first conducted a systematic literature review with field data collected to evaluate the structure, services, drivers, and governance of Ghana’s mangrove ecosystems. The findings from this study revealed that Ghana’s lack of a mangrove ecosystem management strategy has resulted in the massive decline in its mangrove extent. To better understand and map the extent of Ghana’s mangrove decline, we used remote sensing and GIS methods to assess the spatio-temporal changes of Ghana’s mangrove ecosystems from 2015 to 2024 and the factors causing these changes. The results showed that Ghana's mangrove extent had declined by 15.4% from 2015 (68.41 km2) to 2024 (57.87 km2). The findings further demonstrate the need for countries to develop national mangrove maps rather than depending on global mangrove extents, which are often inaccurate. For countries to be able to develop effective mangrove actions towards climate change mitigation, we conducted in-situ sediment sampling from the Kakum mangrove forest to examine the role of spatio-temporal variations of environmental factors on the carbon dynamics of mangroves. Key findings include the significant positive effects of salinity and dissolved oxygen on trap organic matter and pH as the only predictor having a significant but negative effect on bottom organic matter. These findings present an opportunity for countries to accurately assess the carbon storage potential of their mangrove ecosystems and identify restoration areas with high carbon storage potential. The findings from this thesis provide perspectives and recommendations for stakeholders (scientists, non-governmental organizations, governments, and local communities) involved in mangrove ecosystem use and management in Ghana and beyond to work together to effectively harness the immense climate benefits their mangrove ecosystems present.