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Using historic archives and recent remote sensing imagery to study long-term spatio-temporal dynamics of mangrove forests surrounding Bajul, in The Gambia.

par da Mota Oliveira, Izabel
Promoteur Dahdouh-Guebas, Farid
Co-Promoteur Behara, Satyanarayana ;Scheper, Lennert;Van Der Stocken, Tom
Publication Non publié, 2024-08-29

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Résumé :

Mangrove ecosystems provide important socio-economic benefits to local communities and increasedawareness and monitoring data has driven long-term mapping and monitoring initiatives. However, adisconnect between the initial impact on the ecosystems and its systematic monitoring creates gaps inthe understanding of mangrove spatio-temporal dynamics. These gaps can be addressed through mixedmethods retrospective research beyond RS. In a case-study area Tanbi Wetland National Park (TWNP)regions in the Greater Banjul Area, The Gambia, this study evaluates the historical and recent changes inmangrove presence and extent by joining Landsat imagery (2023, 2013, 2003), historical aerialphotographs (1946, 1964, 1982, 1993) and archival records (1779-1949). Historical cartographic data,while varying in detail, scale and quality, indicate significant changes to mangrove presence due tourban expansion, particularly surrounding the city on Bathurst (now Banjul) and peri-urban mangrovesand to a lesser extent, agriculture. Time series analysis revealed a 10% reduction in mangrove areabetween 1946-2023, notably between 1946-1964 (-5.13%) and 2003-2013 (-6.9%). Conversely, therewere modest gains between 1982-1993 (+1.18%) and 2013-2023 (+4.09%). Despite these fluctuations,TWNP has remained relatively stable since 1816. Notwithstanding ongoing conservation and restorationefforts, the study highlights ongoing climate change vulnerability that affect local livelihoods and theTWNP.