Four Decades of Cover Change, Degradative, and Restitution Stages of Mangrove Forest in Douala-Edea National Park, Cameroon

Abstract

Mangroves are valuable ecosystems that provide significant biological, environmental, ecological, and cultural functions. To inform the development of management plans for the ecosystem's sustainability, it is crucial to evaluate how their land cover, levels of degradation, and phases of restitution have changed. GIS and remote sensing techniques were used to classify, and analyze Landsat images from 1980 to 2022 categorized into nine classes: bare ground, Nypa palms, settlements, coastal sedimentation, river sedimentation, regeneration, matured mangroves, dense forest, and water body. Using the Markovian chain approach, the changes noted during the period were utilized to forecast future trends up to 2052. Findings demonstrated that the mature mangrove area decreased throughout the study. The surface area covered by mature mangroves was 80628.78 hectares in 1980, which decreased by 7.31%, 1.51%, 3.70%, and 5.06% in 1990, 2000, 2010 and 2022 respectively and by 17% for the overall period of 42 years. Additionally, gains of 4.07% from 2000 to 2010 and 6.84% from 1980 to 2022 were observed probably from artificial mangrove regeneration. Settlements, invasive Nypa palms, bare ground (resulting from over-exploitation), and sedimentation of rivers and coast primarily replaced mangroves. The prediction derived indicated the continuous decline in mangroves if not fully protected by law. These results provide vital information to direct future mangrove conservation actions in the recently gazetted Douala-Edea National terrestrial and marine Park and other mangrove blocks along the Gulf of Guinea.