Écologie et dynamique spatio-temporelle des mangroves au Togo

In Togo, the building of harbor facilities, the construction of the hydroelectric dam plant of Nangbeto, urban growth and activities relating to the installation of fish farms, and the expansion of croplands are the major causes of a drastic degradation of mangroves. For a better management of this ecosystem, assessment of the current structure of mangroves, their spatiotemporal dynamics and socioeconomic issues related to mangroves were performed. Data from forest inventory, structured interviews and Landsat images of 1986 and 2014 were used. Inventories have identified 23 plant species distributed among 23 genera and 17 families dominated by Rhyzophora racemosa and Avicennia germinans. The hierarchical classification of forest inventory samples has identified three groupings of mangrove plants. Investigations show that stakeholders use wood from the mangrove for energy and fuelwood purposes. From 1986 to 2014 the land use/land cover patterns in the study area has undergone tremendous changes. Floodplains and tannes find their areas increased by 39.91 % and 46.06 % respectively, while wooded vegetation cover in whole lost 47.19 % of its area. Anthropogenic pressures would be the main cause of the degradation affecting mangroves ecosystem services and productivity. However, due to the ecological importance of mangroves, there is a need for an appropriate management plan including the contextual realities of mangroves landscapes

Écologie et dynamique spatio-temporelle des mangroves au Togo

Au Togo, l’installation des ouvrages portuaires, la construction du barrage hydroélectrique de Nangbéto, la croissance urbaine et les activités relatives à l’installation des bassins piscicoles, et l’expansion des aires de production en agriculture sont les causes majeures de la dégradation drastique des mangroves. Afin de contribuer à une meilleure gestion de cet écosystème, une évaluation de la structure actuelle des mangroves, de leur dynamique spatio-temporelle et des enjeux socio-économiques a été réalisée. Pour ce faire, des données d’inventaires forestiers, d’entretiens dirigés et des images Landsat de 1986 et de 2014 ont été utilisées. Les inventaires ont permis de recenser 23 espèces végétales réparties en 23 genres et 17 familles dominées par les Rhyzophora racemosa et Avicennia germinans. La classification hiérarchique des relevés d’inventaire forestier a permis d’identifier trois groupements végétaux de mangroves. Les résultats des enquêtes montrent que tous les acteurs utilisent le bois provenant de la mangrove pour des besoins énergétiques et de service. De 1986 à 2014, l’état des unités d’occupation du sol de la zone d’étude a subi d’énormes mutations. Les zones inondables et les tannes ont vu leurs superficies augmentées respectivement de 39,91 % et 46,06 % tandis que le couvert de végétation dense a perdu globalement 47,19 % (soit 829,82 ha) de sa superficie. Les pressions anthropiques seraient à l’origine de la dégradation des mangroves, impactant les services écosystémiques ainsi que leur productivité. Du fait de l’importance écologique des mangroves, il est urgent et nécessaire d’élaborer un plan d’aménagement adéquat prenant en compte les réalités actuelles.In Togo, the building of harbor facilities, the construction of the hydroelectric dam plant of Nangbeto, urban growth and activities relating to the installation of fish farms, and the expansion of croplands are the major causes of a drastic degradation of mangroves. For a better management of this ecosystem, assessment of the current structure of mangroves, their spatiotemporal dynamics and socioeconomic issues related to mangroves were performed. Data from forest inventory, structured interviews and Landsat images of 1986 and 2014 were used. Inventories have identified 23 plant species distributed among 23 genera and 17 families dominated by Rhyzophora racemosa and Avicennia germinans. The hierarchical classification of forest inventory samples has identified three groupings of mangrove plants. Investigations show that stakeholders use wood from the mangrove for energy and fuelwood purposes. From 1986 to 2014 the land use/land cover patterns in the study area has undergone tremendous changes. Floodplains and tannes find their areas increased by 39.91 % and 46.06 % respectively, while wooded vegetation cover in whole lost 47.19 % of its area. Anthropogenic pressures would be the main cause of the degradation affecting mangroves ecosystem services and productivity. However, due to the ecological importance of mangroves, there is a need for an appropriate management plan including the contextual realities of mangroves landscapes