Assessing the impacts of land use on riparian vegetation dynamics in Osun State, Nigeria

Abstract

The existence of riparian vegetation is greatly threatened by change in land uses in Nigeria and information on historical management of land use which influences riparian vegetation dynamics is critical to the conservation of plants species diversity. This information is poorly understood especially in Nigeria and by extension in Africa. This study therefore assessed the areas covered by riparian forests in Osun State, Nigeria in order to identify the main drivers of its decline using optical remote sensing data. It also assessed the availability and distribution of the riparian forests over three decades (1986–2016) using Landsat Enhanced Thematic Mapper (ETM). Results showed that the riparian forests covered 546.18km2 (6.40%) with about 308riparian forests distributed across the state in 1986 but had declined to 176 by 2016. Three decades later, areas covered by riparian forests decreased to171.69km2 (2.01%), representing a decline of about 69% and was predicted a rapid transition to disturbed lands. Human activities such as logging, farming, grazing and construction have greatly influenced the riparian vegetation cover with obvious decline in extent, distribution and quality. Observation from our case study showed that the disappearance of these forests is taken place at a rate that is faster than the predicted level of the Nigerian riparian forest loss by 2040. Notably deforestation, agriculture and urbanization are the main drivers of this decline, of the African gallery forests.