Land Cover Dynamics Associated with the Spatial Changes in the Wetlands of Lagos/Lekki Lagoon System of Lagos, Nigeria

Abstract

Obiefuna, J.N.; Nwilo, P.C.; Atagbaza, A.O., and Okolie, C.J., 2013. Land cover dynamics associated with the spatial changes in the wetlands of Lagos/Lekki Lagoon system of Lagos, Nigeria. Urban sprawl is one of the severe land use/land cover (LULC) change agents, especially in rapidly urbanizing developing countries such as Nigeria. Land use/land cover is among the key drivers of environmental change as it leads to dramatic changes in both landscape patterns and ecosystem functions. Lagos metropolis, the nation's economic nerve center, is on a low-lying coastal landscape endowed with lagoons, wetlands, and other ecological assets. The Lagos/Lekki Lagoon system, with its catchments and wetlands, constitute about 71% of the state. With rapid urbanization and intense development pressure, some of the fringing wetlands and other land cover in the area have been converted to urban landscape. Just like the wetlands, the precise nature of these land cover changes is comprehensively unknown. In this ongoing study, land cover dynamics linked to the spatial changes in the wetlands fringing these lagoons are also comprehensively assessed. With low topography, high energy, and erosive coastlines, the extent of coastal erosion (1985–2009) in the area is assessed with remote sensing data and geographic information system (GIS) using topographic maps as baseline data. ENVI software is deployed for the processing of Landsat imageries, and unsupervised classification is used for image classification. The objective is to establish the locations and magnitude of the land cover dynamics between 1984 and 2006, ultimately leading to implications for flood risk on affected areas. Results show that as swamps decreased from 344.75 km2 to 165.37 km2 and mangroves decreased from 88.51 km2 to 19.95 km2, both between 1984 and 2006, built-up areas increased from 48.97 km2 to 282.78 km2 at 10.61 km2/y; water body decreased from 685.58 km2 to 654.98 km2 at −0.16 km2/y; bare land increased from 24.32 km2 to 72.73 km2 at 2.2 km2/y; and vegetation decreased marginally from 1369.15 km2 to 1361.08 km2 at −0.37 km2/y all between 1984 and 2006. Evidently most of the growth in built-up areas occurred in previous wetland areas and some vegetated areas. Most of the increase in built-up area occurred in the Eti-osa Local Government Area (LGA) and then in the Kosofe LGA. The decrease in the water body is attributable to anthropogenic action of reclamation and accretion arising from island formation on the Lekki Lagoon. Some of the consequences of the land cover (LC) dynamics are briefly highlighted.