Application of remote sensing to a studies of urbanisation and wetland changes in West Africa: the experience of the Lagos Region (Nigeria)

Using Remote sensing technique, wetlands/wetland changes relative to other land use changes were examined in two urban centres of West Africa (Lagos metropolitan area and Ikorodu), both in the Lagos region (Nigeria). The main categories of the landuses identified in the study areas include the built-up areas, agricultural lands, wetlands (vegetated and unvegetated) and the water bodies, in addition to barren lands. Data generated using the 1962 and 1983 photographs for the Ikorodu area, and 1971 photograph and 1994 imagery for the Lagos Metropolitan region were used for the study. Detailed illustrations were given, using the Lekki Peninsula and Festac Town (both in Lagos metropolitan area), and Ikorodu, a smaller urban settlement in the Lagos region were used.

The study showed that very high change of more than 80% reduction in wetlands were characteristic of the Lekki Peninsula and the Festac Town within the Lagos Metropolitan area. Although, the reduction of wetlands in the Ikorodu area of Lagos region was less, it was also significant. In particular, between 1962 and 1983, the vegetated wetlands were reduced from 1773 ha in 1963 to 1458 ha in 1983. A detailed analysis of the change shows that the percentage change in swamps and marshes, about 15%, was more than that of the forest wetlands with about 9%. A comparison of the wetland changes in the study locations with other land use changes show that the changes in the wetlands were mostly due to rapid growth in the urban centres in all the locations with additional impact of increase in farmlands especially in the Ikorodu area. For example, in the Ikorodu sector of the study area, built-up areas increased by more than 600% from about 82 ha. In 1963 to about 573 ha in 1983. In contrast, farmlands increased by about 13% from about 1419 ha to about 1597 ha. The implications of the changes in wetlands in the areas of study for the components of the energy and water balances are discussed.