Impacts of land cover changes on desertification in northern Nigeria and implications on the Lake Chad Basin

摘要

Desertification is an issue of environmental concern in Nigeria, particularly the northern part of the country. This study examines land cover changes related to the process of desertification in the states along the northern boundary of Nigeria (Sokoto, Zamfara, Katsina, Jigawa, Yobe, and Borno) and the implications on the Lake Chad Basin. A time series of Landsat imagery at a spatial resolution of 30 m was used over the period from 1984 to 2016. The imageries were subjected to maximum likelihood classification for the purpose of extracting the land cover and analysing the change. Also, the areal extent of vegetation cover within the 32-year period was calculated annually. Using Pearson's correlation analysis, the relationship between the vegetation cover and rainfall was assessed as well as temperature and population density. Results show that 45,945.08 km(2) of vegetation cover was lost within the study area including the Lake Chad area between 1984 and 2016. The annual rate of change varied across the different feature classes; the built-up area had the highest rate of increase of 13.68% and 2.65%, from 1984 to 2000 and 2000-2016 respectively. Bare-land increased at the rate of 0.96% and 0.28% from 1984 to 2000 and 2000-2016 respectively while vegetation had the highest rate of decrease of 2.18% and 2.02% from 1984 to 2000 and 2000-2016 respectively. A pattern of vegetation loss was observed as a large expanse of vegetation cover was lost across the north-west and the north-east regions including the Lake Chad area. It was also shown that the magnitude of vegetation cover correlated negatively with temperature and population density but with no significant correlation with the rainfall. The study recommends that the Federal Government should ensure the full implementation of the Great Green Wall project which is aimed at mitigating the rapid sprawl of natural land degradation processes and desertification in the northern boundary states.