Simulating the Movement of Desertification in Sokoto and its Environs, Nigeria Using 1 km SPOT-NDVI Data

摘要

This study simulates desertification in Sokoto and its environs using 1 km resolution Normalized Difference Vegetation Index (NDVI) data from the SPOT instrument. The data was downloaded as ten daily composites. The extracted data of the study area was clipped using the VGTExtract Software. The ten daily composites were initially recomposed to monthly and finally to 13 annual composites (time series) using Maximum Value Composite (MVC) algorithm within the Idrisi Andes GIS environment. The Multidimensional Choice (MDCHOICE) tool of Idrisi Andes was applied on the time series for temporal vegetation dynamism assessment while 1st and 2nd order surface trend fitting were carried out to assess the direction and pattern of desertification. Desertification was categorized by 1 standard deviation to the mean and temporal profiling was also carried out to probe into NDVI values of the time series at curious points. Results show that the inter-annual vegetation vigour exhibited a diminishing trend over the time series. The direction of desertification is North-West to South-East. Site 1 is located at Illela and Bamgi in Nigeria and Site 2 around Koukadin falling in Niger Republic are the worst affected by desertification within the study area. As desertification threatens human survival intensive tree planting around these areas in form of afforestation and establishment of more shelter belts and cattle ranches to curtail indiscriminate grazing, sensitisation of people towards being friendly with the environment and provision of alternative use of energy such as kerosene and gas for domestic uses at affordable prices as well as improvement in distribution and availability as immediate measures were recommended.