Spatio-temporal Patterns of Normalised Difference Vegetation Index Trends in Parts of Northern Nigeria

Abstract

Vegetation cover change has been, and still is a problem in Nigeria. The main objective of the study is to assess Spatio-temporal variability of vegetation cover in parts of Northern Nigeria using remotely sensed SPOT VEGT data sets. The data covers between 1999 and 2018 and consists of 10-day synthesis NDVI (S10) data. The maximum value composite technique was used to remove atmospheric moisture, cloud and simple haze in the imageries. The 10 days, monthly and later annual composites were generated in image calculator tool in IDRISI selva 17.0 software. Time series trend analysis was performed to determine the Spatio-temporal trends of the annual NDVI. The annual composites were imported into GIS environment to analyse spatial variations of NDVI in the study area. The composite of 2011 was noisy hence was not used in the analysis. The result indicated that NDVI is characterised by moderate Spatio-temporal heterogeneity. The relatively high value of NDVI (above 0.4) is mainly distributed in Jos East, Riyom, Bokkos which are located south of the area while the low value (slightly below 0.3) is obtained in Gamawa Gurri and Ringim. Furthermore, significant positive trends in overall greenness were observed in the southern region while negative trends are also present in the north. This study recommended studies on vegetation dynamics (with climate and anthropogenic influences) with high-resolution satellite data to remove the uncertainties associated with coarser resolution remote sensing-based vegetation data.

Keywords: vegetation cover, Spatio-temporal, time-series imageries, NDVI