MODIS NDVI assessment of forest degradation in the federal capital territory Abuja, Nigeria, Sub Saharan Africa: A case study of the year 2000 – 2022

Abstract

The Federal Capital Territory (FCT) Abuja is one of Africa's fastest-growing cities, and its rapid, unsustainable growth has led to forest degradation. This study aims to assess changes in Abuja's forest cover from the year 2000 to 2022 by analyzing annual averages of the Normalized Difference Vegetation Index (NDVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data. The data extraction and processing were conducted via JavaScript code editor on the Google Earth Engine (GEE) platform and ArcGIS 10.7.1. The user's accuracy (UA), producer's accuracy (PA), overall accuracy (OA), and kappa coefficient (KC) of the
classified NDVI maps were computed via ArcGIS 10.7.1 and Google Earth Pro. The OA for 2000 and 2022 were 90% and 93%, respectively. The KC were 0.85 and 0.90, respectively. In the year 2000, the maximum value of the NDVI was 0.713, while the minimum value was -0.01. On the other hand, in the year 2022, the maximum value decreased to 0.634, while the minimum value increased to 0.05. A reclassified map was created using the NDVI threshold from the raster image. The NDVI threshold value was able to identify areas with no vegetation, sparse vegetation, or dense vegetation, which are the land cover classes considered in this study. In 2000, areas with no vegetation occupied 8 km², which later increased to 53.2 km² in 2022. Sparse vegetation occupied an area of 3,411 km², which later increased to 6,905 km² in 2022. Furthermore, in the year 2000 dense vegetation occupied an area of 3,936 km², which later decreased to 388 km² in the year 2022, which indicates massive forest degradation. The findings of this study have practical applications in the fields of environmental monitoring and forest management in FCT, Abuja, enabling policymakers to promote sustainable development.