Spatiotemporal Assessment of Landsat derived Normalized Difference Vegetation Index (NDVI) for Forest degradation in Afaka Forest Reserve, Kaduna Nigeria.

Abstract

Urbanization and agricultural intensification, driven by population growth and lacking adequate management have heightened forest degradation risks. This study aims to assess spatio-temporal Landsat-derived Normalized Difference Vegetation Index (NDVI) for vegetation degradation. Supervised classification was used for NDVI analysis of Landsat imagery from 1986, 1999, and 2018 for Afaka Forest Reserve, with a 30 m resolution using Erdas Imagine 9.2. The results show the vegetation cover decreased by -3.83% from 1986 to 1999, but slightly increased by 1.69% from 1999 to 2018. The water body class decreased by -0.71% from 1986 to 1999 and slightly increased by 0.04% from 1999 to 2018. Overall, the non-vegetation cover increased by 0.14%, while vegetation and water bodies decreased by -0.11% and -0.04%, respectively. The relationship between climate characteristics and mean NDVI values shows a positive correlation (0.77), implying a direct impact of climate on forest cover. The decrease in vegetation cover and water bodies indicates a decline in forest resources, while the increase in non-vegetation class suggests the expansion of built-up areas, light forests, and bare surfaces. These changes provide clear evidence of vegetation degradation attributable to anthropogenic factors as well as natural factors (climate change). The study recommends a forest ecosystem restoration approach through forest governance and strengthened enforcement of strict conservation measures, adopting climate-adaptive and community-based forest management for sustainability.