ASSESSMENT OF VEGETATION HEALTH IN OIL SPILL-AFFECTED AREAS USING REMOTE SENSING AND GIS: A CASE STUDY OF OBIO/AKPOR LGA, RIVER STATE

Vegetation plays a critical role in maintaining ecological balance, protecting biodiversity, and supporting human livelihoods. However, in the Niger Delta region of Nigeria, oil spill incidents and rapid land use changes have continued to threaten vegetation resources. This study assessed the impact of oil spills on vegetation health in Obio/Akpor Local Government Area (LGA), Rivers State, using Remote Sensing and Geographic Information System (GIS) techniques. The research focused on detecting changes in vegetation condition over a twenty-year period, between 2003, 2013, and 2023, by analyzing satellite-derived vegetation indices. Landsat imagery for the three study years was acquired and processed using ArcMap software. Six vegetation indices were computed to measure different aspects of vegetation health: Normalized Difference Vegetation Index (NDVI) for greenness and biomass, Soil Adjusted Vegetation Index (SAVI) for soil-corrected greenness, Moisture Stress Index (MSI) for water stress, Normalized Difference Water Index (NDWI) for wetland and water-related vegetation, Shortwave Infrared (SWIR) for canopy moisture, and Green–Red Vegetation Index (GWIR) for chlorophyll activity. Buffer analysis was applied around oil spill points to compare impacted and control areas. Zonal statistics were then used to quantify vegetation health across time. The results revealed a progressive and continuous decline in vegetation health across Obio/Akpor LGA. NDVI analysis showed that healthy vegetation cover reduced from about 68% in 2003, to 50% in 2013, and further down to 38% in 2023. SAVI followed the same trend, while MSI values increased significantly, indicating a sharp rise in moisture stress within oil spill zones. NDWI values dropped from 25% in 2003 to 12% in 2023, confirming the shrinkage of wetlands and water-related vegetation. SWIR and GWIR also recorded strong declines in canopy moisture and photosynthetic activity, especially in spill-impacted areas. Comparisons between control and impacted sites showed that oil spills caused long-term and cumulative vegetation stress, while control sites maintained relatively stable vegetation health. Overall, this study confirms that oil spills, urban expansion, and land use change are the major drivers of vegetation decline in Obio/Akpor LGA. The findings highlight the need for effective environmental monitoring, oil spill remediation, and sustainable land management practices to protect vegetation resources and restore degraded ecosystems in the Niger Delta. Keywords: Remote Sensing, GIS, Vegetation Indices, Oil Spills, NDVI, SAVI, Obio/Akpor LGA, Niger Delta