Spatio-temporal assessment of land use/land cover changes in onitsha, anambra state, south-eastern, nigeria: a comparative study of 2017 and 2024.

Land use and land cover in Onitsha, Anambra State, experienced substantial transformation between 2017 and 2024, driven by rapid urban expansion. Using Sentinel-2 satellite imagery and ESRI Land Cover Explorer data, this study assessed spatial and temporal changes across seven LULC categories: built-up area, trees, rangeland, cropland, water bodies, bare ground, and flooded vegetation. Built-up land increased from 35.17 km² (66.47%) in 2017 to 41.67 km² (78.76%) in 2024, recording a net gain of 12.29%. Tree cover declined sharply from 4.43 km² (8.38%) to 0.16 km² (0.31%), reflecting an 8.07% loss, while rangeland dropped by 3.7%, bare ground by 1.2%, and flooded vegetation by 0.05%. Cropland showed a marginal increase of 0.62%, and water bodies remained largely stable with a 0.11% gain. Change detection through post-classification comparison and transition matrices confirmed that built-up expansion occurred primarily at the expense of vegetated and undeveloped lands. Accuracy assessments produced overall classification accuracies exceeding 85%, validating the reliability of the results. The environmental consequences of this shift include elevated surface temperatures, increased flood risk, biodiversity loss, and reduced air quality. These impacts are closely linked to public health outcomes such as respiratory illnesses and heat stress, particularly in high-density zones. Recommendations include the integration of tree planting and green infrastructure into urban planning, the enforcement of land zoning regulations, and the removal of old and dilapidated buildings for conversion into ecological buffers. A participatory geospatial monitoring framework is also proposed, using open-access satellite data and mobile tools to engage local communities in tracking land changes. This study offers a replicable geospatial methodology for urban land monitoring using free, high-resolution datasets. The results provide critical insights for sustainable land management and urban policy in Onitsha, supporting climate adaptation, public health protection, and the achievement of Sustainable Development Goals 11, 13, and 15. By combining environmental analysis with actionable strategies, the study contributes to the development of resilient, livable, and ecologically balanced cities in Nigeria.